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Self-healing nanocomposite dna hydrogels with high mechanical strength
DNA hydrogels are promising soft materials because of the distinctive properties of DNA such as biocompatibility, coil-globule transition, molecular recognition, and selective binding. However, such hydrogels synthesized so far suffer from poor mechanical properties and low dimensional stability, which limit their stress-bearing applications. What is more, advanced technological applications demand more sophisticated properties for materials such as self-healing ability and high recovery after applying a load or exposing an external damage. In this thesis study, the focus is to resolve these disadvantages and propose a novel concept for the preparation of high-strength double-stranded (ds) DNA hydrogels with temperature sensitivity and self-healing ability. The hydrogels were synthesized by free-radical polymerization of N-isopropylacrylamide (NIPA) or N'N-Dimethylacrylamide (DMAA) in aqueous nanoclay (Laponite) dispersions containing ds-DNA between 2-8 w/v % which is assumed to be in a highly entangled state since the critical overlap concentration c* of ds-DNA is around 0.043 w/v %. The nanoparticles of synthetic nanoclay (Laponite XLG® or Laponite XLS®) act as a dynamic cross-linker to form a three-dimensional physical network due to strong clay-polymer interactions. We observed that ds-DNA maintains its native structure and function during the formation of nanocomposite hydrogels. The hydrogels prepared at various Laponite contents display the characteristics of both the polymers poly(N-isopropylacrylamide) or poly(N'N dimethylacrylamide) and ds-DNA e.g., temperature sensitivity, self-healing ability, highly strechability, denaturation and renaturation of DNA strands, and they exhibit a high tensile fracture stress and elongation to break. A systematic series of experiments were conducted throughout the thesis study. At first, the gelation kinetics and formation of the network structure of hydrogels were monitored by rheometry in order to understand the internal dynamics of this novel gel network structure. Rheological measurements revealed the opposite effects of DNA and Laponite XLG on the viscoelastic properties of hydrogels. Within the constructed gel network, XLG acts like a chemical cross-linker and promotes the elastic behavior of the hydrogels by increasing the modulus and decreasing the loss factor. In contrast, DNA contributes to their viscoelasticity and produces hydrogels with a lower modulus and a higher loss factor, suggesting the weakening of clay-polymer interactions in the presence of DNA. Following the formation of 3D gel network structure, frequency sweep test were carried out by rheometry under isothermal conditions in order to gain a deeper understanding about the internal microstructure of hydrogels. Consecutive measurements showed that at low frequencies, nanocomposite DNA hydrogels (NC-DNA)s exhibit a lower modulus and a higher loss factor as compared to the classical nanocomposite hydrogels that is the hydrogels without DNA, revealing energy dissipation. This energy dissipation on long experimental time scales is attributed to the weak clay/DNA interactions. ds-DNA molecules in the hydrogel could follow the slow oscillation and slip on the surface of the nanoparticles by dissipating energy. At high frequencies, tan δ of NC-DNAs' is similar to that of NCs', likely because the semiflexible ds-DNA with a persistence length of 50 nm could not move with a high frequency in the gel network. Cyclic heating/cooling experiments conducted between below and above the melting temperature of ds-DNA revealed a drastic increase in the elastic modulus of nanocomposite DNA hydrogels due to the thermally induced denaturation and renaturation of DNA within the physical network. Unzipping of the helices of DNA by applying a thermal energy above its melting temperature, allow to form additional cross-linking during the cooling period by constructing H bonds irregularly.For testing the temperature sensitivity, The gel samples were heated from 20 to 50 oC at a rate of 3.25 oC min-1 during which the changes in the dynamic moduli were monitored as a function of temperature. The elastic modulus G' rapidly increases while the loss factor tan δ decreases at around 32 oC corresponding to the volume-phase transition temperature of PNIPAAM. Mechanical properties of NC-DNA hydrogels were investigated at 24 ± 1 °C by uniaxial elongation and compression tests. Because of the significant effect of the heating-cooling cycle between below and above the denaturation or the melting temperature (Tm) of ds-DNA on the hydrogel properties, the tests were carried out on the gel specimens before and after subjecting to the thermal cycles. As it is expected, a significant increase in Young's modulus and fracture stress was observed after the thermal cycle. Moreover, the stretchability of NC-DNA hydrogels is between 140 and 800% at or above 4 w/v % DNA, whereas it significantly increases with decreasing DNA content. Highly stretchable hydrogels exhibiting an elongation at break between 1100 and 1500% could be obtained at 1-4 w/v % DNA. Similar results were also obtained from uniaxial compression tests in which the same heating-cooling procedure was applied while this behavior is independent of the Laponite concentration. The quasi-reversible manner of dissociation of hydrogen bonds in NC-DNA hydrogels under stress suggests their self-healing abilities. When the two gel samples were put into contact and allowed to stand at 90 °C for 30 min followed by slowly cooling to room temperature, it was not possible to separate the two parts by stretching manually. It is interesting to note that both the Young's modulus E and the fracture stress σf of the hydrogel significantly increase after its healing at 90 °C. Enchanced mechanical properties after self-healing of NC-DNA hydrogels healed at 90 °C is due to the increase of the modulus E and fracture stress σf of DNA-containing hydrogels as observed during the heating-cooling cycles. This increment of mechanical properties as well as the self-healing behavior was not observed for the gel samples with or without DNA when the gels are healed at temperatures below 90 oC, suggesting that DNA itself faciliating the healing process by formation of bridges between the cut surfaces via the H bonds. Swelling profile of NC-DNA hydrogels also suggests that ds-DNA in the hydrogels partially releases during the initial swelling process. Thus, the hydrogel initially behaves as a polyelectrolyte, due to the osmotic pressure of phosphate counterions of DNA and attains a large swelling ratio. However, as the DNA is gradually released from the hydrogel, the ionic osmotic pressure reduces so that the hydrogel progressively changes into a less ionic hydrogel with a distinctly reduced swelling ratio. Increasing equilibrium swelling ratio mrel,eq with increasing DNA content indicates that a larger amount of DNA can be entrapped within the gel network in equilibrium with water as the DNA concentration at the gel preparation is increased. This DNA release behavior during swelling process may provide applications of NC-DNA hydrogels as DNA carriers in gene therapy methods.
Influence of powder and emulsion polymer addition on strength and capillary properties of cement mortars
Mortars are mixtures of sand, cement, and water; the addition of a coarse aggregate converts a mortar into a concrete. The mortars are construction materials that are used for both plastering of buildings and aimed to binding of wall materials such as stone and brick. Mortars can also be used as a protecting layer over the casted concretes. Furthermore, mortars can be considered as a kind of concrete without coarse aggregate; for this reason, the experiments made on the mortars can also be used for prediction of concrete properties. Concrete is one of the most broadly used construction materials and it is the second the most consumed material in the World following the water. Concrete is used both in water constructions such as dams, canals, bridges and also in roads, buildings and other structures. Concrete, by inserting steel bars in it, forms reinforced concrete and it is the main load carrying part of the structures. Due to its good fire resistance, high level of waterproofing and good sound insulation, it is preferred material in the structures. Choosing the proper mixing proportions provides balanced properties such as economy, easy processability, waterproofing, strength, durability and appearance. Good quality concrete can be obtained easily when suitable sand and coarse aggregate (gravel or coarse crushed stone) are found. Studies have been carried out for years to develop the various features of concrete. Just as the basic materials proportions of the mortars, such as water-cement, sand-cement ratio can be changed; also these properties can be improved by emulsion, latex, plasticizer and superplasticizer, polymer-based admixtures, and also by mineral-based admixtures, such as, fly ash, blast furnace slag and silica fume. Polymer concrete, is a mixture of cement, polymer, aggregate and water, in which cement is used as a binder. Polymer modified mortar and plaster systems are product groups that removes the properties such as shrinkage which can be seen in cement based system, water bleeding, slow and quick initial setting on different thermal environments. They separate from conventional materials with some better properties such as water retention, high level adhesion performance, and waterproofing Furthermore; they can be longevity thanks to its high water proofing features. Emulsion or latex type polymer additives in mortars forms a second binding phase in addition to cement. It make possible to reaching the high physical mechanical strength of concrete by film formation in internal structure of mortar. Some polymers can be improve the workability through act as a superplasticizer and improving the flowing rate of mortars. Polymer added mortars are not only used to provide mechanical performance but also used to decrease the maintenance cost during usage and application. These properties of polymers and modification ability of polymer additives in mortars constitutes the basis on the subject of this study. It was studied to observe how the properties of mortars are changed with different mixing parameters and by by using polymer additives in mortars. The polymers were provided by Organik Kimya Inc. and Vinyl acetate-vinyl versatate copolymer was used as the powder polymer, and acrylic emulsion polymer was used as the emulsion polymer. The VA / VeoVa copolymer is an inverse chain polymer having hydrophobic hydrocarbon groups. This provides a low surface tension and a hydrophobic structure to the monomers. This hydrophobic structure makes it possible to use it as construction materials. Furthermore, The VA / VeoVa copolymers are not degrade under UV light. The studies show that VA / VeoVa polymer has good effects on physical and mechanical properties of cement mortars, reduces the shrinkage ratio and improve the hydrophobicity and waterproofing of cement mortar. Acrylic emulsion polymers are generally used in the paint and coating industry. Acrylic esters and methacrylic esters have quite different properties. The amount of these esters in the polymer, indicates the material properties, rigidity, flexibility, chemical resistance and leveling during film formation. Because of these features; these polymers can be used in textiles, adhesives, printing inks, paper coatings and construction sectors. Furthermore, because of water-cement ratio is one of the most important strength parameters for mortars and concrete, the studies were made based on this criteria. There is a need for water to the hydration reaction of cement. Hydration products causes the increasing of the mechanical properties by binding the aggregate particles (sand and coarse aggregates). However, if more water is used than the necessary amount for the hydration of cement, the extra water is get evaporated by the time leaving voids behind. These voids lower the mechanical strength of the concrete. How much porous structure exists in the concrete, it means the less strength and high permeability it has. The water content in the mortar greatly effects the formation of porous structures. Therefore, one of the parameters in this study investigated is the water-cement ratio. In this thesis, productions were made for both polymers at the polymer-cement ratios of %0, 5%, 10%, 15% and at the water-cement ratios of 50%, 55%, 60%, respectively. During the production, reference samples were prepared in the first phase and subjected to water and air curing. For cement-polymer composites curing conditions after production are important. There is needed both water and air curing. Because the cement in the mortar is needed water curing for hydration reaction and also needed to air curing for polymer additive to form a film in the mortar structure. For this reason, the cement-polymer composites were exposed to firstly water cure for 3 days followed by 56 days of air cure. At the end of 56 days, mechanical tests were done on the specimens. During the preparing of fresh mortars, it was subjected to flow (slump) test and test result took into account in productions. Slump test gives an idea about the workability, consistency and viscosity of mortar. Besides, in order to calculate the air content, the unit weights were determined after each production. As the water-cement ratio increases, it was observed that the percentage of flow-slump increases and therefore the workability of the mortar increases. As well as, it was understood that as the polymer-cement ratio increased, the air content decreased and the porous structure was prevented. But; it was seen that the air content percentage decreased moreover as the polymer-cement ratio increased. In this thesis, the tests were made in accordance with ASTM C-1439 and TS EN 196-1 standards. For the hardened state tests 40x40x160 mm³ molds were used. Specimens were removed from the molds 24 hours after the casting and the curing program is applied. It is expected that the rate of water holding property will be high when producing polymer added concrete. To measure this, water retention test was made for both reference samples and polymeric mortars. Water retention is important feature and effects the workability and the adherence between mortar and brick. How much water retention feature of concrete if there is, the less of feature of porous structure in it. DIN 18555 standard was used for water retention test; according to this test result, water retention percentage of polymeric mortars tends to increase as the polymer ratio increases. Also, it has been observed that the emulsion polymer has more water retention feature in comparison with the powder polymer. On the other hand; after the curing program, to measure the mechanical properties, flexural (bending) and compression, for impermeability properties, capillarity and water absorption tests were done on the samples. Firstly, the bending strength tests were done on three specimens for each mixture, and a total of 6 pieces were formed as a result of the flexural strength test. Compression and capillary tests were done on the specimens that were obtained from flexural test. According to flexural strength test; it was observed that both polymer additives (both emulsion and powder polymers) increased the flexural strength. The reason for this increasing in flexural strength is interpreted as, concrete internal structure is strengthened by the polymer film layer. Besides; according to the results of compression strength test; it was observed that the polymer addition into mortars reduced the compressive strength. The reason of this can be due to the soft-tissue polymer additive formed in the mortar that showing similar behavior to the air gaps in the concrete, reducing the compressive strength. Before the capillary tests were done, the specimens were kept in oven at 55°C temperature for 48 hours. After removed from the oven and cooled, only the surface of 40x40 mm part was contact with water and the side surfaces were paraffinized in 10 mm height from the bottom. Capillary test for 64 minutes was performed. After the capillary test, water absorption test for 48 hours was performed on the specimes. From each capillary water absorption test capillary coefficients were calculated from the plots of water absorption through unit area versus time. In order to see the effect of polymer addition on the capillary test; capillary was plotted with respect to P/C ratios. According to these results, polymer admixtures have a positive effect on capillary and water absorption, besides powder polymer has better capillarity properties than emulsion polymer. Although the polymer was added to the mortars, the reason of difference in emulsion and powder polymer result may be the effect of different polymer admixtures on the hydrate morphology and hydration kinetics. On the other hand, it was observed that capillary water absorption and water absorption of mortars which has lower W / C ratio for both powder polymer and emulsion polymer, were found to be lower. The reason for this can be attributed to the increased void contents, which increases the permeability, as the water / cement ratio increases.
Synthesis and sensor appplication of reusable fluorescent uranyl-imprinted polymer gels
The sol-gel process, also called as chemical solution deposition, is a technique at room temperature commonly used in ceramic engineering and materials science such as electronics, nanotechnology, optics, medicine etc. In generally, sol-gel describes the synthesis and processing of ceramic and glasses. In addition the sol-gel process, also referred to as the "chimie douce", is based on the preparation of a solid solution of solids at lower temperatures than conventional preparation methods, using either a left or gel medium step. This is a simple technology in theory but in practice, it requires a significant amount of effort. Many scientists have experienced about this phenomenon for many years. Thanks to this process (stability, optical transparency, chemical) porosity and chemical resistance, etc.), homogeneous inorganic oxide materials can be obtained at room temperature without the need for the high melting temperature required for conversion to inorganic glasses. The ability of the sol- gel process to be achieved under extreme moderate conditions (often at room temperature) and the availability of products in various shapes, sizes and formats has allowed this technology to become increasingly used in various scientific and engineering fields. In general, sol-gel chemistry, hydrolysis and condensation reactions, oxide are based on the transformation of molecular network precursors in the network. Alkoxide groups in the alcohol-water solution are gradually removed by hydrolysis in the presence of basic or acidic catalyst and hydroxyl- groups. Gelling occurs when the growing polymer networks come together to form a network covering the entire solution volume. At this point of gelation, both the viscosity and the elastic modulus rise steadily. The gel can be dried by evaporation to form xerogels, or by supercritical fluid extraction to obtain aerogels. The hydrolysis and condensation reactions depends on many different parameters such as pH, temperature, solvent, the kind of catalyst, nature and concentration of the initiator, the type of solvent and the acidity of the medium, type and concentration of additives, aging time of the mixture, component concentration in the initial mixture and ratio of the alkoxy with respect to water. One of the most important aspects of sol-gel science is molecular imprint polymers. Molecular Imprint Technology (MIT) is a synthetic approach to designing powerful molecular recognition materials that can mimic natural recognition agents such as antibodies and biological receptors. Although the origin of molecular imprint polymers is based on the early 1930s, the interest of researchers has only attracted attention in the 1970s, and since 1970, the interest in this field has been increasing and has become an important and active research area in recent years. These polymers are seen as versatile and future bright polymers capable of recognizing both biological and chemical molecules, including amino acids, proteins, nucleotide derivatives, drugs and foods. Because of the unique properties of MIPs, they are used in different applications such as separation, purification, sensor and biosensor construction and drug delivery. As can be seen from many recent articles published in recent years, chemical sensors and biosensors are receiving increasing attention in the field of modern analytical chemistry. This increase in the number of studies is mainly due to the growing demand in basic fields such as medicine, food and the environment. The identification and removal of toxic and radioactive heavy metals is very important because of their biological, environmental and industrial effects. The development of selective and differential chemosensors for the determination of toxic heavy metal ions is of interest and this interest is increasing. Uranium is a radioactive and toxic element that occurs in the environment as a result of many processes such as nuclear power generation, construction of nuclear weapons, processing and destruction of nuclear waste, nuclear accidents and burning of fossil fuels. Nuclear fuel production causes pollution in water and soil. Under environmental conditions, the uranyl ion in water forms in hexagonal form, moving on the earth around uranium, nuclear waste zones and processing facilities. The human body may be exposed to airborne dust, or to uranium-contaminated food and water. Although soluble uranium compounds can be rapidly extirpated during the digestion process, they are confused with the bloodstream, especially by the ingestion of powders into the lungs, creating a serious hazard for human health. Uranium detection is crucial for applications related to nuclear work such as monitoring environmental cleanliness, producing and reprocessing fuel. One uranium species of interest, uranyl ion, has accumulated over many years in the bone, liver, kidney and reproductive tissues. For this reason, the monitoring of the small amount of uranium in the forest is an important issue. Numerous methods are used to determine uranium. However, these methods require limited capacity and high operating costs. In this study, four different kinds of polymeric materials were synthesized, two of which were obtained as fluorescent sol-gel particles and two of which were obtained as fluorescent stimuli-responsive hydrogels. In the first part of study, the fluorescent functional precursor (QP) was synthesized by the reaction between 3-aminoquinoline and 3-isocyanatopropyltrimethoxysilane, and then the sol-gel material was synthesized by using QP as fluorescent probe, TMOS as cross-linker and TEA as catalyst in the presence of uranyl ion. The obtained sol-gel particles in powder form was designated as U-imp1 and the sol-gel particles which was synthesized in the absence of uranyl ion was designated as N-imp1. The characterizations of both sol-gel particles were made by FT-IR, BET analysis, optic microscopy, SEM and TGA. The optimum solution conditions such as composition of solvent mixture and pH for the determination of uranyl ions by using both N-imp1 and U-imp1 hydrogels were investigated and compared by fluorescence emission exhibited by the particles in solution. In the second part of the study, fluorescent non-imprinted (N-imp2) and uranyl ion-imprinted (U-imp2) hydrogels were synthesized and characterized. U-imp2 hydrogel was prepared in dioxane by free radical polymerization of N-isopropyl acrylamide as a main component, methacrylic acid as a functional monomer, 9-vinylcarbazole as a fluorescent monomer and N,N-methylenebis acrylamide as a cross-linker in the presence of uranyl ion. Imprinted hydrogel, which was prepared in the presence of uranyl ion, contains negatively charged monomer units to interact with positively charged uranyl ion. Upon interaction with uranyl ion, fluorescent gel exhibits a change in fluorescence intensity. As uranyl ion concentration increases in solution, the quenching of fluorescence of imprinted polymer increases. When compared with N-imp2 hydrogel that was prepared in the absence of uranyl ion, the amplified fluorescence quenching was observed in the case of imprinted hydrogel, showing that certain cavity was created for selective binding of uranyl ion. Swelling behavior of polyelectrolyte hydrogel was also investigated in solvent mixture and collapsing behavior of the hydrogels was evaluated depending on temperature. Furthermore, swelling kinetic of stimuli-responsive hydrogel was investigated in ethanol-water mixtures with different composition. The sensor behavior of fluorescent hydrogels for the determination of uranyl ion was evaluated both in swollen and shrunken state by monitoring of the fluorescence intensity of the carbazole moiety in hydrogels.
Üretim parametrelerinin sürekli grafen lif özellikleri üzerine etkisi
Graphene is carbon-based material that has promising properties for different applications in energy, catalysts, radar absorber, sensor, etc. Due to its fascinating facilities, this material has been studied by many researchers. By these knowledges, continuous graphene fibres have been fabricated by wet-spinning method and co-coagulants processes have been employed respectively. Because of the excellent properties such as mechanical, thermal, chemical, electrical and economical properties it can be used for low cost production, easy processing with high yield. Graphene (G) is the material which is type of graphite with single layer. Visual properties of G is different from other carbon based materials. It has a 2-dimensional (2D) honeycomb structure and has sp2- bonded carbon atoms in its structure. There are several methods to obtain graphene. It can be directly obtained from graphite or may be obtained from reduction of graphene oxide (GO). Graphene oxide is obtained by the oxidation of graphite by different methods such as Brodie, Hummers or Staudenmaier. Among these, the most common method is Hummers method. The exfoliated GO sheets are highly oxidized and featured with the residual epoxides, hydroxides and carboxylic acid groups on their surfaces. This study reports the effect of processing parameters such as time, temperature of the exfoliation together with dispersion preparation methods of graphene oxide on the properties of continuous graphene oxide fibers produced by coagulation bath. Relationship between changing parameters and structural properties of graphene oxide fiber, fiber morphology, roughness, crystalline structure have been discussed. Higher exfoliation time leads to an increase in Tex count of fiber, while longer ultrasonic times resulted in lower tex count compared to both shorter ultrasound time and mechanical homogenization. Shorter ultrasonication period and shorter exfoliation time leads to higher electrical conductivity compared to mechanical homogenization. Shorter ultrasonication period results in slight tendency of an increase in breaking strength. Besides, the effect of exfoliation time and presence of activated carbon particle (AC) on graphene oxide fiber's properties has been analyzed. It has been seen that cross-sectional appearance of sample with AC is grating and rough because of AC. The addition of AC did not change the electrical conductivity. However, AC results in an enormous decrease in the mechanical properties. In the light of this study, optimal conditions for producing continuous graphene oxide fibers can be determined. This study can take an important role for further researches.
