Tekstiller için aerogel fiber ve kompozitlerinin geliştirilmesi

Aerogels are a class of nanostructured materials with some extraordinary properties like low densities, high porosities, high surface areas and low thermal conductivities. These properties of aerogels make them very attractive as fabrics for thermal insulation, liquid absorption, sound absorption and medical textiles. In this work, pure aerogel fibers and aerogel based nonwoven fibrous composites were prepared. A composite of alginate aerogel with polyester (PET) nonwoven was synthesized by a sol-gel method. A needle punched PET nonwoven was soaked with an alginate solution and then immersed in an aqueous CaCl2 solution which resulted in the formation of a gel inside the PET nonwoven. The gel was dried with supercritical CO2 after solvent exchange with ethanol leading to alginate aerogel-PET nonwoven composite. The aerogels were porous and were in the form of blocks in between the PET fibers as evident from SEM images. The thermal properties of the composite were measured using a heat flow meter. The thermal diffusivity of the composite was significantly lower than the thermal diffusivity of the pure PET nonwoven. The composite also had a higher thermal resistance and a higher tensile strength than the pure PET nonwoven. Experiments using a thermal imaging camera indicated that the heat flux in the composite is much lower than in pure PET nonwoven due to the presence of alginate aerogel. The results show that the new composite material is promising for use in thermal clothing applications. A composite of cellulose aerogel with needle punched cotton nonwoven was also synthesized by a sol-gel method. The cotton nonwoven was immersed inside the solution of cellulose and heated at 50 ºC for 2 hours which led to the formation of layers of gel inside the cotton nonwoven. Then gel was dried with supercritical CO2 after solvent exchange with acetone to obtain cellulose aerogel cotton nonwoven composite. This composite had a highly porous structure and an average pore diameter of 25 nm. The wound exudate (fluid) absorbency test was performed to determine the performance of this composite for wound dressings. The cellulose aerogel cotton nonwoven composite showed high wound exudate absorbency. Furthermore, silver was loaded inside the aerogel composite in order to achieve antimicrobial properties. The composite was soaked in 0.02 M solution of silver nitrate after solvent exchange with acetone and dried supercritically. The composite exhibited excellent antibacterial resistance against Escherichia coli bacteria. The pure aerogel fibers were produced from sodium alginate. Firstly, alginate gel fibers were synthesized by extrusion of an alginate solution (three different concentrations in water) into a CaCl2 aqueous solution using a syringe pump. Removal of water from the gel fibers by solvent exchange with ethanol followed by supercritical extraction of ethanol at 308 K and 10 MPa resulted in alginate aerogel fibers. Three different kinds of alginate aerogel fibers were prepared by changing the concentration of the alginate solution. The aerogel fibers were characterized by mercury porosimetery, scanning electron microscopy, Raman spectroscopy and tensile strength tester. All three fibers were highly porous with surface areas and densities in the range of 220 m2/g to 231 m2/g and 0.2 g/ cm3 to 0.3 g/ cm3 respectively. The maximum elongation of the fibers ranged from 12 % to 15 % while their elastic modulus ranged from 0.26 MPa to 0.45 MPa.