Mikro gözenekli polipropilen nefes alabilen film üretimi
Polymeric structures that pass water vapor and air, but exhibit barrier properties against liquids are called breathable films. Breathable films, that find new uses in the direction of evolving and changing living standards, can be grouped under two main types; monolithic and microporous. In addition to monolithic structures that inherently breathe, microporous structures are obtained by the addition of inorganic fillers to the polyolefin matrix. Stretching this filler loaded polyolefin matrix creates the micro pores and achives the breathability. Microporous breathable films potentially capable of creating new markets because of their low cost and usefulness. They are widely used in many industries, especially hygienic products (baby diapers, single wraps, patient gowns), construction materials (roof insulation, wall insulation) and personal protective clothing. A standard microporous polyolefin, - generally polyethylene-, mineral filler breathable film contains billions of micropores. The mineral fillers are active ingredients which give the film unique features enabling it to breathe through the network of micropores. The hydrophobic nature of the filler is a desirable feature as it will reduce water retention during production processes. Examples of the inorganic filler include calcium carbonate, talc, clay, kaolin, silica, magnesium carbonate, magnesium sulfate, calcium sulfate, aluminum hydroxide, zinc oxide, zeolite. The filling rate to the polyolefin matrix usually varies between 10-70%. Breathable films are used in backsheets, for example as a backsheet component laminated to a nonwoven and/or other layers. They are used in many of today's personal care absorbent articles. Filled and stretched polyolefin films are making the diapers more comfortable to the wearer since they provide good water vapor transmission. With the using laminates of breathable films and nonwoven webs, the relative humidity and temperature within the personal care products can be reduced. The breathable films themselves provide vapor breathability and liquid barrier, but are typically not strong enough to be used alone. The nonwoven webs provide strength as well as fabric-like properties to the laminates. To making a polymeric film vapor permeable, includes mixing a matrix polymer with the inorganic filler via double-screw compound extrusion process. The resulting mixture is using to produce monolayer or multilayer film via cast or blown extrusion process. Then, the film is heated and stretched, causing voids to form in the areas surrounding the filler particles via stretching unit. The aim of this thesis is to use polypropylene matrix instead of the classicized polyethylene matrix used in the production of microporous breathable films. As the inorganic filler, surface-modified calcium carbonate is preferred. The use of polypropylene matrix in microporous film will ensure a more consistent structure since used laminates are generally made from polypropylene. This compliant construction is expected to reduce the use of glue and improve process difficulty such as reduce the differences of melting point of films and laminates in the lamination process. Moreover, it is one of today's needs to obtain films with high strength that will not be laminated and used as a single layer. In the first step of the thesis study, polypropylene based two different compounds that contained 50% (C1) and 60% (C2) of surface modified calcium carbonate were prepared in a twin screw extruder. The motor speed was 600 rpm during the compounding process and the reverse temperature profile was prefered. In the second stage, the experimental design was planned for the samples obtained by the blown film extrusion method and the variable parameters were determined. In terms of experimental design, weight, width, and stretching ratio were accepted as constant parameters. The ratio of linear low density polyethylene to be used during the blown film extrusion process and the two prepared compounds (C1 and C2) were determined as variable parameters. In this direction, it was planned to obtain four film samples (BF1, BF2, BF3 and BF4) with 0% and 15% of linear low density polyethylene added to C1 and C2 compounds. At the last stage, the micropores were obtained by using the stretching unit to achive breathability. MDO (Machine Direction Orientation) unit was used as the stretching unit with the 1:4 stretching ratio. Temperatures of the preheating, stretching, annealing and cooling rollers in the MDO unit were determined in terms of material structure and kept constant throughout production. In the study, a commercial polypropylene and polyethylene based compounds were characterized and compared with the prepared compounds, C1 and C2. The DSC, FTIR and ash analysis were investigated according to the material structure of the compounds. Increasing the amount of calcium carbonate in the compound has been found to increase the melt flow rate and density. Linear low density polyethylene can be added to improve the processability of the polypropylene based compounds. The obtained film samples were analyzed with the DSC, FTIR, ash tester, melt flow rate tester and density tester. The thermal characteristics and the IR absorption peaks of the film samples were determined. As a result of the ash analysis, the ratio of inorganic filler in the film matrix, namely calcium carbonate, was determined. The effect of the ratio of calcium carbonate contained in the film samples on the melt flow rate and density values was observed by analysis. A polyethylene based commercial microporous film was analyzed comparatively with BF1, BF2 and BF4 film samples for mechanical properties such as tensile strength at break, tensile strength, elastic modulus and tear strength. As the polypropylene is more rigid, it has been found that the tensile strengths and elastic modulus of the film samples are higher than commercial microporous polyethylene breathable film sample. Tensile elongation at break of the film samples are lower than commercial microporous polyethylene breathable film sample. It has been found that the tear strength values are rather low compared to the commercial microporous polyethylene breathable film sample. When the obtained film samples are compared within themselves, it is seen that the strength values change with the calcium carbonate ratio in the film matrix. Increase in the amount of calcium carbonate results in a decrease in strength values. The breathability (water vapor permeability), one of the most important parameters, was evaluated comparatively by using the MOCON analysis method. The water vapor permeability can be basically related to the material structure, the amount of calcium carbonate and the rate of stretching in the stretching unit. When the obtained film samples are compared within itself, it was found that water vapor permeability was proportional to the calcium carbonate ratio in the film matrix. BF1 and BF4 film specimens are particularly acceptable when compared with the commercial microporous polyethylene breathable film sample in terms of water vapor permeability. Within the scope of the thesis study, it is aimed to obtain micropores. For this reason, by using SEM analysis, surface morphology of the obtained film samples was examined and random micropores were observed at different sizes. It has been determined that the size of the micro pores in the vertical level is higher than the horizontal level. This is due to the fact that the vertical level exposed to more stress. It was seen that the stretching direction is vertical. The resulting microporous polypropylene breathable films can be used in the hygiene sector in terms of water vapor permeability values. More rigid materials were obtained compared to polyethylene based microporous film. It is known that the nature of the polypropylene structure is coming from the propylene monomers is more rigid than the polyethylene.
Preparation of cross-linked poly (styrene) based resin amidated by staudinger reaction, modification with iminopropylene glycole and removal of the boron from aqueous solutions
Boron is the fifth lightest element in the periodic table and just one place before carbon. It is the only non-metallic element of group III. Although boron is broadly dispersed in geosphere, it is found as low concentration. Boron salts and boric acid are widely used in industry production of porcelain, glass, carpets, cosmetics, fire-retardant fabrics, weather proofing wood and photographic chemicals. Moreover, boron is a crucial element for system of living organism. However, excessive boron has drawback effects on humans, animals and plants. To keep it up healthy levels, the World Health Organization (WHO) has set a boundary of 2.4 mg/L of boron in potable water. Subsequently, removal of boron from wastewater is crucial issue. Removing of boron from wastewaters and waters has no simple procedures. There are numerous method for the removal of boron that are precipitation-coagulation, adsorption on active carbon or polymeric resins, cellulose or clay minerals, solvent extraction, use of boron selective resins, membrane filtration, ion exchange with basic exchanger and adsorption on oxides. Adsorption as a removing of boron compound from water sources is the best in terms of low cost, effective and easily applicable method when it is compared with the other methods. To begin with part of this study, cross-linked poly (vinyl benzyl chloride) (PVBC) resin was prepared by suspension polymerization. PVBC was modified with sodium azide. Then, amination of the resin was provided by Staudinger reaction. The last part of preparation of boron selective resin is modification of aminated resin with glycidole. The resin was characterized thanks to Fourier-transform infrared spectroscopy (FTIR) in order to understand importance of functional groups for boron selectivity. Total amine content of was determined as 3.75 mmol/g sorbent. In the second part of this study, boron sorption experiments were carried with modified resin. Effect of different boron concentration was researched for the resin. Maximum boron loading capacity of the IPG-resin was found 3.727 mmol per gram sorbent. Moreover, effect of salt and foreign ion such as Ca+2 and Mg+2 on boron sorption capacity was investigated. In addition, capacities of boron sorption were considered with varying pH value between 2.0-8-0. The last of part of this study, sorption isotherm models that Freundlich, Langmuir and Tempkin, were examined for maximum sorption capacity of resin. Furthermore, kinetics of boron sorption was studied with the similar concentration of seawater. Pseudo first order, pseudo second order and intra-particular diffusion kinetics models were applied in order to understand of efficiency of the resin. Besides, regeneration of the resin was examined. Amount of boric acid, which was recovered of the loaded resin, is 3.57 mmol/g. It was indicated that the resin has ability of desorption almost entirely.
Electrospun nanofibers from copolymers and terpolymers of acrylonitrile, vinyl acetate and vinylphosphonic acid
Polymer materials are active in every area of human life. They are preferred because they are lighter than ceramics and metals and are easy to process and have high mechanical properties. Depending on the area to be used, a number of improvements can be made using physical or chemical methods to improve the properties of polymer materials. Particularly fillers and additives are frequently used with the aim of enhancing the polymer properties. The structure of each filler and additive to be used varies depending on the polymer structure. Additives such as flame retardants, stabilizers, antioxidants and plasticizers are frequently used to improve the properties of the materials. Nanofibers are found in many applications as high function materials with diameters below 100 nm, high surface area and porosity. These applications include areas such as scaffolds in tissue engineering, drug delivery, enzyme immobilization, filtration, wound healing, biosensors. Acrylic fibers are the most commonly used fiber type in the textile industry. Acrylic fibers found in the works to meet the increasing wool need in the world are preferred because of their natural feel like wool, easy washability, resistance to sunlight and chemical resistance. The first acrylic fiber produced as homopolymer with 100% acrylonitrile polymerization, marketed by Orlon patent name, is hard and brittle and difficult to paint. In order to solve this difficulty, it was mixed with a second monomer and converted into copolymers to make the use in textile. Acrylic fiber, which is made up of acrylonitrile monomer and comonomer, usually produced by wet and dry spinning systems, can be produced as a nanofiber. In this study, it is aimed to produce nanofibers of acrylonitrile copolymers and terpolymers. For this purpose, the polymerization reaction of acrylonitrile monomers and comonomers was carried out and the nanofiber production was carried out using electrospinning technique. At the same time, acrylonitrile copolymers and terpolymers were produced in different formulations with different water/monomer ratios and nanofiber of each formulation was produced. In the first step, the acrylonitrile monomer and the vinyl acetate comonomer are polymerized with an ammonium persulfate initiator at a temperature of 70 °C. Copolymers have been produced in different compositions with the water/monomer ratios: 3,5 and 10. The same method was used for the terpolymer production. In addition to acrylonitrile and vinyl acetate monomer, vinylphosphonic acid monomer is used for the terpolymer. Environmentally friendly, halogen-free flame retardant species, phosphorus-containing flame retardants are widely used. In the condensed phase mechanism, flame retardant phosphoric acid contributes to the formation of coal by altering the thermal degradation of the polymer. In the second step, solutions were prepared from the polymers formed using dimethylformamide (DMF) solvent. While the copolymer solutions were prepared at 10%, the terpolymer solutions were prepared at 5%. These solutions were produced to use in electrospinning method which is a nanofiber production method. Nanofibers and polymers are characterized by FTIR-ATR (Fourier Transform Infrared Spectrophotometer), SEM (Scanning Electron Microscope), TGA (Temperature Mass Analyzer), DSC (Differential Scanning Calorimetry), Ostwald viscometer, ICP (Inductively Coupled Plasma) analysis. Nanofiber formation was carried out from copolymer solutions prepared with different water / monomer ratios. In the case of the terpolymer solutions prepared at the same ratios, the nanofiber formation of the terpolymer solution having a water / monomer ratio of 10 can be carried out, whereas the nanofiber formation of the terpolymer solutions having a water / monomer ratio of 3 and 5 can not be achieved. This is due to the high viscosity values of the terpolymer solutions with a water / monomer ratio of 3 and 5. These polymers with a high viscosity values appear to release solvent when fiber production is needed, during the fiber production stage. It is known that glass transition temperatures and melting temperatures of semicrystalline polymers decrease with comonomer addition. The results of differential scanning calorimetry (DSC) show that the glass transition temperatures of the terpolymer and copolymers are increased when compared to the glass transition temperature of the acrylonitrile homopolymer. The increase in glass transition temperatures is due to the influence of the hydrogen bond formed by the electronegative atoms in the vinyl acetate monomer and the vinylphosphonic acid monomer. In addition, the increase in glass transition temperatures of terpolymers is greater than that of the copolymers. The Char layer enhances the formation of water vapor which reduces flammable volatile substances. At the same time, it reduces heat transfer from the heat source to the polymeric material. The increase in the amount of residues in the polymer means that the formation of carbon layer is increased. In the sample CP-2 with a residual amount of about 52%, the most carbon layer formation occurs. Among the terpolymers, TP-1 with a residual amount of 47% shows the maximum amount of residues and maximum carbon layer formation. In addition, carbon layer formation in the terpolymers decrease with increasing the amount of water. It has been found that the contribution of the synthesized copolymers and terpolymers to carbon layer formation is less than the contribution of homopolymer and commercial P (AN-co-VAc) to the formation of carbon layer. According to the water absorption test results, it appears that the water absorption percentage of the synthesized copolymers and terpolymer increases with respect to homopolymer. If we compare the water absorption percentages of the copolymers and terpolymers, it is seen that the water absorption percentages of the copolymers are almost equal to or even greater than the terpolymers. The reason for this is that the phosphonic acid groups present in the terpolymers form hydrogen bonds between themselves and therefore the rate of hydrogen bonding with water is reduced. Low water absorption values of terpolymers may be useful for use in different areas of nanofibers. These polymers can be used to produce a water-resistant nanofiber.
Design and synthesis of molecularly imprinted stimuli-responsive hybrid sol-gels for sustained release of donepezil
Inorganic sol-gel-derived materials had been investigated and commercialized a few decades ago and due to the profound understanding of the underlying chemical and technical processes are still present as important examples of large-scale applications of the sol-gel technology. The growing interest in sol-gel science is due to the straightforwardness in tailoring the porosity in these materials, particularly in achieving molecular recognition in different systems such as adsorption or absorption, stationary phases in liquid or gas chromatography and chemical sensing applications. The production of sol-gel materials provides numerous advantages over the other conventional synthetic schemes. One of the major advantages is that these systems allow the manufacturing at low temperatures, which enables us to generate functionalized matrices, where others lack this ability. These materials are synthesized from solutions that help us to generate thin films and bulk products of desired shape. In this process, the chemical compositions of the starting material controls porosity by carefully monitoring the reaction parameters. The thin sol-gel films can easily be immobilized on glass and other silicon substrates through covalent linkage, which is an additional feature of these materials. The end product material can be configured in different forms like powder or dispersion forms, thin films, fibers and monoliths, etc. One of the most exciting achievements of this technique is that a hybrid material of organic and inorganic substances can be synthesized. To a certain extent, these hybrid materials combine the most important properties of their constituents, like high transparency, low processing temperatures, sufficient thermal stability and are easily accessible because of an unique availability of the respective precursors (commercially available metal alkoxides and organo (alkoxy)silanes as well as nanoparticles). The sol-gel process, as the name implies, involves transition from a liquid 'sol' (colloidal solution) into a 'gel' phase. Usually inorganic metal salts or metal organic compounds such as metal alkoxide are used as precursors. A colloidal suspension or a 'sol' is formed after a series of hydrolysis and condensation reaction of the precursors. Then the sol particles condense into a continuous liquid phase (gel). With further drying and heat treatment, the 'gel' is converted into dense ceramic or glass materials. Generally three reactions are used to describe the sol-gel process: hydrolysis, alcohol condensation and water condensation. Because water and alkoxides are immiscible, alcohol is commonly used as co-solvent. Many sol-gels that are used for biomedical purposes should be biocompatible and often biodegradable. This also makes them ideal candidates for a controlled drug release. Sol-gels have a porous network. Often we can control the porosity of sol-gels by controlling the density of cross-links or by changing the swell affinity of sol-gels in the environment. This porosity property of sol-gels helps the release of drugs from sol-gels. The release of drug from sol-gels can be controlled by controlling the diffusion coefficient of drugs through sol-gel matrix. We can also make a depot formulation of hydrogel-drug. The depot formulation can be made by trapping drugs into liposomes and incorporating liposomes in the hydrogel. Controlled release drug delivery system works on many different mechanisms to controlled release. Donepezil hydrochloride (DP) is a drug administered for Alzheimer's disease (AD) treatment, and it is a potential template molecule for imprinted hybrid sol-gels. AD is the most common type of dementia clinically characterized by progressive loss of memory and deficits in different cognitive domains. The nature of AD limits the effectiveness of available oral treatments. The most of drugs for AD are commercially available as oral formulations. However, due to a multitude of risk factors in the AD population, such as memory loss and high incidence of dysphagia, oral formulations has been poor. Since DP also causes gastrointestinal adverse effects, a transdermal delivery system might be a suitable method to overcome the problems of conventional oral administration of DP. Ideal drug delivery system has to be inert, biocompatible, mechanically strong, comfortable for the patient, capable of achieving high drug loading, readily processable, safe from accidental release, simple to administer and remove, easy to fabricate and sterilize, free of leachable impurities. These criteria can be obtained by molecularly imprinted sol-gel materials, which are the best candidate to design an artificial drug model for controlled drug release. Interest in stimuli-responsive polymers is steadily gaining increasing momentum especially in the fields of controlled and self-regulated drug delivery. Stimuli-responsive or smart polymers are macromolecules that display a significant physiochemical change in response to small changes in their environment such as temperature, pH, light, magnetic field, ionic factors, etc. In this study, the release of Alzheimer's drug DP from two kinds of hybrid sol-gels, which were prepared from newly synthesized precursors, was investigated. We prepared silanated O,O′-Bis(2-aminopropyl)polypropylene glycol (JD400) and O,O′-Bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol(JED600) by coupling 3-isocyanatopropyl-triethoxysilane (ICPTS) with the amine end groups of both glycols through urethane bonds. Hence, trimethoxysilane terminated O,O′-Bis(2-aminopropyl)polypropylene glycol (coded as JD400-ICPTS) and O,O′-Bis(2-aminopropyl) polypropylene glycol-block-polyethylene glycol-block-polypropylene glycol (coded as JED600-ICPTS) were synthesized. The purified silicon-containing trifunctional monomers were identified using Attenuated Total Reflectance-Infrared (ATR-FTIR). The Donepezil hydrochloride (DP) imprinted hybrid sol-gels were prepared by using the following components: DP as a template; precursors, JD400-ICPTS and JED600-ICPTS as spacers; Aminopropyl-trimethoxysilane (APTES) as a functional monomer interacting with DP; citric acid as an acidic catalyst. The imprinted hybrid sol-gels were prepared in the presence of DP molecule using each JD400-ICPTS and JED600-ICPTS precursors, APTES and citric acid. Then, the as-prepared pre-gel solution was poured into the teflon mould and was allowed to hydrolyze. The gels with film form were obtained and kept under vacuum at 40 oC for the completion of condensation reaction. Hybrid sol-gels are indicated as JD400 gel and JED600 gel. Non-imprint hybrid sol-gels were prepared in the absence of DP at the same conditions with similar to imprinted hybrid gels. Gelation time for the formation of hybrid sol-gel network was obtained by observing the viscosity change in pre-gel solution with or without DP. Swelling degree of hybrid sol-gel films were elucidated by obtaining data depending on time in ethanol-water mixtures with different compositions at temperatures of 25 oC and 37 oC. For each of the hybrid gels, DP release in ethanol-water mixtures at 25 oC and 37 oC and, also in buffer solution with different pH values was evaluated by using the calibration curves of DP. Calibration curves of DP were obtained for each described solutions by recording the absorption spectra of DP and collecting the absorbance values of DP at 315 nm depending on concentration and, then DP released by different hybrid sol-gels was calculated. Fractional release of DP at initial of time interval and equilibrium amount from JD400 gel and JED600 gel were evaluated. The time-dependent swelling behavior of the hybrid sol-gel films and DP release characters of each hybrid gels depending on composition of water-ethanol, pH and temperature of solution compared. DP release kinetics of hybrid sol-gels and mechanism at temperatures of 25 oC and 37 oC were determined by fitting the release data to Korsmeyer-Peppas kinetic model.
Emulsion polymerization of vinyl acetate by urethane based surfactant and high solid content water-based emulsion polymerization of acrylic monomers
Emulsifiers, another name are surfactants, are characterized by a chemical structure comprising a hydrophilic group having one and/or two hydrophobic flexible alkyl chains of a certain length. In small quantities dispersed in the aqueous phase, the surfactant is adequate for self-assembly into the micelle micro aggregates. Surfactants are used in several areas for different purpose such as painting, emulsion polymerizations, adhesives, textile industry, etc. Surfactants are divided into four main categories. They are anionic, cationic, non-ionic and zwitterionic. In this study, a new nonionic polymeric surfactant (PU) has been synthesized with the reaction between Poly(ethylene glycol) dimethyl ether (PEG500) and Toluene 2,4-diisocyanate (TDI). The polymeric surfactant was characterized by using FT-IR spectroscopy, GPC, critical micelle measurements via tensiometer. Critical micelle concentration of PU was determined by surface tension measurements. This value was calculated as 0.68x10 mg / mL. Molecular weight of the PU was determined by gel permeation chromotography (GPC). Mw, Mn and Mz molecular weight was measured as respectively 1361, 1163 and 1524 g / moles. Polydispersity index was obtained as 1.171 . PU was used emulsion polymerization of vinyl acetate and copolymerization of metyl methacrylate and butyl acrylate depending on surfactant quantity and time. Obtained latexes was characterized by particle size measurements, viscosity and surface tension measurements. In addition, molecular weight of the polymers were determined by GPC. High solid content water-based emulsion polymerization studies were performed in the another part of the thesis. Latexes produced by emulsion polymerization are versatile materials. It extensively used in very different industry such as adhesives, coatings, textiles, paper paints, floor polish and makeup. The solids content of the latexes produced in the industry is between 50-55%. High solids content (HSC) brings many advantages, such as maximizing reactor production, minimizing transportation and storage costs, providing greater flexibility in product formulation and improving surface coverage when applied. The increase in solids content negatively affects the latex viscosity. This also affects the heat removal rate, mixing ability, mass transfer and product stability. The way to obtain low viscosity (HSC / LV) high solids content is achieved by controlling the particle size distribution (PSD). Particles in a perfect monodisperse latex will contact the solids content of about 64% theorically. This explains that most industrial processes with relatively narrow particle size distribution generally operate at less than 55% by weight of solids content. Bimodal particle size distribution production is considered to come from above this limitation and to achieve the goals of high solids content and low viscosity. In this thesis, two different methods were used to produce twelve different high solid content emulsion polymerization. Firstly 42 nm seed emulsion was prepared by semi-continuous polymerization. Seed emulsion was grown with pre-emulsion via feeding. After the firstly added seed is required to grow, a precise amount of seed was introduced into the reactor shot wise, keeping the feeding of monomers, surfactant and ammonia to reach the desired solids content. Secondly, primary seed was not used in second method. The rest of experiment conditions are same with first method. 65% solid content latexes are obtained. The latexes were characterized by using, Brookfield viscometer, tansiometer, Zetasizer Nanaoseries NS. Unimodal particle size distributions were obtained at the final product that is produced with first method. Viscosities of these products are quite high, compared with other method. The surface tension of these products raise with increasing solid content. Another products which are produced second method, has bimodal particle size distribution. Viscosities of these products are quite low, due to bimodality. The surface tension of these products has nearly same values because of surfactant amount. To sum up, high solid content low viscosity bimodal and unimodal particle size distribution emulsion polymers were synthesized.
Synthesis, characterization of PVC-graft-calixarene molecules and investigation of interactions of saw transducers with volatile organic compounds
In this thesis study, influence of surface coatings of PVC grafted t-butylcalix[6]arene on the sensitivity of surface acoustic wave sensors were investigated. For this purpose, PVC grafted p-tert-butylcalix[6]arene were chemically synthesized through the copper catalyzed azide-alkyne cycloaddition reactions. At the beginning of synthesis stage, PVC was functionalized by substitution reaction of chloride with azide groups and chemical structure was revealed by FTIR spectrometry. On the other side, p-tert-butylcalix[6]arene was alkylated with propargyl bromide using K2CO3 and characterizations which include NMR and FTIR have been carried out. Finally, these separately synthesized materials were reacted through the copper catalyzed azide-alkyne cycloaddition reactions. Chemical structure of PVC grafted t-butyl-calix[6]arene was characterized by using NMR and FTIR spectrometer. Coating solution was prepared by dissolving the synthesized material in DMF and it was coated on ST-cut SAW devices by electrospray coating technique. In order to observe effect of the coating thickness on sensor responses, three different SAW sensors which have different coating thickness were obtained by changing exposure time of solution. An experimental system has been designed to be used in this project in which examines the ability of the PVC-modified calixarenes to retain volatile organic compounds in nanogram concentrations. Sensitivity of the SAW sensors to volatile organic compounds was measured in this computer controlled gas flow and mixture system. Sensing properties of PVC grafted thin films were studied towards volatile organic compounds which were include acetone, ethanol, hexane, heptane, chloroform, toluene. Variation of the responses of the SAW sensors was investigated according to the coating layer thickness and interaction parameters between sensing layer and gas analyte. The influence of interaction of various functional groups with calixarene molecule to sensitivity has been analyzed, as well. In conclusion, it is aimed to study the effects of coated layers on the SAW transducer surface and the sensor properties of the SAW transducer. Therefore sensitivity, repeatability and detection performance of SAW sensors were measured by exposing of PVC grafted thin films towards VOC at variable concentration ratios.
Flame retardant nanofibers from acrylonitrile, methylacrylate and vinylphosphonic acid terpolymers with using electrospinning technique
Polymers have been used many areas in our lifes with manufacturing different production methods. Due to the polymers have some advantages such as low cost and light weight so these advantages make them preferable material in many areas. Nanotechnology also effected our lifes and polymers can be used as a raw material for nanofiber production via different production methods. Electrospinning is one of the suitable nanofiber production method which is very proper and simple way to create versatile properties of nanofibers. Besides this developments, some disadvantages of polymers must be considered such as flammability. Due to the organic based structures of polymers that can be easily burn and cause very big bad results. To avoid fire conditions, flame retardant materials can be used as an additive during production of polymer products. Flame reterdant additives can be halogen, halogen free or inorganic. Halogen flame reterdants have a toxic gases during combustion and hazardous effects. For this reason, halogen free flame reterdants should be used to avoid toxic gases release to the enviroment. This study can be seprable into two main parts. The first part purpose is to synthesize and characterized acrylonitrile (AN), methyl acrylate (MA) and vinyl phopsponic acid (VPA) homopolymer, copolymers and terpolymers. And the second part is to produce nanofibers via electrospinning method with using synthesized polymers and add a flame retardant property to the produced nanofibers. For first part, initially homopolymer of PAN was synthesized. Then with different percentage of initiator to chain transfer agent ratio was used to synthesize copolymers and terpolymers under same reaction conditions. Synthesized P(AN) homopolymer, P(AN-MA) copolymers and P(AN-MA-VPA) terpolymers were characterized using Fourier Transform Infrared spectrometer (FTIR), differential scanning calorimeter (DSC), and thermal gravimetric analysis (TGA). The effect of MA and VPA content on the spectroscopic and thermal properties of AN-MA copolymers and AN-MA-VPA terpolymers were investigated. In the second part of study, elecrospinning process of the homo PAN, AN-MA copolymer and AN-MA-VPA terpolymers solutions in dimethyl formamide (DMF) was prepared succesfully. Morphology of nanofibers was determined with using Scanning Electron Microscopy (SEM).
Synthesis of poly(ethylene glycol) based liquid crystalline mesogen and investigation of liquid crystalline properties
Liquid crystals; between the liquid and the solid phase, exhibit the properties of both the mobility of the molecules and the anisotropic properties of the crystalline solid phase. Liquid crystals are divided into two classes, called lyotropic and thermotropic, depending on the orientation of the molecules in the mesophase. Thermotropic liquid crystals; they are divided into subgroups as low molecular weight, discotic (disk shaped) and calamitic (rod) and high molecular weight (polymeric) main chain liquid crystal polymers and side chain liquid crystals. Click chemistry has gain attention in last decade due to applicability of the reactions in wide range of areas. Side chain liquid crystals can also be prepared via click chemistry reactions. In this thesis, two series of a new poly (ethylene glycol) (PEG500 and PEG750) based rod-like liquid crystal linked via 1,4-disubstituted 1,2,3-triazole ring was synthesized using click chemistry. Firstly, azide-terminated poly (ethylene glycol)'s were synthesized and then, reacted with prepared cyanobiphenyl based liquid crystal mesogen having terminal alkyne moiety. Synthesis of azide terminated poly(ethylene glycol) (PEG) was performed through two-step modification reaction; the first step is sulphonation of hydroxyl functional group of PEG and the second step azidation of tosyl functional group. The characterization of synthesized products was obtained by using Fourier-transform infrared (FT-IR) and 1H-NMR analysis. Liquid crystalline properties and mesophases were investigated by using differential scanning calorimetry (DSC) and polarized optical microscopy (POM). Reaction steps were analyzed by using 1H-NMR and FT-IR spectroscopy. Results have showed that reactions were successfully obtained. POM studies showed that prepared cyanobiphenyl based liquid crystal mesogen does not show any liquid crystalline phase during heating and cooling cycles. Phase transition from crystal to liquid and liquid to crystal phases was observed at high temperature. On the other hand, PEGylated-cyanobiphenyl liquid crystalline mesogens have showed liquid crystalline mesophases at very low temperatures. PEGylated-cyanobiphenyl liquid crystalline mesogen of PEG500 exhibited liquid crystalline mesophase at -60°C and liquid crystal phase transition to isotropic phase at -7 °C during heating cycle, while PEGylated-cyanobiphenyl liquid crystalline mesogen of PEG750 showed that two different liquid crystalline mesophase.
Investigation of mechanical, thermal and flame retardant properties of glass fiber reinforced PBT and PBT/PET blends
Engineering plastics are used more and more areas in a wide spread manner. Especially, need of special performance characteristics, engineering plastics are come to mind. These special characteristics can be defined as high mechanical properties, high abrasion resistance, high electrical and thermal resistance, improved fire retardant performance. Plastics are used in different significant areas such as aeronautics and space, construction, defense industry, automotive, electrical and electronical industry etc. Improvement of mechanical, thermal and fire retardant performance of these engineering plastics, become more of an issue. In order to reach these desirable performance characteristics, manufacturers use reinforcement agents and additives. Glass fibers are commonly used to support polymeric structure with the purpose of obtain stiffness, strength and flexibility. Glass fiber reinforced engineering plastics have also varied fire behavior depend on resins which are used. Previous studies show that scientists had preferred halogenated flame retardants because of their outstanding fire retardant performance in case of fire. By the reason of legislative restrictions (such as REACH), environmental and health considerations, halogen free flame retardant additives have become more and more important. Also, high temperature stable mineral fillers are used to improve thermal properties. The combination of halogen free flame retardants and mineral fillers, give a new impulse to fire retardant performance of engineering plastics. This combination also reduces the cost of high fire retardant performance plastics. Poly(butylene terephthalate) (PBT) is preferred among engineering plastics with its high dimensional stability, low moisture absorption, productivity and fast cycle time characteristics. However, glass fiber reinforced PBT grades have preferred due to modified mechanical properties. Glass fiber reinforced PBT/PET blends have desirable properties such as glossy surface appearance, high rigidity, high temperature and strength properties. Additionally, the most important characteristic of glass fiber reinforced PBT/PET blends is good cost-performance ratio. After the restriction of halogenated based flame retardant, halogen free high performance phosphorus based flame retardant additives are preferred to use in engineering plastics. In this study, samples were prepared by using co-rotating twin screw extruder and they were shaped by injection moulding machine. A halogen free phosphorus based flame retardant additive which is called aluminium diethyl phosphinate is used as main flame retardant. This halogen free phosphorus based flame retardant is also called DEPAL and especially identified as AlPi – Et in scientific researches. Two aluminium based mineral filler are used as a co-flame retardant which has the same chemical structure but they have different average particle size and specific surface area. In first stage of experiment, Actilox B60, which its particle size is 1.2 m, aluminium based mineral filler is used as co-flame retardant. In second stage of experiment, Actilox B30, which its particle size is 2.3 m, aluminium based mineral filler is used as co-flame retardant. This aluminium based mineral flame retardants are boehmite originated and its chemical formula is AlO(OH). All samples contain totally 20% flame retardant additives except control sample. The samples were extruded with different matrices which are neat PBT, glass fiber (GF) reinforced PBT and GF reinforced PBT/PET blend. In order to determine optimum combination of main flame retardant/co-flame retardant, five different ratios are selected. In first stage of the experiment, Actilox B60 is used and these main flame retardant/co-flame retardant ratios are aligned as 20% DEPAL/0% Actilox B60; 15% DEPAL/5% Actilox B60; 10% DEPAL/10% Actilox B60; 5% DEPAL/15% Actilox B60 and 0% DEPAL/20% Actilox B60. In second stage of experiments, samples were prepared with Actilox B30 as co-flame retardant and the main flame retardant/co-flame retardant ratios are 20% DEPAL/0% Actilox B30; 15% DEPAL/5% Actilox B30; 10% DEPAL/10% Actilox B30; 5% DEPAL/15% Actilox B30 and 0% DEPAL/20% Actilox B30. Structural properties of samples were evaluated by measurements of density and melt flow index (MFI). In order to obtain mechanical properties of samples; stress at break, tensile modulus, strain at break and Izod impact (+23 °C and -30 °C) values are calculated. Thermal properties of samples were investigated by heat distortion temperature (HDT), thermal gravimetric analysis (TGA) and differential scanning calorimeter (DSC) analysis. Flame retardant performance of the samples were obtained by UL 94, glow wire ignition temperature and glow wire flammability index tests. In consequence of all experiments; Sample 27, which is contained 5% DEPAL/15% Actilox B30 in 20% GF reinforced PET/PBT blend matrix, is given the best mechanical, thermal and fire retardant performance results.
Step-growth polymerization of formaldehyde and paraformaldehyde with amine monomers for preparing monolithic capillary columns
Monolith structures are a big research area of material science with different forms and usages. Monoliths are kind a controlled structure to select some analytes which wants to separate. Monoliths are maden from different materials like silica or polymers. Polymer materials have a wide range applications. Polymers had place of metals and some other materials because of their production methods and chemical properties. Polymeric monoliths are mostly in membrane or column form. Membrane types monoliths produce for enviromental industry or health industry. Seperation could be possible for membrane types monoliths by molecularly imprinting technology. Imprinting technology is like a molding of deserved chemical with a structure of polymer. This provide lots of chemial structure can be separate with monolith structures. Just the important part is matching suitable polymer structure with a suitable mold molecule. Column type monoliths are main research area of seperation technology. After chemical processes developed amount of chemicals inside the mixtures were wanted to analyse with different ways and for analyse seperation is necessary. Chromatographic analysis are main driver of that purpose. Chromatographic analysis are combination of seperation technology with a dedector to calculate amount of analytes. Seperation should be perfect for amount analysis of chemical structures Columns are the most important part of that analysis with different structures. Polymer columns are mostly prepared with in-situ polymerization which means synthesis of polymer inseide of column. And polymer should stay inside of column with high pressures. Monomers and template molecule for imprinting are sending inside of column at same time as a homogenious solution to obtain uniform column. Template molecules can be deserved analyte for analysis or a different analyte with similar structure. For health analysis it is not possible always to find same structure with deserved molecule so similar strucure are used for molecular imprinting. Analysis for cancer diagnostics aim is a new study topic now. For that analysis phospopeptide structures are the most used template molecules. That study is a prestudy of preparing a new type phospopeptide imprinted monolithic cappilary column by polycondensation. For this purpose different amine monomers have used for copolymerization. The amine monomers which have used; biguanide, guanide, biuret and biurea. There was not any new study about this monomers forcopolymerization of formaldehyde so firstly suitable polymerization conditions should be found .Investigation of that condtions is a complicated process.Polymerizayion at high temperature is not possible for molecular imprinting because of structure of template molecules. Bulk format polymerization inside the glass vials have investigated before in-situ polymerization to find best conditions for polymerization. FT-IR analysis have maden to investigaste functional bonds. Spectra showed absorbances of expected bonds. Different temperatures, different amount of monomers and different polymerization times have tried for each monomer. BET surface area analysis have maden for some polymers. Higher amounts formaldehyde and polymerization time above 1 hour caused higher surface area. Before in-situ polymerization, wall of columns have prepared by silanization to making active for keeping polymer inside under high pressures. Mostly APTMS is used for silanization of columns. Different amount of APTMS have tried for that study. Columns have tried with HPLC pump and methanol have used as mobile phase to see silanizasyon results. And the most effective pretreatment ways found. SEM images of that columns have taken to see interaction of column and polymer. That discovered; % 50 amount of APTMS with 80 oC silanization temperature was the best one. And also solvent concentration which are used before APTMS for washing column is also has a little effect for result of silanization. Columns are suitable for high pressure liquid chromatography but molecular imprinting results should investigate more. From all that results it was clear that Phenyl-biguanide and paraformaldehyde polymer monoliths could be useful for preparing phospopeptide imprinted columns by polycondensation. But still there is a lot to do for finding useful columns.
Preparation of urethane modified poly(styrene) based resin for removal of phenol
The human being is influenced by the quality of water resources in the natural environment. In order to guarantee a secure and healthy life, the water consumed must be free from harmful chemical substances. The water released into the environment by water purification plants and private organizations should be regularly accessed and examined to maintain complete yielding to water framework act. Thus, treated waters should be safe for consumption and free from harmful compounds to guarantee a healthy life. However, there are environmental organizations for water quality which have given standards to ensure that water is free from contaminants, thus making safe water consumption possible. Water treatment requires adequate analysis and monitoring which includes determination of low level contaminants. The maximum level of contaminants which present in drinking water should be so small that the effect is harmless to human health. Thus analytical methods are important to quantify the contaminants. Phenol and derivatives are harmful substances found in water. Moreover, faced with more and more stringent regulations, the water contamination has also become noteworthy source of concern and priority for most industrial sectors. Phenols are aromatic components which contain one and more hydroxyl groups connected to aromatic ring. Phenol is a benzene derivative having chemical formula of C6H5OH with a structure of a hydroxyl group bonded to the phenyl ring. It is a colorless, crystalline substance of characteristic odor, soluble in water and organic solvents. Phenols are similar to alcohols but form stronger hydrogen bonds. Thus, they are more soluble in water than alcohols and have higher boiling points. Phenol was prepared mainly from coal tar, in the early 19th century. Presently, small quantities of phenol is still obtained from coal tar. The demand for phenol grew significantly with the commercialization of phenolic resin (Bakelite), during the 20th centuries. An advanced and popular phenol process is Hock Process after the World War II. It is currently the predominate route for the production of phenol which is accompanied by acetone as a co-product. The main commercial plant utilizing toluene as the feedstock was launched in the 1960's. Nowadays, the commercial production of phenol is not obtained from toluene. Phenols are used in many industrial activities for the production of pesticides, insecticides, herbicides, and synthetic products. Phenols in which certain amount of pesticides and wood preservatives contain can lead to specific health damages even at the lowest concentration levels. Some harmful effects of breathing phenol from the air have been occured for human. Short time effects of phenol include breathing infection and eyes burning. The chronic effects of high exposures cause muscle aches, weak spots, weight loss. Effects of long term and low level exposures cause to increases in cancers and effects on the immune system. Nevertheless, it is important to be aware of phenols and substituted phenols in environmental and biological samples. Many different techniques are used for the removal of phenol from wastewater. The methods can be separated into three categories: chemical, biological and physical. All of them have advantages and disadvantages. Because of high cost and disposal problems, many of these conventional techniques for treating phenol bearing wastewater have now not been widely applied at large scale in the textile and paper industries. Adsorption of phenol has three mechanisms; π-π dispersion interaction, electron donor-acceptor complex formation and hydrogen bond formation. In this thesis these mechanism were applied to synthesis new polymeric resins for phenol removal. Two types of polymeric resins were prepared for adsorption of phenol from the water. In the first part of this study, The Resin 1 was obtained with chloro-sulfonated polystyrene (CSPS) and it excess of ethanolamine. The resin was characterized with analytical methods and FT-IR spectroscopy to determine the functional groups. The Resin 2 was prepared through a reaction of the Resin 1 with butyl isocyanate in dimethyl formamide (DMF) solution. Polymers were characterized by using analytical methods and FT-IR. In the second part of the study, experimental measurements were performed on modified resins for phenol adsorption. The phenol sorption capacities of the resins were described by mixing 0.1 g polymer samples (resin1 and 2) with 10 mL phenol solutions with various concentrations (0.5 M, 0.35M, 0.25 M, 0.1M, 0.05 M, 0.025 M and 0.01 M). The phenol loading capacities were calculated from the initial and ending phenol contents of the solutions. Also, kinetics of phenol sorption was performed at low concentration to investigate the efficiency of the modified resin at trace concentration. For this purpose, pseudo-first order, pseudo-second order and intra particular diffusion kinetics models were used.
Research on the mechanical and morphological properties of microfibrillar reinforced PET/PP blends at various processing routes
Polypropylene (PP) is one of the commodity polymers used in a number of industries including packaging, automotive, infrastructure, and textile. However, because of its low mechanical properties, there are some restrictions in its application ranges. Compounding with functional fillers like glass fiber can greatly enhance the mechanical properties of PP. However, this kind of filler is abrasive for production line, not eco-friendly and expensive. Because of that in today's market conditions, producers have been looking for a way to provide more economic and eco-friendly solutions. In recent years, polymer blending has become an economic way for preparing new materials. Some advantages of blending can be listed as below; • Blending can offers customer-driven product design opportunity. • The properties of matrix polymer such as flame resistance, toughness or dimensional stability can be improved. • Blending can offers a way for recycling of industrial plastic wastes. • Blending with low viscosity polymer can improve processability. • Blending can provide to increase of productivity. • Additionally, blending technology can be also used in multi-layer structures. In plastic industry, different ways are used to prepare polymer blends such as melt blending, block or graft copolymerization, melt solution. However, among of these techniques, melt blending is the most commonly used method to achieve desired properties. This method offers opportunity to prepare polymer blends in more economically. As known, most of polymers are thermodynamically incompatible due to differences in their chemical structure. Therefore, during the mixing numerous types of phase morphologies such as fibrillar, droplet or laminar occur and, final properties of blend strongly depend on this morphology. For example, laminar structure of the dispersed phase which is often generated via film extrusion or blow molding improves the barrier properties of blend, whereas fibril structure enhances the mechanical properties. In resent years, a new type of material named as microfibrillar reinforced composites (MFCs) based on blending of two immiscible polymers have been developed. In this materials, to achive higher mechanical performance, minor phase is dispersed in fibrillar form in the matrix polymer. In contrast to the common composites, MFC materials can prepare without any inorganic additives. Additionally, this technology offers opportunity to weight reduction and easy recyclability in comparison to glass fibre reinforced composites. The main aim of thesis study is to produce microfibrillar reinforced PET/PP blends and investigate the effects of various parameters such as screw speed, process temperature, drawing method, drawing ratio, PET content and compatibilizer on the morphological and mechanical properties. In study, microfibril reinforced composites were prepared by a three step process. In the first step, two polymers were blended in a twin screw extruder. In second step, to obtain PET fibers, the extrudate was stretched. In last step, to achive MFC material, drawn PET/PP blends (MFB) were pelletized and molded by injection molding. After each stage of MFC production, analyzes were carried out by scanning electron microscopy (SEM), wide angle X-Ray diffraction (WAXD) and mechanical tests. At the beginning of study, to determine appropriate screw rate for blending, PET and PP were mixed at various screw rates. It was observed from the SEM images that lower or higher screw speeds than 300 rpm were not suitable to obtain homogeneously dispersed blend morphology. In second step of study, to generate microfibril reinforced blend (MFB), two different stretching methods were used. In the first method, the extruded blend was stretched between the first godet and extruder die by increasing rotation speed of first godet. In the second method, the extruded blend was stretched between the two godets. According to the analysis results, reinforcer polymer was able to successfully distributed in fibrillar shape in both methods. However, in second method higher mechanical properties were achieved as a result of well orientation of both component of blend. Depend on the PET concentration and applied draw ratio, the tensile properties of MFB samples greatly increased almost 6-7 times higher than extruded blends. In study, the influence of compatibilizer and its amount on the blend properties were also investigated. SEM images showed that after adding of compatibilizer, maleic anhydride grafted polypropylene (PP-g-MA), more uniform blend morphology was occured. Additionally, adhesion between the PET fibers and PP matrix was improved through compatibilizer and thus, mechanical properties increased. In the last step of study, in order to achive microfibril reinforced PET/PP composites, drawn blend samples were molded at different injection temperatures. SEM images showed that even though injection temperature was set to temperature which is lower than melting temperature of PET, many of fibers lost their shapes and returned into droplet structure. Despite this, better impact resistance and tensile properties were observed in comparison with extruded blend. In conclusion, when take into consideration three stage of microfibrillar reinforced polymer composites (extrusion, drawing and injection molding), the presence of PET fibers caused to increased mechanical properties of extruded blends but the highest increase was obtained in drawn blend samples. Therefore besides of MFC materials, MFBs may also offer an opportunity for industrial applications. For example, it can be weaved like technical textiles or it can be directly winding on products like plastic pipe. On the other hand, MFCs can be used in injection molded plastic pipe parts called as fittings.
Synthesis of reactive polyurethane adhesives and studying the effect of ketonic resins
Polyurethanes were first discovered by Otto Bayer and his colleagues at the end of the 1930s. It was soon learned that polyurethanes could adhere rubber to metal and so polyurethane adhesives containing polyester polyols have been developed rapidly. Many studies have been made to synthesize polyurethane adhesives until today and now it is widely used for bonding many materials such as rubber, plastic, metal, wood, glass and ceramics. Nowadays, polyurethane adhesives have very good hydrolytic stability, excellent low temperature performance as well as cost advantages. Although the performance at high temperatures is not sufficient, the application areas are narrowed to a certain extent, but recent developments are quite encouraging. The one-component reactive polyurethane adhesives subject to study are widely used especially in the furniture sector. One of the most important parameters affecting the productivity of the furniture producers is that the parts joined by bonding are waiting for long time and cannot be subjected to any processing during this period. In this case, the productivity of the production decreases. Ketonic resins are used as a resin in the ink and paint sector in an intensive adhesion. Many successful products that use ketonic resins in this direction are commercially available in our lives. However, their use in polyurethane adhesives has not been the subject to date due to the fact that ketonic resins are more difficult to access than polyols and the costs associated therewith are high. In this study, the effects of cyclohexanone formaldehyde ketonic resin (CFR) with different montmorillonite content on the viscosity, initial adhesion strength and temperature resistance of polyurethane one component adhesives were investigated. Two different blanks were synthesized with NCO/OH ratio 4.84. Polyether polyol and polymeric 4,4'-methylene diphenyl diisocyanate (p-MDI) were used only to synthesize the polyurethane pre-polymer/adhesive blanks. In the first case, plasticizer was used to adjust the viscosity and to reduce the fragile structure of the product. Montmorillonite clay containing (MM-CFR) and not containing CFR are synthesized like blanks with and without plasticizer. CFR and MM-CFR at a rate of 10% by weight of polyether polyol were used. In parallel with the reduction of the amount of polyether polyol used, the ratio of isocyanate groups (NCO) to hydroxyl groups (OH) was 5.38 (CFR and MM-CFR ketonic resins were not involved in calculation). The completion of reaction was followed by FT-IR device. Polyol has a characteristic peak corresponding to OH groups at 3400 cm-1. The peak disappears with the completion of reaction. The NCO % values of the synthesized products were measured with an automatic titrator and this value decreased with the use of CFR and MM-CFR. It has been found that the NCO % value tends to decrease with the increase in the amount of MM clay in the CFR. In fact, it is expected that the NCO % will increase with the increase of the MM clay amount. How the strength values are affected by the use of CFR and MM-CFR and the time-dependent variation of strength were investigated. It was observed that the build-up of green strength and the final strength are both better than blank samples. It was observed that the viscosity of the products synthesized increases in parallel with the increase of the MM ratio and CFR. Viscosity increase is an undesirable situation. The product viscosity remained at acceptable levels with incorporation of chloroparaffine. When TGA data were examined, it was found that the heat resistance of the product increased with the addition of CFR and MM-CFR. The increase in the amount of MM clay in the CFR appears to have a positive effect on the results. In this case, the use of CFR and MM-CFR may be appropriate in applications where temperature resistance is required. When DSC analyzes were examined, it was determined that the products which thermoset after curing were stable and did not decompose at the temperature range in which the analysis was carried out. The results were similar to TGA data. As a result of the experiments, adhesion properties and thermal stability of one component PU adhesives are found to be improved with incorporation of CFR and MM-CFR. In addition, the viscosity build-up of the adhesives with increasing amount of clay content in CFR can be overcome with plasticizer. The results encourage us that CFRs with increasing amount of montmorillonite clay can be a good alternative to improve adhesion properties and thermal stability without viscosity problems.
Effect of soft segment length on foam structure of expanded thermoplastic polyurethane (ETPU) bead foams
Since the second world war, many types of polymers and their products have been produced. This is because of their broad range of properties compared to other materials such as metals and composites, including toughness, viscoelasticity, and a tendency to form glasses and semicrystalline structures rather than crystals. The most prominent features of polymers are, however, their low density, ease of manufacturing, and hence cost-effective. Thermoplastic polyurethane (TPU) is a thermoplastic based elastomer, which means it is meltable and processable when heated, formable and shapable when cooled, and capable of being reprocessed multiple times. TPU is well-known for its many features including; high abrasion resistance; flexibility over a wide range of temperatures; high tensile strength; good resistance to weathering; good resistance to oil, grease, solvents and chemicals. These properties make TPU extremely useful for hundreds of applications such as automotive instrument, caster wheels, power tools, sporting goods, medical devices, drive belts, footwear, and a variety of extruded film, sheet and profile applications. TPU is a block copolymer including alternating sequences of hard and soft segments formed by the reaction of diisocyanates with short-chain diols and diisocyanates with long-chain diols. By varying the ratio, structure and/or molecular weight of the reaction compounds could be changed, and different TPU with varying properties can hence be produced. This allows to tailor the desired final properties of the material. For instance, a greater ratio of soft segments to hard segments will result in a softer TPU, while the reverse will result in a more rigid TPU. The polyol chain of TPU can be either polyether based or polyester based. Polyester TPUs are compatible with polar plastics, offer a good balance of physical properties and are perfect for use in polyblends. Polyether TPUs are slightly lower in specific gravity than polyester. They offer low temperature flexibility and good abrasion and tear resilience. They provide excellent hydrolysis resistance – making them suitable for applications where water is a consideration. TPUs can also be subdivided into aromatic and aliphatic isocynates. TPUs with aromatic isocynates like Methylene diphenyl diisocyanate (MDI) can be used in applications that require flexibility, strength and toughness. TPUs with aliphatic isocyantes like-Methylene dicyclohexyl diisocyanate (H12 MDI), hexamethylene diisocyanate (HDI), and isophorone diisocyanate IPDI are commonly used in projects where optical clarity, adhesion and surface protection are required. Polymeric foams are made up of a polymer matrix with either closed bubbles (cells) or interconnected tunnels, which are known as either closed-cell or open-cell structures. Open-cell foams are mostly flexible, while closed-cell foams are generally more rigid. The gas that is used in the foam is known as blowing agent, which can be either chemical or physical. Physical blowing agents are gases which do not react chemically in the foaming process, while chemical blowing agents take part in a reaction or decompose, giving off chemicals in the process. Polymer foams can be divided into either thermoplastics or thermosets, which are further divided into rigid or flexible foams. The thermoplastics are usually breakable and able to recycle, while thermosets are harder to recycle because they are usually heavily crosslinked. The first polymer foam was foamed polystyrene in the 1930's. During second World War polyurethane was invented. After the war, the flexible polyurethane foam was produced and used for furniture and automotive industry. In the following years, polymer foams were more widely used as new technologies developed, such as injection molding and several extrusion techniques. Recenlty, bead foaming technologies are developed including several methods, for instance foam extrusion with underwater pelletizer, suspension polymerization with blowing agent, and batch foaming process. Batch foaming is noncontinuous process that is qualified to study the foaming behavior of polymers and also exist for industrial applications. In this process, polymer is firstly saturated with physical blowing agent in a high pressure cell. Later, foaming is initiated by either a pressure drop or increase in temperature which results in a thermodynamic disequilibrium. In pressure drop method, pressure drop rate effect on the cell nucleation can be investigated, while increase in temperature method suits to evaluate the processing window of the polymer. The reason why polymer foams are widely used is that they have a lot of advantageous such as low density, cheaper, tailored properties which could influence the final funactional properties such as insulation properties. Bead foams have an extra advantages compare to foam extrusion and foam injection molding, which is its ablity to form low density three dimensional complex geometry foam products. This thesis focus on foaming behavior of expanded thermoplastic polyurethane (ETPU) through batch foaming process. TPUs samples that have different molecular weights and different polyol types are examined. The effect of process conditions; saturation pressure, time and temperature on foam morphology; also, the effect of pressure drop rate on cell nucleation are investigated. At first, to investigate the onset of degradation and thermal decomposition behavior, TPU samples were analyzed by thermal gravimetric analysis (TGA). To know the materials better, the rheological properties of the TPUs were also measured using a rheometer under oscilatory shear loads and using melt flow indexer. Later, the effect of molecular weight and polyol types of TPU on the crystallization behavior was expolered with non-isothermal melt anaylsis in differantial scanning calorimetry (DSC). The next step was isothermal crystallization analysis in DSC, which simulates foaming process without blowing agent, to understand how isothermal annealing in DSC can modifie the crystals and influence the cell nucleation. After the thermal analysis, samples were foamed at different temperatures under 2000psi for 30min to find the optimum process temperature. When optimum temperatures were determined for all samples, they were also foamed at 1000psi and 1500psi for 30 min to manitor the saturation pressure effect on TPU's foaming behavior, also at 2000psi for 15min and 60 min to investigate the saturation time effect. Furthermore, to understand how the hard segment crystals were modified by isothermal annealing under CO2, all process conditions were repeated with extremly slow pressure drop rate that would not cause foaming for all samples. The foamed TPU samples were characterized in two aspects. Firslty, the density of foamed samples and their expansion ratio were measured in pure water and calculated using archimedes equation. One the other hand, the morphology of cellular stucture in foamed samples were observed using scanning electron microscope (SEM). After the observation of cellular morphology; cell distributions and cell dimensions were examined and the cell density of each of samples was calculated. Thermal analysis performed for foamed samples by DSC to monitor the foaming effect on further modification of hard segment crystals.
Synthesis of cellulose acetate butyrate based polymeric films and their applications
Cellulose is a bio-polymer that is the most abundant as raw material and is widely used in many commercial applications. The conversion of cellulose into regenerated cellulose can be occurred via the formation of ester and ethers by the reaction with various chemical species. In other words, the modification of raw cellulose, in the way of desired physical/chemical properties required for the usage area, is performed by adding functional groups. The hydroxyl groups that are extensively found in the cellulose structure, allow the mentioned modification processes. The most important commercially available cellulose ester derivatives are as follows; cellulose acetate, cellulose acetate propionate and butyrate, carboxymethyl cellulose acetate butyrate. Cellulose esters show various properties such as flexibility, rigidity, solubility, water/solvent resistance, bio-degradation, viscosity etc. depending on the chemical structure. This issue was given in literature review section in detailed. Besides the superior physical/chemical properties, cellulose esters have also some disadvantages that restrict their usage area. For instance, low solubility property of cellulose acetate in common solvents (ethyl acetate, 1,2-dichlorometan etc.), the hydrophobicity of carboxymethyl cellulose acetate butyrate, high viscosity of cellulose acetate butyrate in molten state and having low thermal stability. All these drawbacks of cellulose esters require the chemical modification processes or using them as blends with various polymers. Researches regarding to solve these drawbacks were given in further sections. As mentioned in literature review, the chemical modification of cellulose esters is important in terms of the synthesis of oligomers with desired properties that are suitable for the usage area. Among all cellulose derivatives, cellulose acetate butyrate (CAB) shows some superior properties such as high scratch resistance, suitable for food industry, and being economical. The CAB crystals in rod structure give a good gas barrier property. But, as mentioned before, the high viscosity of CAB in molten state restricts the processability property of CAB. Besides that, the low thermal stability of CAB leads a narrow processability range between the melting and decomposition temperatures. Researches regarding the solution of these problems are so limited in literature and there is no research considering the modification of the CAB by using urethane based oligomers. In this study, it was aimed to add UV-sensitive acrylate and carbamate ester groups to the CAB chain with the modification of toluene diisocyanate - hydroxyethyl methacrylate (TDI-HEMA) adduct via the hydroxyl groups in CAB structure, without changing the superior properties of CAB. The hydroxyl groups in CAB structure will be reacted in various percentages, and then the contribution of the hydroxyl groups, that are left unreacted, on adhesion and wettability properties will be investigated. The mechanical and chemical properties of UV-cured free films of TDI-HEMA modified CAB oligomers will be searched. Then the nano-fibers of these oligomers will be obtained by electrospinning method and cured by UV-light. The obtained nano-fiber surfaces will be investigated in terms of the gas/moisture permeability properties based on the standards (ASTM, ISO etc.) that are needed for food industry. Coating formulations will be prepared by using TDI-HEMA in various percentage reacted with hydroxyl groups on CAB oligomers. The effects of TDI-HEMA percentage on CAB morphological/mechanical properties, and gas/moisture permeability values of electrospun fibers surfaces will be observed. There are numerous researches regarding the nano-fiber production from cellulose derivatives and have been told in literature review. But the usage of UV-curing technology about this issue is so limited. The reason of using electrospinning method is that, the opportunity of an accurate controlling the coating thickness during the electrospinning process. UV-curing technology is favored due to the requiring none or less solvent (environment friendly), processability at low temperatures (economical), and saving of time with a rapid crosslinking mechanism just in a few seconds (mass production). In this study, the effects of urethane functionality percentage on coating formulations prepared by using TDI-HEMA modified CAB oligomers, the number of the hydroxyl groups left unreacted in CAB chain, electrospinning parameters on the properties of final product will be examined.
Tübüler kompozitler için polimer reçine sistemlerinin optimizasyonu
Polymer matrix composite materials are designed and produced according to various needs. Main strategy is to obtain the most appropriate product at the most appropriate costs. Hence various alternative composites are developed according to cost performance ratios. Automotive industry is undoubtedly one of the most challenging sectors. Besides, biomedical sector, superstructure and infrastructure sectors, marine, aviation and space sectors are also concentrated on different performance characteristics of composite materials such as strength and lightness, as well as compatibility, flame retardancy or resistance to chemicals. Though, raw materials such as resin, reinforcers are procured according to the needs in composite production, various strategies are proposed to lower the material costs. One of the basic strategies to lower the costs is to mix the cheaper components to the resins up to a point mechanical performance did not change abruptly. That can be industrial waste, either from the composite industry or else. In the first part of this thesis, the performance of vinyl ester resins was evaluated after mixing with polyester wastes within the facilities. Without sacrificing mechanical values, it was possible to reduce the cost and evaluate the material within the new product. Accordingly, the addition of 10% polyester resin decreased the cost of the product by 6.66%, while the storage module showed higher performance than the reference material without unsaturated polyester resin. The performances of the resin mixtures were measured by dynamic mechanical analysis. After the results, pipe production was performed by helical winding method with a mixture containing 10% polyester resin. It was confirmed that there was no decrease in the mechanical values by both longitudinal tensile tests and circumferential tensile tests (split disk tests). Cost study was calculated by taking into consideration the unit prices of the product. For more realistic results, items such as storage, processing and transport for disposal should be added if they are not used during the 3-month shelf life of the material left. However, these values will vary according to the location of the facilities which we are not included in the calculation. As a second study of the thesis, waste polystyrene (PS) foam, a widely used thermoplastic polymer, was mixed into thermoset resin to evaluate the waste material and reduce the cost of product. Two different approaches were investigated to prepare the mixtures. At first, small pieces of PS foams were directly mixed into vinyl ester resin (VER). In the second, the PS foam was dissolved in the styrene monomer which isused as the diluent for VE resins and then mixed into the resin. It was observed that materials prepared by using both approaches, mechanical values of the test results decreased as well as the glass transition temperature of the material while the amount of PS increased. This result shows that the structure of the polystyrene foam is deteriorated and the vinyl ester bond reduces the cross-link density. The dissolution of the polystyrene foam directly in the vinyl ester resin yielded more favorable results than dissolution in the styrene monomer. Nevertheless, the high viscosity structure formed in the mixtures obtained is an important consideration in the process selection of the product to be produced.
Development of expanded thermoplastic polyurethane (ETPU) bead foams: Dependency of the foam structure on TPU's hard segment content
In this thesis, we focus on bead foaming behavior of expanded thermoplastic polyurethane (ETPU) by using batch foaming process. Because TPU chemical composition and morphology directly affect the foam product features, different hard segments ratio and different polyols types of TPU were examined. Moreover, during the process, the effect of conditions which are saturation temperature, pressure and time on foam morphology were investigated. Cell nucleation phenomena were examined with pressure drop rate. Moreover, gas effect on crystalline segments under different conditions was investigated. Firstly, TPU samples were analyzed by thermal gravimetric analysis (TGA) to understand thermal decomposition behavior and the onset degradation temperature. Also, differential scanning calorimetry analysis (DSC) was used for understanding melting and crystallization behavior of TPU by non-isothermal analysis. According to results, process temperature range were investigated. For understanding the melt behavior and rheological properties of TPU, rheometer under oscilatory shear loads and melt flow indexer were used. To understand crystallization behavior of TPU under certain annealing temperature, isothermal analysis in DSC was used. By using thermal analysis, the temperature range was specified for foaming experiments. Under 2000psi for 30min different process temperatures were run until find reliable value for foaming processing. After finding the process temperature, all samples were foamed at 1000, 1500 and 2000psi for 30min in order to understand pressure effect on foaming. Later, samples were foamed at 15, 30 and 60min under 2000psi for investigating time effect on foam morphology. Furthermore, all foaming experiments were repeated again with very slow drop rate without obtaining foaming structure. Thus, gas effect on crystallization and cell nucleation phenomena were investigated. Finally, the foamed TPU samples were characterized. Firstly, the density of foamed samples and their expansion ratio were measured by Archimedes equation. Secondly, the morphology of cellular structure in foamed samples were observed using scanning electron microscope (SEM). After the analysis of cellular morphology; cell density and cell size were calculated for each samples. Hard segment effect on cell density and size were observed. To understand the effect of hard segment, gas under pressure and pressure drop rate on crystallization; thermal analysis was performed
Langmuır-Blodgett ince film üretme tekniği ile hazırlanan polimer tabanlı nano ince filmlerin karakterizasyonu ve zararlı organik buharlara karşı duyarlılığı
Bu çalışmada, α-(naftalin-1-yloksi)-2-oksooetil metakrilat polimeri (Poli-NMA) sensör maddesi olarak kullanılarak polimer bazlı kimyasal sensör geliştirilmiştir. Bu amaç için polimer türevi, Langmuir-Blodgett (LB) ince film kimyasal gaz sensör elementi olarak tasarlanmıştır. Poli-NMA maddesi Fourier Dönüşümlü Kızılötesi (FTIR), 1 H-NMR (Nükleer manyetik rezonans) ve 13C-NMR analizleri ile karakterize edilmiştir. Bütün Poli-NMA LB ince filmleri Atomik Kuvvet Mikroskobu (AKM), UV-Görünür Bölge Spektroskopisi ve Kuartz Kristal Mikrobalans (KKM) teknikleri ile karakterize edilmiştir. Polimerik kimyasal sensörü KKM tekniği kullanılarak dört farklı zararlı organik buhara (diklorometan, kloroform, benzen ve toluene) maruz bırakılmıştır. Bu çalışmada, ayrıca, Poli-NMA kimyasal sensörünün zararlı buharlara karşı hassasiyet ve LOD değerleri belirlenmiştir. Oda sıcaklığında elde edilen sonuçlar, polimerik kimyasal sensörün zararlı buharlara karşı tepkisinin geniş, hızlı ve tekrarlanabilir olduğunu ve kinetik tepki değerlerinin sıralamasını diklorometan, kloroform, benzen ve toluen olarak göstermiştir.
Ksantan GAM-G-2-(N-Morfolino) etilmetakrilat/titanyum oksit bazlı yeni yarı iç içe geçen ağ yapılı hidrojellerin sentezi, karakterizasyonu ve katyonik boyaların sulu çözeltiden tek ve rekabetçi adsorpsiyonu
Organik boyaların endüstriyel atık sulardan uzaklaştırılması, çevrenin korunması ve canlı yaşamın devamı açısından özel ilgi çekmektedir. Bu çalışmada, titanyum oksit nanoparçacıkları (TiO2) içeren ksantan gamı (KsG)-graft-poli 2-(N-morfolino) etilmetakrilat (MEMA) bazlı yarı-iç içe geçen hidrojelleri serbest radikalik polimerizasyon yöntemi ile sentezlenmiştir. KsG-g-poli (MEMA) ve KsG-g-poli (MEMA)/TiO2%1,5, metilen mavi (MM+) ve kristal viyole (KV+) boyar maddelerinin tekli ve ikili sulu çözeltilerinden adsorpsiyon metoduyla uzaklaştırılması için etkili bir adsorban olarak kullanılmıştır. Gözenekli yapıya sahip olan hidjellerden KsG-g-poli (MEMA)/TiO2%1,5'nin şişme oranı %481,9 iken KsG-g-poli (MEMA)'nın %447,5'tur. Hidrojellerin sıfır yük noktası 7,8 olarak hesaplanmıştır. Boyar maddelerin sulu çözeltilerden uzaklaştırılması davranışlarında KsG-g-poli(MEMA) ve KsG-g-poli (MEMA)/TiO2%1,5 hidrojelleri için MM+ boyasında Dubinin-Raduskevich (D-R) izotermine ve KV+ boyasında Freundlich izotermine uyum göstermiştir. Kinetik çalışmalar, her iki boyanın KsG-g-poli (MEMA) ve KsG-g-poli (MEMA)/TiO2%1,5 adsorbanı ile adsorpsiyonunun parçacık içi difüzyon modeline uyduğunu ortaya çıkarmıştır. İkili sistem çalışmalarında, KV+'nın uzaklaştırılma yüzdesi MM+'den daha yüksek olarak bulunmuştur. Tekli sistem adsorpsiyon kapasiteleri ile karşılaştırıldığında, ikili sistemde her iki boyanın uzaklaştırılan miktarları daha yüksektir. Buna göre, her iki boyanın da KV+/MM+ karışım çözeltilerinden adsorpsiyonları sırasında sinerjik bir etkileşim gösterdiği sonucuna ulaşılmıştır. MM+ ve KV+ boya karışımlarından adsorpsiyonu için en uygun model yalancı ikinci derece model olduğu belirlenmiştir. Dördüncü adsorpsiyon-desorpsiyon döngüsünden sonra bile, adsorbanın boya çıkarma etkinliğinin nispeten yüksek olduğu belirlendi. KsG-g-poli (MEMA) ve KsG-g-poli (MEMA)/TiO2%1,5, kirli suyun arıtılmasında değerli ve yeniden kullanılabilir bir adsorban olabilmektedir.
Doğal bor mineralleri kullanarak radyasyon dozimetresi geliştirilmesi
Bu tez çalışmasında; iyonlaştırıcı radyasyonun bulunduğu bölgelerde yaşayan ve/veya çalışan farklı sektördeki insanların soğurdukları radyasyon dozunun belirlenebilmesi için, doğal bor minerallerinden radyasyon dozimetresi olarak geliştirilmesi amaçlanmıştır. Bu çalışmada Balıkesir'de Bigadiç bölgelerinden farklı bölgelerinden temin edilen doğal bor minerallerinden Kolemanit-1, Kolemanit-2, İnyoit ve Üleksit kullanılmıştır. Kayaç olarak temin edilen minerallerin yapı analizi X-Işını Difraksiyon Yöntemi (XRD) ve Taramalı Elektron Mikroskop (SEM) ve Enerji Dağılımlı X-Işını Spektroskopisi (EDX) analizi ile gerçekleştirilmiştir. XRD sonuçlarına göre, doğal bor minerali Kolemanit-1 ve Kolemanit-2 monoklinik yapıda olup, kristalit boyutları sırasıyla 39,45 nm ve 39,36 nm'dir. Doğal bor minerali Üleksit triklinik yapıdadır ve kristalit boyutu 41,26 nm'dir. Doğal bor minerali İnyoit ise monoklinik yapıda olup kristalit boyutu 39,37 nm'dir. Yapı morfolojisi için SEM analizi, elementel analiz için de EDX analizi gerçekleştirilmiştir. Elementel analiz sonucunda, doğal bor minerali Kolemanit örneğinin yapısında B,O,Sr,Ca elementleri, doğal bor minerali Üleksit örneğinin yapısında C,O,Na,Ca elementleri, doğal bor minerali İnyoit örneğinin yapısında ise O,Ca elementleri tespit edilmiştir. Tez süresince çalışılan doğal Bor mineralleri farklı ışınlama kaynakları ile cGy (1, 2, 3, 4, 5, 6, 7, 8, 9, 10 cGy), Gy (6,9) ve kGy (1, 2, 3, 4, 5, 6, 7, 8 kGy) mertebelerinde ışınlanmıştır. Bu ışınlama çalışmalarına ek olarak örneklerin UV ışınlama çalışmaları da gerçekleşmiştir. Geliştirilmesi amaçlanan radyasyon dozimetresi malzemesinin incelenmesi, ağırlıklı olarak Elektron Spin Rezonans (ESR) Spektroskopisi ile yapılmıştır. ESR için optimum deney şartlarının belirlenmesi için mikrodalga gücü ve modülasyon genliği çalışmaları yürütülmüş ve optimum mikrodalga gücü 1 mW ve optimum modülasyon genliği 1 G olarak belirlenmiştir. ESR spektroskopisinde önemli bir spektral parametre olan spektroskopik yarılma çarpanı g-değeri; doğal bor minerali Kolemanit-1 ve Kolemanit-2 örneği için sırasıyla 2,0021 ve 2,0011 olarak belirlenmiştir. Doğal bor minerali Üleksit örneği için g-değeri 2,0016 ve İnyoit için ise 2,0009'dur. Tepeden tepeye çizgi genişliği ∆Hpp değeri ise Kolemanit-1 için 4,56 G, Kolemanit-2 için 7,10 G, Üleksit için 6,55 G ve İnyoit için 6,32 G'dir. Tez kapsamında incelenen doğal Bor minerallerinin doza bağımlılıklarının cGy ve Gy ışınlamaları için çok düşük olduğu, kGy mertebesindeki ışınlamalar için ise tüm örnekler için ESR sinyal şiddet değerlerinde artış olduğu görülmüştür. İncelenen numuneler arasında doz- cevap bulguları en yüksek olan numune Kolemanit-1 ve Kolemanit-2 olarak belirlenmiştir. Bununla beraber ışınlanan örneklerinin ESR sonuçları detaylandırıldığında, ışınlanan örneklerin bazı radyasyona hassas ve kararlı rezonans piklerinin dozimetrik amaçlı kullanılabileceği sonucuna varılmıştır. Bu bağlamda ışınlanan doğal Bor minerallerinden oluşturulan doz-cevap eğrileri ve zaman incelemesi çalışmaları irdelendiğinde; Kolemanit-1 ve Kolemanit-2 örnekleri için sırasıyla 2 nolu ve 4 nolu rezonans piklerinin radyasyona duyarlı olmaları ve daha kararlı olmaları (zamana bağlı sönüm oranında azalma Kolemanit-1'de %40, Kolemanit-2'de %20) nedenleri ile doz ölçümlerinde kullanılabileceği sonucuna varılmıştır. Üleksit ve İnyoit için ise, sırasıyla 7 nolu ve 8 nolu rezonans piklerinin toplamının (orta pik) dozimetrik özelliğinin fazla olduğu sonucuna ulaşılmıştır. UV ışınlamanın etkisi ile ışınlanmış ve ışınlanmamış Kolemanit-1 ve Kolemanit-2'de spektrumdaki pik şiddetlerinde anlamlı bir fark olmamıştır, Üleksit ve İnyoit'de spektrumdaki mangan pik şiddetlerinde artış olmuştur. Tez kapsamında; incelenen örneklerin dozimetrik özelliklerinin belirlenmesi amacıyla kullanılan ESR ölçümlerine tamamlayıcı bilgiler verebilmesi amacıyla Termolüminesans (TL) çalışmaları da cGy, Gy ve kGy mertebelerinde ışınlanan örnekler için yürütülmüştür. Gerçekleştirilen TL çalışmaları, ışınlanmış ve ışınlanmamış doğal Bor minerallerinde anlamlı bir farkın olmadığını göstermiştir.
Doğal kauçuk/bütadien kauçuk esaslı elastomerik malzemelerin hazırlanması, karakterizasyonu ve raylı sistem araçlarında birincil süspansiyon titreşim sönümleme elemanı olarak kullanımının incelenmesi
Bu tezin amacı doğal kauçuk ve bütadien kauçuk kullanılarak farklı oranda ve farklı türde karbon siyahları ile hamur sistemlerinin hazırlanması, hazırlanan bu karışımların pişme özelliklerinin incelenmesi ve karakterizasyonun yapılması, karbon siyahının elastomer özelliklerine etkisinin değerlendirilmesi ve hazırlanan karışımların raylı sistem araçlarında birincil süspansiyon olarak kullanılan elastomer esaslı konik yaylarda kullanımının incelenmesidir. Tez kapsamında dört farklı reçete oluşturulmuştur. Reçetelerde doğal kauçuk bütadien kauçuk oranı sabit tutulmuş dolgu maddesi karbon siyahının oranı ve türü değiştirilmiştir. Hazırlanan kauçuk karışımların önce Hareketli Kalıp Reometresinde (MDR) cihazında pişme davranışları incelenmiştir. Pişme özelliklerine göre belirlenen sıcaklık ve sürede hidrolik preste test plakaları üretilmiştir. Hazırlanan test plakaları üzerinden sertlik, kalıcı deformasyon, mekanik testler ve ısıl yaşlandırma testleri yapılmıştır. Kauçuk karışımlarında kullanılan karbon siyahlarının türünün etkisinin değerlendirilmesi ve diğer dinamik mekanik özelliklerinin değerlendirilmesi amacı ile Kauçuk Proses Analizör (RPA) cihazı yardımı ile karışımların farklı frekanslarda depo modül değerleri ve çapraz bağ yoğunlukları bulunmuştur. Karbon siyahının depo modülü üzerindeki etkisini gözlemek amacıyla ayrıca farklı frekanslarda DMA cihazıyla da frekans taraması yapılmıştır. DMA cihazı ile karışımların sönümleme özellikleri de belirlenmiştir. Ayrıca disklerin konik yay ürününde kullanımını değerlendirebilmek için Elastomer Test Sistemi cihazı ile yük altında, farklı frekanslarda tarama yapılarak karışımların sönümleme, doğal frekans, titreşim geçirgenliği ve direngenlikleri değerlendirilmiştir. Elde edilen veriler ışığında karışımlar arasından seçilen NR50 formülü ile elastomer esaslı konik yay hazırlanarak, konik yay için tanımlanan şartname değerlerine uygunluğu ve araçta kullanılabilirliğini incelemek amacı ile elastomer esaslı konik yaya; kalıcı deformasyon, dikey – yanal yük altında yer değiştirme (direngenlik) testleri yapılmıştır. Yapılan çalışmalar ışığında, geliştirilen karışımların elastomer esaslı konik yayda kullanılabileceği kanıtlanmıştır.
Moleküler baskılı floresannanoparçacıkların sentezlenmesi ve sensörsistemlerinde kullanımlarının incelenmesi
Son yıllarda üstün floresans özellikleri, fotokimyasal kararlılıkları ve farklı uygulama alanlarında kullanım kabiliyetleri lantanit (nadir toprak elementi) katkılı üst enerji dönüşümü yapabilen nanoparçacıkların (upconversion nanoparticles - UCNP) farklı birçok alanda ilgi çekmesine ve sıkça kullanılan kuantum dot ve organik boyalara kıyasla tercih edilmesine sebep olmuştur. UCNP yapıları, gün ışığında çıplak gözle görülebilecek şiddetli ışıma yapmaları, toksik olmamaları, yüksek foto kararlılık göstermeleri ve biyouyumlu olmaları gibi nedenlerle tıbbı görüntüleme, tedavi, ilaç salımı, adli bilimler gibi alanlarda sıklıkla kullanılmaktadırlar. Farklı geometri ve boyutlarda sentezlenebilen bu yapıların birçok sensör uygulamasında da başarılı bir şekilde kullanılabildiği görülmektedir. Bu tez çalışmasında, β– fazına sahip iterbiyum (Yb) ve erbiyum (Er) katkılı sodyum itriyum florür (NaYF4) matrisi (β–NaYF4:Yb3+, Er3+) UCNP yapısı olarak sentezlenmiştir. Azoik bir boyar madde olan basic red 9 (BR9) molekülü, model bir bileşik olarak seçilmiş ve bu bileşiğe özgü moleküler baskılı polimer (MBP) ile UCNP yüzeyi modifiye edilmiş ve UCNP temelli floresan bir sensör sistemi geliştirilmiştir. Tez kapsamında UCNP'lerin farklı hidrotermal yöntemler ile sentezleme süreci optimize edilmiş, en uygun sentez yöntemi belirlenmiş ve elde edilen bu nano yapıların karakterizasyonları gerçekleştirilmiştir. Sentezlenen UCNP'lerin yüzeyleri, 3 farklı yöntem ile MBP tabakası ile kaplanmış ve en uygun modifikasyon yöntemi tespit edilmiştir. Belirlenen en uygun yöntem kapsamında, UCNP yüzeyi önce tetraetilortosilikat (TEOS) ile ardından trietoksivinil silan (TEVS) ile modifiye edilmiş ve yüzeylere vinil grupları kazandırılmıştır. Bir sonraki adımda UCNP'lerin BR9 baskılı polimerik yapı ile kaplanması için monomer ve hedef molekül arasında oluşan kompleks kararlılığının spektroskopik yöntemler ile değerlendirilmesi ve tersinir katılmaayrılma zincir transfer (RAFT) polimerizasyonu tekniği ile moleküler baskılı polimer tabakanın UCNP etrafında oluşturulması çalışmaları yürütülmüştür. Elde edilen yapıların morfolojik özellikleri ve kimyasal yapıları fourier dönüşüm spektroskopisi-attenuated total relectance (ATR-FTIR), (aramalı elektron spektoroskopisi (SEM), taramalı elektron spektoroskopisi-enerji dağıtıcı X-ray (SEM-EDX), X ışınları fotoelektron spektroskopisi (XPS), X-ray defraktometresi (XRD) gibi deneysel tekniklerle aydınlatılmıştır. Karakterizasyonları tamamlanan moleküler baskılanmış polimer ile kaplanmış UCNP yapılarının (MBP@UCNP) hedef molekül olan BR9'a karşı bağlanma, tanıyıcılık ve seçicilik performansları değerlendirilmiştir. MBP@UCNP yapılarının yüksek bağlanma kapasitesi ve tekrar kullanılabilirlik gösterdikleri ve diğer boyar maddelere oranla azoik hedef moleküle karşı tanıyıcılık ve seçimlilik sergiledikleri tespit edilmiştir. MBP@UCNP yapılarının en düşük tespit limiti (LOD) değeri 0.7 ppb bulunmuştur ki bu değer literatürle kıyaslandığında oldukça düşüktür. Geliştirilen sensör sisteminin performansı gerçek su numuneleri ile yapılan bağlanma çalışmaları ile de test edilmiştir. Yürütülen çalışmalar neticesinde, model olarak seçilen BR9 varlığında uygulanan yöntemin oldukça başarılı sonuçlar verdiği görülmüştür. Bu durum, farklı hedef moleküllere özgü sensör sistemlerinin benzer deneysel tekniklerle geliştirilebileceğine yönelik önemli bir potansiyel arz etmektedir.
Yarı iletken polimerlerin bant aralıklarının ve osilatör güçlerinin kuantum mekaniksel yöntemlerle araştırılması
Son yıllarda iletkenliklerinin keşfedilmesiyle beraber polimerler birçok uygulamada metallerin yerini almaya başlamıştır. Polimerlerin kolay hazırlanmaları, düşük maliyetleri, korozyona karşı dayanıklı olmaları ve hafif olmaları, onları metaller üzerinde avantajlı kılar. Polimerlerin kendisinin doğrudan herhangi bir metal ile birleştirilmeden de iletken olabileceği ilk kez 1950li yıllarda ortaya çıkmıştır ve o zamandan bugüne yapılan çalışmalar polimerlerin iletkenliğini artırmayı hedeflemektedir. İletken polimerlerin kullanım alanlarına örnek olarak organik güneş pilleri, elektronik devreler, organik ışık yayan diyotları, aktüatörler, kimyasal ve biyo-sensörler gösterilebilir. Polimerlerde iletkenlik bant aralığı teorisi yardımıyla ii açıklanır. Eğer enerji düzeyinde valans bandı ile iletkenlik bandı arasında 9 eV veya daha fazla potansiyel farkı varsa bu polimer yalıtkandır. Bu potansiyel farkı 0,1 ile 4 eV arasında değişiyorsa bu polimerin yarı iletken olduğunun işaretidir. İletken polimerlerde ise valans bandı ile iletkenlik bandı iç içe geçmiş durumdadır. Polimerlerin iletkenlik özellikleri hem deneysel hem de teorik yollarla çalışılabilmektedir. Deneysel tekniklerde güvenilir sonuçlar elde edilmesine karşın, laboratuvar ortamında yapılan sentezleme ve ayrıştırma işlemleri sebebiyle zamana ihtiyaç duyulmaktadır, fakat teorik çalışmalarla bu işlemlere gerek kalmadan yalnızca bilgisayarlar ve gelişmiş yazılımlar sayesinde polimerlerle ilgili birçok bilgi kolaylıkla elde edilebilmektedir. Teorik çalışmaların önemli bir kolu olan kuantum mekaniksel yöntemler Yarı deneysel (Semi-Empirical), Ab Initio ve Yoğunluk Fonksiyoneli Teorisi (DFT) olarak sıralanabilir. Bu çalışmada poliasetilen (trans ve cis yapılı), politiyofen, poli(p-fenilen) ve poli(p-fenilen vinilen)'in Ab Initio tekniklerinden olan tekli uyarılmış konfigürasyon etkileşimi yöntemi (CIS) yoğunluk fit edilmesi tekniği (DF) kullanılarak bant aralıkları ve osilatör güçleri değerleri hesaplanmıştır. Aynı polimerlerin bu değerleri bir de TD-DFT (zamana bağlı yoğunluk fonksiyonel teorisi) tekniğiyle elde edildikten sonra her iki yöntem hem birbiriyle hem de literatürdeki deneysel verilerle kıyaslanmıştır. Elde edilen sonuçlar göstermektedir ki, TD-DFT tekniğiyle elde edilen bant aralığı değerleri deneysel verilere çok yakınken, CIS metodu ile hesaplanan değerler hem TD-DFT değerlerinden hem de deneysel sonuçlardan belirli bir miktar yüksektir.
Demattia-esnek çatlama test cihazının tasarımı ve elastomerler testlerinde kullanılması
Bu tez kapsamında geliştirilen Demattia-Esnek Çatlama test cihazı elastomerlerin dinamik koşullarda çatlamaya karşı dayanımlarının test edilmesi amacıyla kullanılan ve ülkemizde henüz üretilmeyen ve tamamen ithal edilen bir cihazdır. Cihazın uluslararası standartlara uygun olması için ve standartlara uygun tasarım yapılabilmesi için çalışmanın ilk bölümünde gerekli standartlar incelenmiştir. Ayrıca, farklı marka muadil ürünler de incelenmiş, kullanıcı yorumları alınmıştır. Bu sayede tasarım aşaması için gerekli bilgiler derlenmiştir. Bunun yanında dinamik yorulmaya sebep olan nedenler literatürden taranarak teze eklenmiştir. Çalışmanın ikinci bölümünde test cihazı için kavramsal tasarımlar hazırlanmış, bunların içerisinde detay tasarıma geçilecek kısımlar belirlenmiş ve detay tasarım aşamasında mekanik ve elektronik tasarım sonuçlandırılmıştır. Bu sonuçlara göre hazır ürünlerin seçimleri yapılmıştır. Bu çıktılarla beraber mekanik üretim dokümanları ve ürün listesi hazırlanmıştır. Hazırlanan cihaz için Aktaş Grup Hava Süspansiyon Sistemleri, Ltd. Şti. ve Babacan Endüstri ve Kauçuk Ürünleri İmalatı San. Tic. Ltd. Şti'nden temin edilen numuneler geliştirilen test cihazı ile test edilmiştir. Belirlenen esnek çatlama test süreleri bu test numunelerini üreten firmaların test laboratuvarlarında elde edilen sonuçlarla karşılaştırılmıştır. Tüm örnekler için aynı sonuçlar elde edilmiştir. Ömür testleri başarıyla tamamlanmış, güvenilir, kullanıcı ihtiyaçlarına uygun ilk yerli ve milli bir esnek çatlama test sistemi geliştirilmiştir.
Geri sekme esnekliği ölçüm cihazı tasarımı ve elastomer testlerinde kullanılması
Geri sekme esnekliği ölçüm cihazı elastomerlerin esnekliğinin belirlenmesi amacıyla kullanılan ve ülkemizde üretilmeyen, ithal edilen bir cihazdır. Tasarıma başlanmadan önce referans alınacak standartlar belirlenerek incelenmiş ve cihazın sahip olması gereken özellikler listelenmiştir. Bu bilgiler kullanılarak cihazın detaylı tasarımı yapılmış, kullanılacak hazır ürünler belirlenmiştir. Tasarlanan geri sekme ölçüm cihazının parçalarının uygun teknikler ile üretilmesinin ardından cihaz montajlanarak çalışır hale getirilmiştir. Daha sonra cihazın çalışmasının doğrulanması için standart test yöntemlerinde belirtilen sürtünme ve sarkaç periyoduna bağlı indirgenmiş sarkaç boyu hesaplanmıştır. Bunun yanı sıra Ferkan A.Ş. ve Standart Profil A.Ş. firmalarında farklı cihazlar ile ölçülerek geri sekme esneklik değeri belirlenen numuneler ile karşılaştırmalı ölçümler yapılmıştır. Elde edilen sonuçlar gereksinimi karşılamadığı için tasarım değişlikleri yapılmıştır ve cihaz gereksinimleri sağlayacak şekilde revize edilmiştir. Yapılan güncelleme sonrasında doğrulama testleri ve karşılaştırmalı ölçümler tekrarlanarak cihazın doğruluğu kontrol edilmiştir. Doğrulama için kullanılan numunelerden farklı olarak doğal kauçuk temelli 4 tane farklı reçetede hamur hazırlanmıştır. NR 50 ve NR 60 kodlu reçeteler arasında FEF 550 karbon siyahı oranı arttırılmıştır. NR-MT 50 ve NR-MT 60 kodlu reçetelerde ise FEF 550 oranı sırası ile NR50 ve NR60 reçeteleri ile aynı tutulmuş ve ek olarak aynı oranda MT 990 eklenmiştir. Hazırlanan numunelerin üretilen cihazda geri sekme esneklik değerleri ölçülmüştür. Yapılan ölçüm sonucunda, NR 50 reçeteli numunenin %71, NR-MT 50 reçeteli numunenin %74, NR 60 reçeteli numunenin %52, ve NR-MT 60 reçeteli numunenin %70 geri sekme esnekliği olduğu görülmüştür. 50 shore A sertlikteki NR içine MT 990'ın eklenmesi sertliğini değiştirmediği gibi geri sekme değerini de değiştirmemiştir. 60 sertlikte FEF 550 ve HAF 330 kullanılarak hazırlanan NR için elde edilen %53 geri sekme esnekliği değerinin MT 990 eklenmesiyle hızla %70 düzeyine çıktığı görülmüştür. Bu durumda geri sekme davranışının elastomerin hazırlanmasında kullanılan karbon siyahının tipine ve elastomerin shore A sertliğine bağlı olarak değişim gösterebileceği ancak sistematik ilişkinin kurulabilmesi için daha farklı karbon siyahı oranları ve sertlik değerleri ile çalışılması gerektiği sonucuna varılmıştır.
Arsenik iyonlarının adsorpsiyonunda kullanılan poli(1-vinilimidazol) aşılanmış polimerik adsorbent hazırlanması
Bu tez çalışmasında, tersiyer amin fonksiyonel gruplara sahip yeni polistiren esaslı anyon değiştirici (PS-VIM) adsorbent malzeme, 1-vinilimidazolün klorometil polistiren polimerik partiküller üzerine ATRP aşı polimerizasyonu reaksiyonu ile sentezlenmiştir. 1-vinilimidazol monomerinin klorometil polistiren polimerik partiküller üzerine aşılanma derecesi %83,65 olarak bulunmuştur. Polimerik adsorbent malzemenin yapısal ve morfolojik özellikleri FTIR, SEM ve EDX kullanılarak analiz edilmiştir. 1-vinilimidazol aşılanmış polistiren esaslı polimerik partiküllerin As(V) adsorpsiyon özellikleri incelenmiştir. Çözelti pH'ı, temas süresi, As(V) başlangıç derişimi, iyonik şiddet ve girişim yapan anyonların adsorpsiyon üzerindeki etkileri kesikli adsorpsiyon deneyleri ile 25 °C'da incelenmiştir. As(V) iyonlarının adsorpsiyonunun pH'a bağlı olduğu ve maksimum adsorpsiyonun pH 5,00'te gerçekleştiği tespit edilmiştir. Kinetik çalışmalar, As(V) iyonlarının PS-VIM polimerik partiküller üzerine gerçekleşen adsorpsiyon işleminin, yalancı ikinci dereceden reaksiyon modeline (R2=0,9902) uyduğunu göstermiştir. As(V) iyonları için PS-VIM adsorbentinin adsorpsiyon izoterminin Langmuir modeline uyduğu bulunmuştur. As(V) iyonlarının maksimum adsorpsiyon kapasitesi, Langmuir izoterminde pH 5,00'te 90,10 mg/g adsorbent olarak belirlenmiştir. Çözeltinin iyonik şiddetinin NaCl ile artması, As(V) iyonlarının adsorpsiyonunu etkilediğini göstermiştir. Adsorbent ve adsorbat arasındaki etkileşimin, elektrostatik etkileşim olduğu tespit edilmiştir. As(V) iyonlarının adsorpsiyonu, Cl-, NO3-, SO42- ve PO43- gibi girişim yapan iyonların varlığında incelenmiş ve SO42- iyonlarının As(V) iyonlarının adsorpsiyonunu önemli ölçüde etkilediği, ancak Cl- iyonlarının en az etkiye sahip olduğu bulunmuştur. On adsorpsiyon-desorpsiyon döngüsü, polimerik malzemenin, As(V) iyonlarının sulu çözeltiden verimli bir şekilde uzaklaştırılması için uygun olduğunu göstermiştir. Adsorbent olarak kullanılan PS-VIM polimerik partiküllerinin yüksek derişimlerde As(V) iyonları içeren çeşme sularından arsenik iyonlarını uzaklaştırdığı gösterilmiştir. Bu tez çalışmasında elde edilen sonuçlardan, PS-VIM polimerik partiküllerin As(V) iyonlarının sulu çözeltilerden uzaklaştırılması için etkili bir adsorbent malzeme olarak kullanılabileceği sonucuna varılmıştır.
Silikon elastomerlerin sönümleme özelliğini kontrol eden yapısal parametrelerin belirlenmesi
Silikon kauçuklar günümüzde endüstride geniş bir kullanım alanına sahiptir. Diğer kauçuk türlerine göre birçok avantajı vardır. Bunlardan başlıcaları; yüksek ve düşük sıcaklıklarda özelliklerinin değişmemesi, iklim koşullarından etkilenmemesi, çok yüksek yalıtım özelliği göstermesidir. Bu ve bunun gibi birçok avantajından dolayı günümüzde elektrik-elektronik sektörü, otomotiv sektörü, gıda, tıp ve inşaat sektöründe sıklıkla kullanılmaktadır. Ses, basınç dalgalanmaları tarafından yaratılan bir olgudur. Ancak sürekli ses makinelerde enerjinin boşa harcanmasına neden olmaktadır. Silikon elastomerler de yüksek sönümleme kapasitesine sahip olmasından dolayı makinelerde boşa harcanan enerjinin engellemesinde oldukça önemli bir yere sahiptir. Bu tezde silikon elastomerlerin enerji sönümleme özelliklerini kontrol eden yapısal parametrelerin belirlenilmesine çalışılmıştır. İlk olarak farklı kaynaklardan elde edilen silikon tipleri kullanılarak karışımlar hazırlanmıştır. Hareketli Kalıp Reometresinde (MDR) 180 oC ve 20 dakika süresince karışımların pişme özellikleri incelenmiştir. MDR cihazındaki sonuçlardan en yüksek delta tork değeri Silplus 80 silikonunda elde edilmiştir. R752/50 ise en düşük delta tork değerine sahiptir. Kopma uzama eğrileri incelendiğinde en fazla uzamanın R752/50 silikon elastomer örneğine ait olduğu görülmüştür. Silplus 80 ve Ravasil 70 örneklerinde en az uzama değeri elde edilmiştir. Çapraz bağ yoğunluğu Kauçuk Proses Analizörü (RPA) cihazında frekans taraması yapılarak belirlenmiştir. En yüksek çapraz bağ yoğunluğuna sahip olan örnek Silplus 80 silikon elastomerinde elde edilmiştir en düşük çapraz bağ yoğunluğuna sahip olan elastomer R752/50'dir. Pişmiş ve pişmemiş örneklerde gerinim taraması yapmak için frekans 1,0 Hz'de sabit tutulurken, 50 oC'da gerinim taraması yapılmıştır. Gerinim aralıkları ise 0,007-12,942 o'dir. Strain (gerinim) taraması malzemedeki Payne etkisini görmek amacıyla yapılmıştır. En büyük delta G' değerleri arasındaki fark Silplus 70 örneğinde görülmüştür. En düşük G' değerleri arasındaki fark R752/50 örneğine aittir. G' değerinin küçük olması da daha düşük Payne etkisi, daha güçlü dolgu maddesi-polimer etkileşimi ve daha iyi dolgu maddesi dağılımı anlamına gelmektedir. Termal Gravimetrik Analiz (TGA) sonuçlarına baktığımızda en yüksek bozulma sıcaklığı Ravasil 70 örneğine ait olup sıcaklık değeri de 606,0 oC'dir. En düşük bozulma sıcaklığı R752/50 örneğimize ait olup 532,5 oC'dir. Silikon elastomerlerin bu temel karakterizasyon çalışmalarından sonra enerji sönümleme özellikleri incelenmiştir. Bu amaçla, Sıcak pres kullanılarak disk şeklinde örnekler hazırlanmıştır. Hazırlanan disklere Evrensel Test Cihazı kullanılarak tek yönlü %10,%20,%30, %40 ve %50 oranlarda 10 döngülü sıkıştırma testi yapılmıştır. Sıkıştırma testi verilerinden yararlanılarak birim hacim başına absorplanan enerji değerleri bulunmuştur. Hareketli kalıp reometresinde de en yüksek delta tork değerine sahip olan Silplus 80'in en yüksek absorplanan enerji değerine sahip olduğu görülmüştür. Bu çalışmaların sonunda enerji sönümleme özellikleri ile silikonun sertlik ve çapraz bağ yoğunluğu gibi yapısal parametreleri ile enerji sönümleme özellikleri arasında bir ilişkinin olduğu görülmüştür. Çapraz bağ yoğunluğu artırılarak enerji sönümleme özelliğinin artırılacağına varılmıştır. Anahtar Kelimeler: Silikon elastomer, sönümleme, payne etkisi, çapraz bağ yoğunluğu, reoloji
Hacimsel iskelet kası hasarları için polimer bazlı destek malzemelerin geliştirilmesi
Önemli bir sosyal ve ekonomik yükü oluşturan hacimsel kas kayıpları her yıl milyonlarca insanı kazalar, savaşlar ve tümör operasyonları sebepleri ile etkilemektedir. İskelet kası yapısı doğal onarım mekanizmasına sahip olmasına rağmen, kritik seviyenin üzerindeki kayıplarda kendi kendine iyileşmeyi sağlayamamaktadır. Bu durum ciddi oranda fonksiyonel hasarlar ve estetik eksikliklerle sebep olmaktadır. İskelet kası doku mühendisliği yaklaşımlarında hacimsel kas kaybını desteklemek ve hücresel davranışları yönlendirmek için fonksiyonel doku iskelesi tasarımlarına odaklanılmıştır. Bu tez çalışmasında, hacimsel iskelet kası hasarları için polimer bazlı destek malzemelerin geliştirilmesi amaçlanmıştır. Bu amaç için doğal kas dokusunu taklit edebilmek amacıyla hizalanmış, hücresel gelişimi ve yönelimi destekleyecek seviyede elektriksel aktiviteye sahip poli(ε-kaprolakton) (PCL) bazlı fiber iskeleler hazırlanmıştır. Fiber iskelelerin üretimi için bilgisayar destekli Döngüsel Islak Eğirme Düzeneği (DIED) geliştirilmiştir. İletken özelliğe sahip gümüş nanoteller (AgNT) ile katkılanmış PCL-AgNT kompozit fiberler yüksek verim ile üretilmiştir. DIED üretim parametrelerinin; PCL molekül ağırlığı, çözücü sistemi, çöktürme banyosu sıcaklığı, PCL ve AgNT derişimleri vb. optimizasyonu gerçekleştirilmiştir. Fiberlerin kimyasal, morfolojik, ısıl özellikleri ve biyobozunma davranışları karakterize edilmiştir. C2C12 fare myoblast iskelet kası hücrelerinin elektriksel uyarım altında ve elektriksel uyarım uygulanmadan PCL ve PCL-AgNT kompozit fiber iskeleler üzerindeki çoğalma davranışları ve morfolojileri incelenmiştir. Hücre kültür çalışmalarının 7. gününde, 1.5 V ile 3 V elektriksel uyarım gerilimi altında PCL-AgNT kompozit fiber iskele yüzeylerinde PCL fiberler göre daha fazla hücre çoğalması ve canlılığı gözlenmiştir. Tez çalışması kapsamında DIED ile antibakteriyel özelliğe sahip kompozit fiber formülasyonları geliştirilmiştir. Antibakteriyel ilaç etken madde sülfatiyazol - AgNT kompleksi hazırlanmış ve kompozit fiber üretimi DIED ile gerçekleştirilmiştir. Sülfatiyazol - AgNT yüklü fiberlerin antibakteriyel özellikleri disk difüzyon testi ile 4 farklı bakteri türü için incelenmiş, yüksek başarı elde edilen bakteri türleri ile erken aşama bakteriyel tutunma çalışmaları gerçekleştirilmiştir. Sonuç olarak, PCL-AgNT kompozit fiberler ve antibakteriyel formları iskelet kası doku destek malzemeleri adayı olarak başarılı ve umut vaat edici özellikler sunmuştur.
Stronsiyum-nano zeolit A ile desenlenmiş üç boyut baskılı poli(laktik asit) kemik doku iskelelerinin geliştirilmesi
Kemik hasarlarında polimer bazlı destek malzemelerin kullanımı artan bir hızda devam etmektedir. Polimerlerin biyouyumlu, biyobozunur özelliklerinin olmasının yanı sıra 3B yazıcılarda kullanılabilmeleri sayesinde kişiye özel bir üretim yapılabilmesi bu artışın sebepleri arasında verilebilir. Bu tez çalışmasında üç boyutlu (3B) yazıcıda fused deposition modeling (FDM) teknolojisi kullanılarak poli(laktik asit) (PLA) bazlı destek malzemelerin üretilmesi ve yüzey modifikasyonu ile kemik hasarlarında kullanılmak üzere geliştirilmeleri amaçlanmıştır. 3B yazıcıda basılıcak olan malzeme SolidWorks programında çizilmiş, daha sonra 3B yazıcıda 180 oC'de nozzle ucunun sıcaklığında basım gerçekleştirilmiştir. 3B yazıcıda basım için PLA'nın seçilmesinin sebebi biyouyumlu ve FDA onaylı bir polimer olmasıdır. Ayrıca PLA kemik rejenerasyonu için uygun mekanik özelliklere ve biyobozunma süresine sahiptir. 3B basım öncesi ve sonrası PLA'nın kimyasal ve ısıl özellikleri sırasıyla FTIR ve DSC ile karakterize edilmiştir. İkinci aşama olarak üretilen PLA kemik destek malzemelerin yüzey modifikasyonunda kullanılacak olan nano ve mikro zeolit A tozlarının sentezleri gerçekleştirilmiştir. Sentezlenen nano zeolit A tozlarının boyutları 150-250 nm arasında değişiklik gösterirken, mikro zeolit A tozları 1-1.5 μm boyutlarındadır. Nano ve mikro zeolit A tozlarının karakteristik pikleri XRD ile konfirme edilmiştir. Kemik yapısında bulunan en önemli elementlerden biri olan stronsiyum (Sr) iyon değişimi yöntemi ile zeolit A yapılarına yüklenmiştir. Sr yüklenen Zeolit A yapıları EDX ve XRD ile karakterize edilmiştir. 3B basılmış PLA malzemelerinin zeolitler ile yüzey modifikasyonu için üç farklı yöntem uygulanmıştır. Bu yöntemler sonunda ortaya çıkan ürünlerin kimyasal, ısıl ve morfolojik özellikleri incelenmiştir. Katman biriktirme tekniği ile yüzeyi nano ve mikro zeolit A, Sr yüklü nano ve mikro zeolit A ile dekore edilen PLA kemik destek malzemelerinin biyobozunma ve hücre kültür performansları değerlendirilmiştir. Zeolitler ile yüzey dekorasyonu PLA yüzeylerinde hidrofilik karakterin ve serbest yüzey enerjisinin artmasına sebep olmuştur. Saos hücreleri 14. gün sonunda zeolit modifiye edilmiş PLA yüzeylerinde, kontrol PLA'a göre daha fazla Alkalen Fosfataz (ALP) aktivitesi göstermişlerdir. Tez çalışmasında Sr yüklü zeolit A ile yüzeyi modifiye edilmiş PLA yapılarının kemik doku iskelesi olarak kullanılması yönünden olumlu ve umut verici bulgular elde edilmiştir.
Silikon elastomerlerin ömür süresine etki eden parametrelerin belirlenmesi
Silikon kauçuklar sentetik kauçuk grubuna aittir. Hava şartlarına karşı yüksek direnç, iyi elektriksel özellikler, geniş sıcaklık aralığında çalışma ve kolay işlenebilirliği gibi birçok kullanım avantajı mevcuttur [1]. Bu özelliklerinden dolayı, dış mekan yalıtım uygulamaları ve elektrik iletim ve dağıtım sistemleri gibi uygulamalarda sıklıkla kullanılmaktadır Mükemmel özellik ve dayanıklıklarına rağmen silikon kauçuklar çeşitli çevresel ve kimyasal etkenlere ve yüksek sıcaklara maruz kaldığında zamanla bozunmaya maruz kalırlar Bu bozunma ''yaşlanma '' olarak adlandırılmaktadır. Yaşlanma bir malzemenin istenilen özelliklerinin bozunması sonucunda oluşmaktadır Yaşlanmanın malzeme özellikleri üzerindeki etkilerini anlamak için ömür tahmini yapılmaktadır. Ömür tahmini malzemeyi iyileştirme açısından önem kazanmaktadır
Sıcaklık taramalı gerilim gevşemesi (TSSR) yöntemi ile vinil metil silikon (VMQ) elastomerinin çapraz bağ yoğunluğunun belirlenmesini sınırlayan koşullar
Bu çalışmanın temel amacı, farklı sertliklerde vinil metil silikon (VMQ) elastomerlerin durulma davranışlarının sıcaklık taramalı gerilme durulma (TSSR) cihazında belirlenmesi ve bu cihaz ile çapraz bağ yoğunluğunun bulunmasını sınırlayan koşulların incelenmesidir. Daha önce TSSR cihazı ile 50, 60, 70 Shore A gibi farklı sertliklerde vinil metil silikon elastomerleri ile yapılan çalışmalarda çapraz bağ yoğunluklarının hesaplanamadığı görülmüştür. Bu zamana kadar bu polimerler ile ÇBY değerinin neden gözlenemediği, bunu sınırlandıran koşulların neden olduğu yaklaşımından yola çıkılarak bu çalışma yapılmıştır. Sertliğin, buna bağlı olarak moleküler kütlenin silikon elastomerlerin durulma özelliklerinin üzerindeki etkisini incelemek amacıyla 10 Shore A sertlikten 60 Shore A sertliğe kadar VMQ ile karışımlar hazırlanmıştır. VMQ karışımlarının kürleşme özelliklerinin ve çapraz bağ etkinliğinin karşılaştırılması amacıyla TAIC (trialil izosiyarünat) ve ZDA (çinko akrilat) gibi farklı hızlandırıcı ko-ajanlar kullanılarak karışımlar oluşturulmuş farklı metotlar ile çapraz bağ yoğunlukları hesaplanmıştır. Farklı sertliklerde ve farklı yardımcı ko-ajanlar kullanılarak hazırlanan karışımların kür karakteristiklerinin incelenmesi ve optimum kürleşme koşullarının belirlenmesi amacıyla Hareketli Kalıp Reometresi (MDR) kullanılmıştır. Farklı sertliklerde minimum tork (ML) ve maksimum tork (MH) değerleri incelenip kürleşme dereceleri belirlenmiştir. Aynı sertlikteki silikonlar için TAIC ve ZDA içeren karışımların karşılaştırması yapılmış, ko-ajanların kürleşme özelliklerine etkisi incelenmiştir. Reolojik özellikleri göz önünde bulundurularak test numuneleri oluşturulup TSSR cihazında gevşeme (durulma) özellikleri test edilmiştir. Testin ilk aşaması olan izotermal gevşeme aşaması için karışımların 23 °C'de 2 saat boyunca gevşeme davranışları incelenmiştir. Testin ikinci aşaması olan izotermal olmayan gevşeme aşamasında ise karışımların sıcaklık ile gevşeme davranışları incelenmiş, cihazdan elde edilen çapraz bağ yoğunluğu (ÇBY) değerleri değerlendirilmiştir. Cihazdan elde edilen çapraz bağ yoğunluğu değerlerine ek olarak, izotermal olmayan durulma eğrilerinin eğimleri harici bir yazılım ile bulunmuş ve lastiki-elastiklik eşitlikleri yardımıyla ÇBY değerleri hesaplanmıştır ve cihazdan elde edilen değerler ile karşılaştırması yapılmıştır. Elde edilen ÇBY değerlerinin doğrulamasını yapmak amacıyla kauçuk proses analizörü (RPA) ile frekans taraması çalışmaları yapılmış ve çapraz bağ yoğunluğu değerleri hesaplanmıştır. Yapılan çalışmalar sonucunda elde edilen veriler ışığında TSSR cihazından ÇBY elde edilemediği durumlar incelenmiştir ve olası sebepleri irdelenmiştir. Tüm bu çalışmaların sonucunda artan ÇBY ile gerdirilmiş VMQ elastomerlerin yüksek oranda gerilmeye tepki olarak daha yüksek gevşeme, izotermal durulma ve gerilme miktarlarına sahip olduğu görülmüştür. İzotermal olmayan testlerde ise sertlik arttıkça gerilim bölgesindeki ilk artış eğiminde bir azalma yaşandığı görülmüştür. İçerdikleri fonksiyonel vinil grubu sayısına bağlı olarak, ZDA içeren elastomerlerin ÇBY değerleri TAIC içerenler ile kıyaslandığında TAIC içeren sistemlerin daha yüksek ÇBY değerine sahip olduğu görülmüştür. Çalışmalar aynı zamanda ÇBY değerinin silikonların TSSR uygulamaları için kritik bir parametre olduğunu göstermiştir. RPA yöntemi ile yapılan çalışmalar sonucunda elde edilen çapraz bağ yoğunluğu değerlerinin TSSR yöntemi ile elde edilen değerlere oldukça yakın olduğu belirlenmiştir. Bu da TSSR yönteminin VMQ elastomerler için ÇBY değerinin belirli bir değerin altında kalmak koşuluyla kullanılabileceğini göstermiştir. Anahtar Kelimeler: Çapraz bağ yoğunluğu, Elastomer, TSSR, VMQ
Yüksek sönümleme özelliğine sahip epiklorohidrin esaslı elastomerlerin hazırlanması ve karakterizasyonu
Yüksek sönümleme kapasitesine sahip, farklı polimerik malzemeler titreşimi azaltmak amacıyla endüstride farklı uygulamalarda kullanılmaktadır. Bu malzemelerin çoğunun, sönümleme kapasitesi açısından birçok alanda yetersiz kalmasının yanında yağ, ısı ve kimyasal dayanımlarının düşük olduğu bilinmektedir. Epiklorohidrin (ECH) esaslı ticari olarak Hidrin adı ile bilinen polimerlerin yapısının içerisinde bulunan doymuş uç gruplar ısı, kimyasal ve ozon dayanımının geliştirilmesini ve etilen oksit yapısındaki oksijen polaritesi sayesinde de çok iyi yağ ve yakıt dayanımını sağlar. Bununla birlikte yüksek sönümleme özellikleri sunmaktadır. Bu tez kapsamında yüksek sönümleme özelliğine sahip poli(epiklorohidrin) (ECH yada CO) homopolimeri ve poli(epiklorohidrin-ko-etilen oksit-ko-allil glisidil eter) (GECO) terpolimeri karışımları hazırlanmıştır. Pişirici kimyasal türü, reçine tipi, dolgu miktarı ve homopolimer ve terpolimerlerinin harmanlarının sönümleme davranışı ve fiziksel özelliklere olan etkisi incelenmiştir. Pişirici sistemlerin sönümleme davranışına olan etkisinin araştırılması amacıyla, etilen tiyoüre (ETU) ve Zisnet F-PT marka tritiyosiyanürik asit (TTCA) pişirici kimyasallar olarak kullanılmıştır. Reçine tipinin etkisinin araştırılması amacıyla, C8/C9 aromatik hidrokarbon reçine, C9/C10 aromatik hidrokarbon reçine, fenolik reçine ve sıvı bütadien polimer kullanılmıştır. Dolgu miktarındaki etkiyi incelemek için silan bağlayıcı ajan ile modifiye edilmiş silika 20 phr ve 40 phr oranlarında kullanılmıştır. Harman etkisinin incelenmesi amacıyla epiklorohidrin homopolimer ile epiklorohidrin terpolimerin eşit oranda karıştırılmasıyla sönümleme davranışı araştırılmıştır. Sönümleme davranışlarının incelenmesi amacıyla; sıcaklığa bağlı kayıp faktörü (tanδ) değeri dinamik mekanik analiz cihazı (DMA) ile ölçülmüş olup, geri sekme test cihazı kullanılarak geri sekme testi ve evrensel mekanik test cihazı kullanılarak basma deneyi yapılmış ve enerji sönümleme miktarları değerlendirilmiştir. Hazırlanan elastomerlerin özelliklerinin değerlendirilmesi amacıyla; MDR cihazı ile pişme ve reolojik özellikler, mekanik test cihazı ile çekme testi yapılarak mekanik özellikler, kauçuk proses analizörü (RPA) ile çapraz bağ yoğunluğu ve işlenebilirlik özellikleri ve sertlik test cihazı ile sertlikleri değerlendirilmiştir. TTCA kullanımı ile sönümleme davranışı değişmeden, mekanik özelliklerde büyük ölçüde artış görülmüştür. Fenolik reçine kullanımının, poliepiklorohidrin homopolimeri ve terpolimeri için aktif sönümleme sıcaklık aralığını (tanδ>0,3) arttırdığı görülmüştür. Dolgu miktarındaki artış ile aktif sönümleme aralığı büyük ölçüde değişmemiş olup, mekanik özellikler iyileşerek, işlenebilirliğin zorlaştığı görülmüştür. Poliepiklorohidrin homopolimeri ve terpolimerinin harmanlanması ile sönümleme sıcaklık aralıklarının istenilen sıcaklığa uygun sönümleme seviyesi elde edilecek şekilde ayarlanabileceği kanıtlanmıştır. Yapılan bu çalışma sonucunda, pişirici kimyasal türünün, reçine tipinin, dolgu miktarının ve epiklorohidrin polimer harmanlarının kullanımı ile sönümleme davranışının ECH polimerleri için nasıl kontrol edildiği aydınlatılmıştır.
Peptit ve protein-PEG konjugatlarının sentezi ve kütle spektrometrik analizi
Tedavi edici proteinler farmakoloji alanında oldukça fazla kullanılmalarının yanı sıra, bu alanda tedavi edici protein yapılarını içeren hibrit moleküllerin kullanıldığı birçok klinik uygulama da bulunmaktadır. Polietilen glikol (PEG) kullanılarak, sadece tedavi edici proteinler ile değil tedavi edici diğer bir takım biyomoleküller ve ilaçlarla da pegilasyon adı verilen konjugasyon işlemi gerçekleştirilip hibrit moleküller oluşturulmaktadır. Bu çalışmalarda karşılaşılan en büyük zorluklardan biri, pegilasyon işlemi sonucunda elde edilen moleküllerin analiz edilmeleri, bağlanma bölgelerinin ve bağlanma oranlarının doğru şekilde belirlenebilmesidir. Oluşturulan polimer esaslı bu tedavi edici hibrit moleküllerin analizleri ve karakterizasyonları analitik açıdan oldukça zorlu olmaktadır. Bu tez kapsamında hibrit peptit-polimer ve protein-polimer molekülleri sentezlenerek, bu hibrit moleküllerin analizi ve karakterizasyonları için daha kolay ve zaman almayan analitik yöntemlerin geliştirilmesi amaçlanmıştır. Bu amaç doğrultusunda PEG ile konjugasyona girmesi hedeflenen örnek polipeptit yapıları olarak insan anjiyotensin II ve insan insülini molekülleri kullanılmıştır. Konjugasyon reaksiyonu için farklı molekül ağırlığı dağılımına sahip PEG örnekleri kullanılmıştır. Kullanılan bazı PEG zincirlerinin uç grupları türevlendirilerek farklı reaktif gruplar haline getirilmiştir. Konjugasyon reaksiyonları hem organik çözücü içerikli hem de fizyolojik ortam koşullarında gerçekleştirilmiştir. Son ürün olarak elde edilen hibrit moleküllerin yani konjugatların MALDI-MS sistemi kullanılarak kütle spektrometrik analizleri yapılmıştır. PEG zincirlerinin biyomoleküle bağlanma bölgelerinin ve bağlanma oranlarının direkt belirlenebilmesi amacıyla MALDI-MS/MS yöntemi kullanılmıştır. İnsülinin kullanıldığı büyük yapılı hibrit moleküllerin karakterizasyonu için parçadan-bütüne (bottom-up) proteomik analiz yaklaşımına gidilmiş ve daha sonra MALDI-MS/MS yöntemi ile PEG zincirlerinin bağlanma bölgeleri ve oranları belirlenmiştir. Bu tez çalışması sonucunda, PEG zincirlerinin uç grupları farklı şekillerde modifiye edilebilmiş ve bu PEG zincirleri kullanılarak yapılan konjugasyon reaksiyonlarının başarılı bir şekilde gerçekleştirildiği MALDI-MS yöntemi kullanılarak belirlenmiştir. PEG zincirlerinin biyomolekül üzerindeki bağlanma bölgelerinin yeri ve oranının belirlenmesi, tez kapsamında geliştirilen örnek hazırlama ve MALDI-MS/MS analiz yöntemleri ile pratik ve hızlı bir şekilde gerçekleştirilmiştir.
EPDM elastomerlerinin gerilme durulma davranışlarını kontrol eden parametrelerin belirlenmesi
Bu çalışmanın temel amacı dinamik uygulamalar için yeni nesil EPDM elastomerler kullanılarak yüksek sıcaklıklara karşı performansın arttırılması ve bu EPDM elastomerlere katkı maddelerinin etkisinin aydınlatılmasıdır. Bu amaçla geleneksel EPDM (EPDM-0) ve yeni nesil EPDM (EPDM-A) olarak adlandırılan yüksek molekül ağırlığı ve dar molekül ağırlığı dağılımına sahip yeni nesil EPDM'ler kullanılarak doğal kauçuk (NR60) ile karşılaştırılmıştır. Yeni nesil EPDM'lerin yağ etkisini karşılaştırmak amacı ile EPDM-A,EPDM-A5 (5 phr), EPDM-A10(10 phr), EPDM-A20(20 phr), EPDM-A30 (30 phr) elastomerleri hazırlanmıştır. Kükürt oranının etkisini incelemek için EPDM-AHS yüksek oranda kükürt içeren ve EPDM-ALS yani düşük oranda kükürt içeren karışımlar hazırlanmış ve karşılaştırılmıştır. Tez kapsamında öncelikle hazırlanan elastomerlerin evrensel test cihazıyla kopmadaki uzama ve kopma dayanımları tayin edilmiştir. %100 uzamadaki modül sonuçları incelendiğinde 1,88 MPa ile EPDM-A elastomerinin EPDM-0 ve doğal kauçuktsn hazırlanan NR60 elastomerine göre mekanik özelliklerinin daha iyi olduğu görülmüştür. Tezin ikinci aşamasında sıcaklık taramalı gerilme durulma (TSSR) cihazı ile durulma özellikleri incelenmiştir. TSSR sonuçları değerlendirildiğinde moleküler ağırlık dağılımına bağlı olarak izotermal gevşeme özelliklerinde değişiklikler meydana gelmiştir. Yeni nesil EPDM'lerde yağ içeriği arttıkça %50 gerdirmek için gerekli olan kuvvetin azaldığı izotermal gevşeme oranının da düştüğü görülmüştür. İzotermal olmayan sıcaklık taramalı gerilme durulma deney sonuçları değerlendirildiğinde sıcaklığın artmasıyla gerilim bölgesinde ikinci bir eğri oluşmuş ve bu eğri malzemenin kristallenmesi ile ilişkilendirerek tavlama deneyleri yapılmıştır. Yapılan tavlamaların sonucunda tavlama sayısı arttıkça servis sıcaklığında artış gözlemlenmiştir. Tez çalışmasının son aşamasında evrensel test cihazı kullanılarak sıkıştırma testleri yapılmış, doğal kauçuk ve EPDM elastomerlerin sönümleme özelliklerine bakılmıştır. Sıkıştırma testleri sonucu incelendiğinde EPDM-0 ve NR60 örneklerindeki %10 oranında sıkıştırılması durumunda absorblanan enerji değeri 23 mJ/cm3 değeriyle birbirine çok yakın kalırken EPDM-A'nın %10 basmadaki absorblanan enerji değeri 19 mJ/cm3 olarak EPDM-0 ve NR60'ın absorblanan enerji değerinin altında kalmıştır. Bu sonuçlar EPDM-A'nın dar moleküler ağırlık dağılımına ve yüksek çapraz bağ yoğunluğuna sahip olması ile ilişkilendirilmiştir. Tüm bu yapılan çalışmalar değerlendirildiğinde yeni nesil EPDM'lerin (EPDM-A) mekanik özellikleri artış göstererek dinamik uygulamalarda etkin şekilde kullanılabileceği görülmüştür.
Synthesis of poly(vinylpyrrolidone) (PVP) grafted silica as matrix for generation of palladium nanoparticles and investigation of effect of graft lengths on catalytic activity
The rationale of M.S thesis work is to investigate the effect of chain length of the stabilizing polymer brushes attached to silica surface on the formation of metallic palladium nanoparticles (NPs) and their catalytic activity. Poly(vinyl pyrrolidone) (PVP) brushes forming a very thin shell was grafted from silica microparticles (Si@PVP) via RAFT mediated graft polymerization method thus controlling the molecular weights and structures of PVP grafts. Palladium (Pd) nanoparticles were formed in PVP stabilizing matrix by gamma radiolysis of Pd(Ⅱ) ions to yield Pd(0) decorated core-shell particles (Si@PVP-PdNP). Size Exclusion Chromatography (SEC) and Thermogravimetric Analysis (TGA) results indicated the formation of PVP brushes with different molecular weights on silica. Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) measurements revealed that increased molecular weight of PVP brushes sterically blocked the particle growth and yielded more small Pd nanoparticles rather than fewer large ones. Si@PVP-PdNP having different PVP lengths and Pd sizes were evaluated for their catalytic activity and reusability in the model reduction of 4-nitrophenol to 4-aminophenol. It has been found that longer grafts are more effective in preventing NPs from leaking into the solution through the PVP shell, even if nanoparticles (NPs) are smaller in their presence, yet they allow the diffusion of reactants, resulting in more stable catalytic activity in repeated measurement cycles. On the other hand, short grafts are not sufficiently effective in preventing NP agglomeration and leakage. These findings are particularly important for heterogeneous catalyst systems in that they show the effects of surface-bound polymeric stabilizers on NP formation and catalytic activity.
Kozmetik endüstrisinde kullanılan bazı polimerlerin nano ölçekli yapı özellik ilişkilerinin araştırılması
Bu tez çalışmasında, günlük yaşantımızda sıklıkla kullanılan, yapılarında polimer içeren kozmetik ürünlerinden üç tip sıvı fondöten/krem (QW, LF ve BB krem kodlu örnekler) ile dört tip (farklı özellikleri olan sabitleyici/şekillendirici) saç spreyi üzerine odaklanılmıştır. Öncelikli olarak, kozmetik ürünlerde yaygın kullanılan beş farklı polimer belirlenmiş ve bu polimerlerin arasından (hacimsel) nano ölçekli oluşumlara yol açabilen polimetilsilseskuiokzan, polifenilsilseskuiokzan, feniltrimetikon, C 26-28 alkil dimetikon ve silikon elastomer reçine jel ile çalışmalar başlatılmıştır. Yapılan öncü çalışmalarda, bu polimerlerin nano ölçekli SAXS (Küçük Açı X-Işını Saçılması) analizleri yapısal değişimleri izlemede yol gösterici olmuştur. Saf polimerlerin kozmetik ürünlerde kullanım öncesi, yapı formlarında mevcut olan nano oluşumlarının morfolojileri (şekillenimleri), boyut bilgileri (jirasyon yarıçapları ve maksimum büyüklükleri) ile uzaklık dağılım fonksiyonları elde edilerek, 3B nano oluşumlarının ab-initio yapı modellemeleri yapılmıştır. İncelenen polimerlerden, küresele en yakın şekillenime sahip olan polimetilsilseskuiokzan (PMSQ), nano ölçekli yapı-özellik araştırmaları ile ilgili ayrıntılı çalışmalarda kullanılmak üzere seçilmiştir. Bu polimerin kozmetik kremlerin yapısal özellikleri üzerindeki etkisini incelemek üzere, iki farklı fondötene ve BB kreme farklı polimer katkılarında incelemeler yapabilmek üzere, 343 mg örnek için 0,4; 0,7 ve 1,2 mg (sırası ile % 0,12; 0,20 ve 0,35 kütlece katkı olacak şekilde) PMSQ eklenmiştir. PMSQ'nun diğer polimerlere göre tercih edilmesinin bir başka nedeni de, jel/krem formunda olan kozmetik malzemelerin içinde, bu polimerin makroskopik görüntüyü ve homojen yapıyı bozmayacak şekilde mevcut yapıda çözünerek, miktarının kolayca artırılabilmesi olmuştur. Polimer miktarı artırılarak ve artırılmadan (kontrol grubu olarak) hazırlanan örnekler X-ışını saçılma deseni oluşturmayan alt taşlar üzerine ve deri malzeme üzerine ince film formunda uygulanarak, bu malzemelerin SAXS ve WAXS (Küçük - Geniş Açı X-Işını Saçılması) analizleri yapılmıştır. Elde edilen SAXS (~1-100 nm ölçeğinde) ve WAXS (~1-3 Å ölçeğinde) verileri kullanarak yapısal incelemeler gerçekleştirilmiştir. Ayrıca bu örneklerin SEM ölçümleri de yapılarak, polimer miktarındaki artışının meydana getirdiği yapısal değişiklikler mikroskopik ölçekte de takip edilebilmiştir. Polimer katkılama artışına en iyi yanıtı veren LF kodlu fondöten ile BB krem kullanılarak hazırlanan film formundaki örnekler bu kez 1-4 hafta aralığında yaşlandırılmaya bırakılmış ve örneklerin SAXS analizleri Tayvan Ulusal Sinkrotron Işın Merkezi (NSRRC) de gerçekleştirilmiştir. SAXS analizleri ile elde edilen, nano oluşum uzaklık dağılım fonksiyonlarının, üç boyutlu yapılarda uzun erimlerde homojen dağılımın önemli bir göstergesi olduğu, SEM görüntülerinden elde edilen kısa erimli uzaklık dağılım fonksiyonlarına göre, çok daha doğru ve gerçekçi bulgular içerdiği de yarı-deneysel analizler ile gösterilmiştir. Bu aşamaya kadar yapılan analizlerde polimer artışına en elverişli olan yani, 3B nano morfolojilerin nanokompozit formuna uygun şekil, boyut ve uniform dağılım bilgileri veren, LF kodlu malzemeler olmuştur. Bundan sonraki analizlerde bu örnek üzerine yoğunlaşılarak, yapıları kontrol altına alınan polimer katkısındaki artışın yapı-özellik üzerine etkilerini incelemek üzere, antibakteriyel analizler ve UV soğurucu etkiler incelenmeye başlanmıştır. Sonuçta, film formundaki LF kodlu fondötenin artan PMSQ polimer katkısıyla antibakteriyel özelliklerinin geliştirilebildiği bulgusuna ulaşılmıştır. E.coli ve S.aureus bakterilerine ait artan polimer katkısı ile biyofilm oluşumunun önüne geçilebildiği belirlenmiştir. Ayrıca bu grup için UV optik geçirgenlik ve yansıtma ölçümleri de yapılmış ve 0,4 mg PMSQ katkılama ile elde edilen kozmetik malzemenin UV yansıtma özelliğinin ~% 15 artırıldığı , UV geçirgenlik özelliğinin ise ~% 40'lara kadar azaltılabildiği sonucuna ulaşılmıştır. Aynı örnek grubunun FT-IR analizleri de yapılmış ve PMSQ miktarındaki artış ile moleküller ölçekte yapılarda değişimlerin olup olmadığı da incelenmiştir. İkinci kozmetik ürün grubu olarak, farklı özelliklere sahip dört saç spreyi ile çalışılmıştır. Bu spreyler, 25-35 yaş grubu bayan donörlerden alınan farklı (düz sarı, düz kumral, düz siyah ve kıvırcık kahverengi) formlardaki saç örnekleri üzerine uygulanmış ve yapısal analizler SAXS yöntemi ile başlatılmıştır. Nano oluşum morfolojileri küresele en yakın olan "düz sarı" ve "düz kumral" saç örneklerine moleküler yapı farklılıklarını incelemek üzere FT-IR analizleri de yapılmıştır. Mikroskopik analizler ise SEM (Taramalı Elektron Mikroskopisi) ve EDXS (Enerji Dispersiv X-Işınları Spektroskopisi) yöntemleri ile tamamlanmıştır. Bu grup için elde edilen en önemli bulgu şu şekilde özetlenebilir. Saç spreylerinde kullanılan kimyasal bileşenler, işlevlerini gerçekleştirirken saçın moleküler yapısında çok büyük değişiklik oluşturmamasına rağmen, nanoskopik yapısında (özellikle melanin yapıda) büyük değişikliklere yol açabilmiştir. Bu bulgu, nanoskopik analizlerin kozmetik endüstrisinde mutlaka kullanılması gerekliliğinin bir göstergesidir. Bu tez çalışması ile ilk kez belirlendiği üzere, SAXS analizleri ile elde edilen 3B ab-initio yapı modellemeleri melanin yapıyı izlemede rahatlıkla kullanılabilir. Bu çalışma ile ilk kez SAXS yöntemi ile, saçın yapısında mevcut olan melanin (nanoglobular) formlarının doğal ortamlarında 3B modellemeleri yapılabilmiştir. Kozmetik ürünlerde yaygın olarak kullanılan polimerlerin ve diğer makromoleküler yapıların bir araya gelmesi ile nano ölçekte ortaya çıkan nano oluşumların kendiliğinden (self-assembled) düzenlenmesi ile yapı-özellik ilişkilerinde çok farklı sonuçlar ortaya çıkabilmektedir. Yani kozmetik endüstrisinde nano ölçekte ciddi yapı kontrollerinin yapılması çok yerinde olacaktır. Bu çalışma kapsamında, polimer kullanım oranlarındaki küçük değişikliklerin bile, nanoskopik yapı farklılıklarına yol açtığı, bu nano ölçekli yapısal farklılıkların da antibakteriyel özellikleri geliştirmesi ve UV koruyucu kalkan etkisini artırması gibi, biyofiziksel özelliklerde de etkili olduğu ortaya çıkarılmıştır. Özetle, bu tez çalışması sonucunda, kozmetik endüstrisinde polimer malzemelerin kullanımının optimum oranlarda belirlenmesinin gerekliliği ve yapı-özellik ilişkilerinin moleküler boyuttan başlayarak nano, mikro ve makro boyuta kadar daha ciddi biçimde incelenmesi gerekliliği açıklanmıştır.
Doğal kauçuk esaslı atık lateks eldı̇ven ve polı̇(etı̇len-ko-vı̇nı̇l asetat) kullanılarak yenı̇ termoplastı̇k elastomer kompozı̇tlerı̇n hazırlanması ve sönümleme özellı̇klerı̇nı̇n ı̇ncelenmesı̇
Atık kauçuklar günümüzde ekonomik ve ekolojik açıdan önemli bir sorundur. Bu sorunlar dikkate alındığında geri dönüşüm en iyi seçeneklerden biridir. Atıkları bertaraf etme ve faydalı ürün olarak geri dönüştürme amaçlı birçok çalışma bulunmaktadır. Doğal kauçuklardan elde edilen tek kullanımlık eldiven atıklarının geri dönüştürülmesi de bu çalışmalar arasındadır. Tez kapsamında, üretim fazlası veya hatalı üretim sonucu oluşan doğal kauçuktan üretilmiş lateks eldiven atıklarının yararlı ürün olarak geri kazanımının sağlanması amaçlanmıştır. Toz haline getirilmiş lateks eldivenlerin, termoplastik elastomer olan poli(etilen-ko-vinil asetat) (EVA) ile karıştırılmıştır. Yapılan çalışmalarda öncelikle lateks eldiven tozunun karışım içerisindeki oranı ile mekanik özellikler üzerindeki etkisini incelemek amacıyla 8 farklı oranda EVA-lateks karışımları hazırlanmıştır. Hazırlanan karışımların mekanik ve sönümleme özellikleri incelenmiştir ve EVA miktarının artması mekanik özelliklerin arttığı görülmüştür. Bu tez çalışmasının temel amaçı aslında atık lateks eldiven tozunu karışım içerisinde yüksek oranda tutarak geri kazanımının sağlanmasıdır. Bu nedenle, EVA ile lateks arasındaki uyumluluğu artırmak için maleik anhidrit (MAH) ile aşılama yapılmıştır. Çekme testi sonucunda MAH ile aşılanmış karışımların, aşılanmamış karışımlara göre ile elastik modül, kopma dayanımı ve kopmadaki uzama değerlerinin daha yüksek olduğu görülmüştür. Sıkıştırma çalışmaları sonucunda aşılanmış karışımların absorbe ettiği enerji değerlerinde artış görülmüştür. En yüksek enerji sönemlenmesi MAH aşılanmış % 40 EVA ve % 60 lateks karışımında görülmüştür. Tüm bu deneysel çalışmalar sonucunda maleik anhrit ile aşılanmış EVALAT-g-MAH kompozit sistemlerinin uyumluluğun arttırılması ile mekanik özelliklerin arttığı ve doğal kauçuktan üretilmiş atık lateks eldivenlerin tartan pist plakalsı gibi yararlı ürün olarak geri kazandırabileceği görülmüştür.
Computational and experimental approaches to develop doxycycline imprinted hydrogels for contact lenses
The aim of this thesis is to develop drug delivery hydrogels for contact lens applications which are used as therapeutic agents for cronic diseases such as high eye pressure, cornea neovascularization, eye dryness etc. Contact lenses are optical instruments which are used for elimination of visual defect or cosmetical and therapeutical purposes. Nowadays, contact lenses are made by hydrogel materials which has high water cater content and biocompatibility due to chemical properties. In the studies, newly developed contact lenses are intended to be used for the treatment of ophthalmological diseases. Drug molecules can be loaded to the contact lenses with various methods such as soaking, molecular imprinting or loading to the polymer matrices with colloidal nonoparticles. In this study, doxycycline hyclate molecules are loaded to the hydrogels by soaking and molecular imprinting methods. In this thesis, molecular imprinting method was preferred to synthesize controlled drug released hydrogels. Imprinted polymers which have special cavities belonged to target molecules, are highly selective against to targets. In this study, doxycycline hyclate molecule is choosen as target molecule which is imprinted to the hydrogel matrices. Doxycycline hyclate which is broad spectrum antibiotic, has not been used as template molecule for contact lens applications in literature. In this study, computational methods were used to select suitable monomers for doxycycline imprinted hydrogel synthesis. In molecular simulation step, quantum mechanics, molecular mechanics and molecular dynamic techniques were used. By using quantum mechanics and molecular mechanics, binding interactions between functional monomers and doxycycline molecule were calculated. Quantum mechanics calculations were carried out with Gaussian 09 and SYBYL-X software was used for molecular mechanics studies. Molecular dynamic studies of functional monomer-doxycycline systems were carried with Material Studio 5.0. Also, the effects of crosslinker on prepolymerization step were investigated with molecular dynamic studies. In this step, interactions of crosslinker-doxycycline-functional monomer were studied to simulate experimental conditions. These results were compared with experimental results. In the experimental part, in order to determine crosslinker effect on drug release performance, doxycycline hyclate imprinted and non-imprinted hydrogels were prepared in various crosslinker ratios (1, 1.5, 2, 3 % mole EGDMA). Imprinted and non-imprinted hydrogels were syntesized by free radical polymerization. Acrylic acid was choosen as functional monomer for polymer synthesis. All hydrogels were characterized by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). Also, swelling behaviors of hydrogels were investigated. Doxycycline loading and release performances of both imprinted and non-imprinted hydrogels were investigated. Based on release performances, drug release kinetic profiles were evaluated. According to loading and release performances, doxycycline imprinted hydrogel sample which include 3% mole EGDMA, has higher imprinting factor and more controlled drug release performance compared to other hydrogels.
Effects of polyhedral oligomeric silsesquioxane reinforced polypropylene (PP) nanocomposites on the thermal, mechanical, and optical properties of PP
Polymeric hybrids and nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) - general formula (RSiO1.5)n where R is an organic group – as dispersed inorganic phase offer the opportunity to design advanced materials with enhanced thermal and mechanical performances. The incorporation of POSS or its derivatives into polymers can lead to some improved properties, such as the increase in use temperature, oxidation resistance, surface hardening and mechanical strengths, as well as reductions in flammability, heat evolution, and viscosity during processing. It has been pointed out that the morphology, the thermal stability and tensile properties of thermoplastics (polyolefins, polyesters, polyamides, etc.) containing POSS can be largely affected by the chemical structure, concentration and dispersion degree of POSS nanoparticles. It is possible to obtain dispersion of POSS particles to the scale of individual molecules with size approximately 1-2 nm. In view of this, POSS molecules are nearly equivalent in size to most polymer segments and, therefore, potentially can exert dramatic reinforcement effects. In contrast to other nanofillers, such as layered silicates which are platy and carbon nanotubes which are cylindrical, the shape of the POSS molecules is isotropic. In addition, POSS molecules can be easily functionalized by chemically altering the R groups. This presents opportunities for copolymerization or grafting reactions with functional groups on polymer chains and for defining and controlling the nature of interactions between POSS molecules and the polymer chains. Polypropylene (PP) is a versatile member of polyolefins and this thermoplastic polymer is used in a wide variety of applications including packaging, textiles, stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers and automotive components. PP has been used as the matrix material in a commercial form because of its many attractive properties, such as low weight, relatively low cost, excellent heat distortion temperature (above 100 °C) and its recycling ability. But its toughness, strength and stiffness are not sufficient for applications as an engineering plastic. To reinforce PP, polymer nanocomposite technique by adding rigid polymers, is used. In this study, 1, 3, 5, 8, 10 wt-% POSS containing PP nanocomposites PP/POSS nanocomposites (PP/POSS NC) were prepared by melt blending via extrusion. Methyl-POSS reinforced polypropylene (PP) nanocomposite was used as POSS carrier material (or as a masterbatch) and the effects of methyl-polyhedral oligomeric silsesquioxanes (methyl-POSS) on the rheological, and thermal behavior of polypropylene (PP) were investigated. Rheological studies of PP/POSS NC pellets were operated by using parallel plate rheometry at three different temperatures. For all samples, it can be observed that complex viscosity (η*) decreases with increasing frequency, both storage modulus (G') and loss modulus (G'') progressively increase with increasing frequency. Complex viscosity showed large increase with reduction of temperature at high frequency. The increase of frequency causes the restriction of chain movements and a stiffer behavior was observed. Thermal behaviors of nanocomposites were characterized by DSC and TGA. The fusion enthalpy of the nanocomposites (obtained by peak integration) decreases with increasing of POSS content. 5% and 10% weight loss temperatures obtained from TGA curves. It was observed that increasing of POSS content increased these degredation temperatures and also the thermal stability of nanocomposites. The prepared PP/POSS nanocomposites and PP pellets were also subjected to melt spinning process by using capillary rheometer with 6 take up speed and 3 plunger speed to produce 97 fiber samples. Draw down ratio (DDR=Ddie2/Dfiber2) of fibers were calculated and the effects of draw down ratio on the strength, and polymer chain orientation were investigated by mechanically, optically and morphologically. Mechanical properties of prepared fiber samples measured by universal testing machine. It was observed that POSS composition and DDR of the nanocomposites had a pronounced effect on the tensile properties of these materials. Tensile data shows that the modulus increase with increasing of take up speed and decreasing by increasing of POSS content. Addionally, the maximum load, tensile strain at maximum load, and tensile strain at break decreases with increasing of take up speed. Morphological characterizations were made by using polarized optical microscope (POM) and small angle X-ray scattering (SAXS). Birefringence data of fibers calculated by using POM images and DDR of samples. For all fibers, increasing of DDR lead to increase birefringence. The other result was that increasing of POSS content caused the decrease of birefringence values with the comparison of neat PP. SAXS pattern clearly showed that isotropy of fibers increases with increasing of POSS content. On the other side, increasing of take up speed increases anisotropy. Increasing of take up speed also increased the fiber orientation. Furthermore, it was observed that high POSS content fibers have more isotropic structure. In consideration of this observation it is clearly seen that POSS content effects the morphology of fibers significantly.
Statistical mixture design of experiment studies for UV curable coating formulations for acrylonitrile butadiene styrene (ABS) substrates
This thesis was studied in cooperation of Arçelik A.Ş. to fulfill the goal of developing high stratch resistance, environment friendly, water-borne, UV curable, transparent coating formulation for Acrylonitrile butadiene styrene (ABS) surfaces. ABS and Polycarbonate/acyrlonitrile butadiene styrene (PC/ABS) is used for plastic parts of the small home appliances as an example top covers of coffe machines and dishwashers in Arçelik A.Ş. and its stratch resistance is very low (0,1 N) like the most of all plastics as well. Therefore it can be stratched easily and lost their appealing, gloss appearance in a short time. This issue cause to displeasure and complaints of customers decrasing the preferability of the products between the other brands. Two different solution can be offered for this problem. It might be added some additives to increase the stratch resistance of plastics which is a harder way. On the other hand, high stratch resistance coating formulation can be developed as a more practical solution. In Arçelik A.Ş., different kind of functional coatings are used for good appearance (gloss, colour), corrosion-protection, anti-finger and easy to clean surfaces. However, currently all kind of coatings which are used in Arçelik, are cured thermally. These thermally cured coatings are not energy-saving because of their high curing temperature and long curing time. In contrast UV-curable of coatings are energy-saving with their application in ambient curing temperatures in addition, it provide to able to cure temperature-sensitive substrates like plastics. The other superior property over the themal curing system is obtaining higher stratch resistance and gloss coatings using UV curing systems. Considering of these advantages of UV-curable coatings, this thesis study objected to developing coating formulation and applying the formulation to ABS surfaces using in products in Arçelik and UV curing of it. As it is know, it is not meaningful to obtain high stratch resistance coating but it is not adhesive to substrate with a long-time durability. Therefore adhesion to surface is the most significant issue to overcome. To ensure for quality, coatings are tested by different test methods according the Arçelik quality requirements for stratch resistance aiming to increase 0.1 N to 3 N, 100% adhesion to surface and their durability against to different chemical and physical effects.
Effects of anionic surfactants on styrene-acrylic copolymer emulsion for wood coatings
Wood coatings have the biggest share in industrial coatings market. Because of high VOC content of conventional solvent-based systems, the market share of low-VOC systems are increasing year by year. Because of the low cost and ease of application of water- based 1K acrylic emulsion systems, they have the biggest increase within low-VOC systems. Water-based 1K acrylic systems differentiate in terms of their end use application and application method. It is convenient for brush, spray, curtain or roller coater systems. It has a wide range of application like furniture, exterior wood substrates, floors, industrial mdf panels, etc. From chemical point of view, styrene-acrylic copolymers, pure acrylic copolymers or vinyl acrylic copolymers can be used in several wood coating application. Main performance criterias are hardness, early hardness development, sandability of the film, scratching resistance, drying time, blocking resistance, chemical resistance and asthetistical properties. The aim of this study is to examine how a range of different anionic surfactants affect the polymerization of styrene-acrylic emulsion and the end properties of an interior clear wood coating system prepared with these copolymers. The surfactants used in this study include different types of anionic surfactants as sodium lauryl suphate, sodium lauryl ether sulphate (2EO and 4EO), sodiım dodecylbenzene sulphonate, alkyl polyethylene glycol ether sulphate, polyoxyhethylene tridceyl phospate ester and disodium exthoxylated alcohol [C10-C12] half ester of sulfosuccinic acid.
ATRP ile bor içeren polimetilmetakrilat sentezi
In this study first of all two different initiators were created and then these two initiators were used in ATRP reaction effectively. Hydroxyl groups were changed with active bromide group with the help of. 2-bromopropionyl bromide that are take part in Carboranemonool and carboranediol structures. FT-IR and NMR methods were used for characterization of initiators.Carborane initiators were used for polymerization of methylmethacrylate.Mainly the effect of reaction time was examined onto the polymerization.Conversions of polymers were determined gravimetrically.Gel permeation chromotography (GPC) was used to determine molecular weight of all polymers,Differential scanning calorimetry (DSC),were used to determine Tg values of all polymers Thermogravimetric analyser (TGA) were used to determine 50% percent degradation time and char yield amount of polymers at 500 oC and 800 oC.These methods were used for characterization of all polymers
Synthesis of styrene-acrylic copolymers and their use in paint
In this study, different types of silanes, which have different structures, are added directly to the styrene-acrylic copolymers. These copolymers are formulated in high PVC paint formulation. These paints are tested in according to their scrub resistance, hardness and flexibility properties.
Investigation of effect of bitumen chemical composition, polymer and warm mix asphalt additives on the properties of bitumen by using response surface method
Bitumen, a binder material used in asphalt applications, is one of the important components that affects the service-life of asphalt. Bitumen chemistry, and amounts of Saturate, Aromatic, Resin, Asphaltene (SARA) fractions within the bitumen, affect the properties of both base and modified bitumen. The desired properties of bitumen change with varying content of bitumen and purpose of application. To improve the properties and the performance while using in the asphalt mixtures usually the polymer addition is utilized. While thermoplastic elastomers are mostly preferred, plastomers such as polypropylene, ethylene vinyl acetate, and natural / synthetic rubber can also be used for the modification of bitumen. The addition of materials like Styrene-Butadien-Styrene (SBS) copolymer can simultaneously develop the durability and flexibility at high temperatures by containing the both soft and hard segments in its structure. In addition, hot mix asphalt additives can be used to prepare bitumen-aggregate mixtures at lower temperatures in order to improve the application conditions. For this purpose, organic or chemical additives included into the bitumen, as well as processes with the foaming techniques can be used for lowering the mixing and layout temperatures. Influence of all these additives on the properties of bitumen changes with the type and amount of additive and bitumen chemistry. An additive applied to improve the some properties of bitumen may adversely affect another feature of the bitumen and consequently asphalt. Especially when the addition of these additives together and variety in the bitumen chemistry are taken into consideration, the desired properties may not be obtained in the final product. Therefore, understanding the simultaneous effect of the variation of bitumen composition, amount of polymer and warm mix additive on the bitumen properties is aimed in this study. Experimental statistical methods were used for this purpose and the effects of independent parameters on the response functions individually and simultaneously were investigated by using Response Surface Method. The composition of bitumen and the amount of polymer and warm mix asphalt additives were defined as independent variables in this study. Dynamic shear rheometer (DSR), Bending beam rheometer (BBR), Elastic recovery and Viscosity were determined as response functions of this system. The effects of these independent variables on the response functions were investigated by the full factorial analysis initially and then the response surface method. In the experimental study, SARA analysis was performed on the bitumens which are in the same penetration grade and obtained from Izmit, İzmir and Batman refineries. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR), Simulated Distillation Gas Chromatography (GC-SimDis), Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were performed for detailed characterization of the bitumens. Styrene-Butadiene-Styrene (SBS) tri-block copolymer and a commercial paraffin wax were used as warm mix asphalt additives for the modifications of the bitumens. FTIR, DSC and TGA analysis were carried out to determine whether these additives can be used in bitumen blends. When the results of characterization tests and chemistry of bitumen were considered together, it can be seen that the same penetration grade bitumens may have different chemical properties and when the performance grade was determined according to TS EN 14023 standardization it may be also found different. This result shows that it cannot be achieved same performance grade by applying the same modifications to the same penetration grade bitumens which have different chemical compositions. Moreover the difference of SARA fractions in the three bitumens could not be seen in the FTIR analysis. The reason for the lower initial boiling point observed in GC-Simdis and the low temperatures at which loss of mass starts for Batman bitumen in TGA analysis are due to the light fractions of the Batman bitumen rather than the amount of saturated content. On the other hand, the high amount of aromatic and saturated structures in the bitumen decreased the glass transition temperature of Izmit bitumen. For the characterization analysis of the additives, it has been proved that the properties of the additives are the same as those of the commercially available common ones having without extra features. The Gaestel index (GI), one of the independent parameters, was used to define the bitumen chemistry in a single variable and examine the effect of bitumen chemistry on the response functions. The GI values of İzmit, İzmir and Batman bitumens were calculated by using the determined SARA fractions as 0.487, 0.622 and 0.988, respectively. In the experimental design matrix, 3 discrete values (0.487, 0.622, 0.988) were defined for the GI as discrete numeric variable, and 2-5%, 1-3% upper and lower limit values for the SBS and Wax, respectively, which were defined as continuous variables. Within these limits, bitumen modifications were made according to the experimental matrix designed by JMP® software and DSR, Viscosity, Elastic recovery and BBR tests which were determined as response functions of system, were carried out. Model equations were constructed with response functions of independent variables by using the data obtained from the measurements and the response surface method. Three-dimensional response surfaces and two-dimensional interaction curves are plotted by using the model data that indicates the effect of each parameter on the properties of bitumen. For the individual analysis, all independent variables were found as significant in different degrees for DSR and BBR response functions. The increasing amount of SBS promotes the value of DSR and creep stiffness exponentially. However this increasing trend affects the creep stiffness negatively since it has the upper limit in the standard. Furthermore the bitumen composition which was defined as GI in the analysis, was an effective term on the all response functions especially for elastic recovery, viscosity and DSR properties which improve rapidly with the increasing value of GI. The higher amount of asphaltene and saturates or lower amount of resins and aromatics enhance the higher value of GI. On the other hand, the amount of wax were determined as insignificant on the viscosity and elastic recovery properties of bitumen despite the fact that the wax is known as an organic additive for viscosity decreasing in the asphalt mixtures. This may be the result of the fact that the viscosity decreasing effect of Wax is very small, comparing with the increasing effect of the SBS and GI. Finally, the optimum values of variables were determined by performing the simultaneous analysis of independent variables with the four response functions together within the desired performance limits. The optimization analysis showed that all variables have effects on the response functions in different degrees. When the result of simultaneous analysis of response functions were compared to the individual analysis, there were terms added or eliminated from the model expression. Especially the GI*GI term which is important for the effect of bitumen composition on the response function was found as insignificant for DSR, Viscosity and Elastic recovery responses in simultaneous analysis. The reason for this was shown as the given limitation for the maximization of DSR and Elastic recovery and the minimization of viscosity. The optimum variable values within the given response limits are GI: 0.988, SBS: 3.2% and Wax: 3%. Tests within the scope of EN 14023 standard and asphalt tests were carried out on modified bitumen prepared in optimum values to investigate the improvement on the performance on both bitumen and asphalt properties. The performance grade of neat Batman bitumen was found to be PG 70-22 while it was determined as PG 82-16 after the modification at optimum conditions. As a result of the modification, while the high temperature performance of bitumen improves as two performance grade, the low temperature performance was affected negatively. The reason maybe that all the modified bitumen samples has the result on BBR as -16 since the addition of SBS increases the creep stiffness and although the amount of SBS is minimum (%2), the performance criterion was not achieved on -22. As a result of the Marshall asphalt design for determining the asphalt properties, aggregate-bitumen blends had 4.8% of the unmodified bitumen, whereas it was necessary to use 6.2% of the modified bitumen. Asphalt samples prepared by using the amounts of bitumen found in design and tested on the wheel tracking test machine. The amount of rutting were found as 13% for unmodified bitumen, while in the modified bitumen this value was improved by 50% to 6.7%. Thus, the DSR, viscosity, elastic recovery and creep stiffness properties of the bitumen have been successfully modelled based on the bitumen content, amount of polymer and warm mix asphalt additives and optimum mixing ratios have been successfully determined by using the "Response Surface Method". The widespread use of experimental design methods will provide a scientific and realistic basis for the preparation of asphalt mixture formulations instead of personal experience as well as the prevention of waste of time.
Grafting of poly(acrylamide) onto crosslinked poly(HEMA-co-MMA) resin for removal of phenol and bisphenol A
Phenol and its substituted derivatives are widely found in the effluents from pesticides, synthetic rubber, plastic, pharmaceuticals, petrochemicals, and other industries. It is also used in the production of caprolactam and bisphenol A. They are intermediates in the manufacture of nylon and epoxy resins, respectively. It is primarily used in the production of phenolic resins, which are needed in the automotive plywood, construction and appliance industries. Other important uses of phenol are as a disinfectant and in medicinal products. Minor uses of phenol contain the manufacture of paint and varnish removers, lacquers, paints, rubber, ink, illuminating gases, tanning dyes, perfumes, soaps and toys Phenol and phenolic compounds are generally considered as one of the important organic pollutants discharged into the environment causing unpleasant taste and odor of drinking water. Even at very low concentrations in the presence of water, is undesirable and toxic to the aquatic beings including fish. Especially, chlorinated phenols are more toxic to aquatic life. Phenols have great risk to the human health and cause negative effects on the brain, digestive system, heart, eye, liver, kidney, lung, peripheral nerve, skin and the unborn child. 0.002 mg L-1 is the permissible limit for phenol concentration in potable water according to the World Health Organization regulation. Removal of phenolic pollutants in aqueous solutions can be divided into three main categories: chemical, physical and biological treatment. Several wastewater treatment methods for removal of phenolic pollutants have been used including membrane filtration, advanced oxidation, biological degradation, photocatalytic degradation, electrochemical oxidation and adsorption. Adsorpsion is very important method to remove organic and inorganic pollutants. Different adsorbents such as zeolites, carbon nanotubes, polymeric sorbents and clay have been investigated for the removal of phenol and phenolic pollutants from wastewater. Three mechanisms of phenolic compounds adsorption is postulated namely, π-π dispersion interaction, electron-donor acceptor complex formation and hydrogen bond formation. This methodology was used to prepare new polymeric sorbents for phenol removal. In this thesis, two types of polymeric sorbents were prepared for removal of phenol and BPA from water. The poly(HEMA-MMA-EGDMA) terpolymer were prepared by using suspension polymerization method starting from polymerization of hydroxyethyl methacrylate (HEMA) (50%), methyl methacrylate (MMA) (40%) and ethylene glycol dimethacrylate (EGDMA) (10%) as crosslinkerin the presence of toluene as porogen and AIBN as an initiator (resin 1). Other polymeric resin was prepared grafting polymerization of poly (acrylamide) onto resin 1 by redox polymerization method. Grafting reaction is carried out through the hydroxyl groups on HEMA units. The resulting polymer resin2 , which had a total nitrogen content of about 7.0 mmol/g, was effective in extracting phenol from aqueous solutions.The phenol and BPA sorption capacities were found depending on concentration and pH. Also, phenol and BPA sorption kinetics of the resins were investigated. Kinetic models were applied for Resin 1 and Resin 2.
Synthesis of bio based polyurethane surface coating materials and characterization
During the last few years, there is a continuous search of advanced polymeric materials for coating applications. Polyurethane resins are a class of thermosetting polymer materials largely used in high performance surface coatings and paints. Fast depletion of petroleum stock and increase in their cost puts limit to their use in future for production of petroleum-based resins. Renewable resources used in the preparation of polymers are falling in the class of biomaterials which are rich in hydrocarbons and most of the times obtained from parts of profusely available agriculture feed stock. The current oil based polymers are prepared by consuming petroleum based anhydrides and dicarboxylic acids. Use of non-edible vegetable oils and their fatty acids are currently the raw materials focused in synthesizing polymeric materials as renewable sources due to increasing economic and environmental concerns of petroleums. Polyurethanes have found many applications starting from coating, paint, foam, thermosetting, thermoplastic elastomer to fiber. However, their relatively low abrasion and wear resistance and environmental degradation, limit their application in surface coating. In the past decade, nanostructure organic-inorganic composites based on organic polymer and inorganic materials have attracted great interest of researchers.These composites exhibit the enhanced performance properties compared to conventional composites because of the maximized interfacial contact between the organic and inorganic phases. So, proper design of polyurethane with appropriate structure and composition of the components may result unique and useful properties for its different end applications. In the present work we have attempted to utilize the castor oil for the synthesis of biopolyurethane coating material. The double bonds in triglycerides are not active enough to take part in free radical polymerization reaction generally. Maleation is a method to increase crosslink density of the final polymer thanks to reactive maleate double bonds. To convert maleated oils into polyols, it was first epoxidized. Hydroxylation of castor oil was carried out with hydrogen peroxide. It was further reacted with different isocyanates in different ratios to develop a series of biopolyurethanes. The synthesized polyurethanes were characterized for the evaluation of their chemical and thermal properties and the effect of isocyanates loading into polyurethane on these properties are also being presented. The thermal properties of biopolyurethane coating materials were studied using thermo gravimetric analysis (TGA). The effect of NCO/OH molar ratio on thermal and mechanical properties of coatings was studied for the prepared biopolyurethane coatings.