Investigation of the effects of commercial polymer additives on zeolite filled recycled polypropylene composites

Plastic materials are used in numerous fields in daily life. In time, plastics has found new application fields by new studies, discovers and developments. They are used extensively at packaging, automotive, household, healthcare, defense industries, and more due to their low cost and high performance. However, this huge consumption brings waste problems of life ended and scrap plastics. In these circumstances, plastic recycling is inevitable due to difficult biodegradation of most plastics. Especially, recycling of thermoplastics by remelting has not only environmental benefits but also economic benefits. Thermoplastics can be found place in production as raw material by recycling. There are four types of recycling; primary, secondary, tertiary and quaternary. In primary recycling, scraps which are came from production processes are recycled by mechanical recycling methods. These recycled materials are mixed in specific portions with virgin raw materials at the same production. At secondary recycling, produced scraps and life ended plastic products are recycled with mechanical recycling methods and use as raw material at low profile applications due to their lower properties than those of original raw material. Tertiary recycling type can be explained as plastic wastes are processed into basic chemicals like their monomer, to repolymerized. Quaternary recycling means plastic wastes are used as fossil fuel like uses at cement factories. Even though primary and secondary recycle types are extensively performed, tertiary and quaternary recycle types are uncommon due to their costs and environmental effects. By PP recycling and using recycled materials as secondary sources, the foreign source dependency and foreign trade deficit are decreased, and new employment opportunities are provided with the development of recycling industry. Also, plastic recycling provides saving at cost of waste management by reducing landfill. In addition, a developed recycling industry can import plastic waste for produce low cost plastic raw material via recycling. Polypropylene (PP) is a thermoplastic that widely used and consumed. After 1960s, PP was commercialized rapidly and nowadays it still a has rising trend. PP is widely used at packaging applications, electrical appliances and households. Distribution of world polypropylene usage in 2016 by industries is; 49% packaging industry, 31% electronic and household industries, 8% automotive industry and the rest of it is other industries such as agriculture and textile. It should be known that yogurt containers, cups, kitchen boxes, chairs and tables, crazes, bottle caps, some bottles and more are made of PP. Due to this intense consumption, recycling of PP has become more important. Post-consumer and industrial PP wastes and scraps are recycled by mechanical recycling in primary and secondary recycling types. PP recycling and its economic benefits are much more important for countries that have high volume PP import. Clinoptilolite which means "boiling stones" is a natural zeolite, it is cheap and abound in nature. Clinoptilolite is a hydrated aluminum silicate in crystalline form as other natural zeolites. Clinoptilolite is used by the reason of its properties like adsorption, ion exchange and molecular sieve. Clinoptilolite is used different fields and application such as soil additive, fertilizer additive, animal feed additive, paper filler, odor and liquid absorber, waste treatment and filtration. Clinoptilolite is a mineral that has potential to find new usage areas due to its low cost, abundance and different features. Better mechanical properties for plastic raw materials can be achieved by using fillers and cost of plastic material are reduced. In this study, clinoptilolite was used as filler in recycled polypropylene (rPP) and the effects of the commercial polymeric additives that ethylene propylene diene monomer (EPDM), propylene based elastomer (Vistamaxx), and maleic anhydrite modified polypropylene (MAH-gPP/ Bondyram) on the properties of rPP was investigated. rPP which were used in this study were produced from scraps of nonwoven baby diaper PP fabrics. rPP material and clinoptilolite with 10%, 20% and 30% rate were mixed. Then 3 different polymer additives which are EPDM, Vistamaxx and MAH-gPP with 5 phr and 10 phr added into Zeolite containing rPP samples in order to investigate the properties of the effects of additives to the rPP-Zeolite mixtures. All mixtures are granulated with twin screw extruder and these granules were used in injection machine to produce tensile, impact, hardness and density test samples according to test standards. Melt flow index, density, impact, tensile, hardness tests were performed to determine structural and mechanical properties of mixtures. Density tests were showed that densities of samples were increased, and this rise were proportional to clinoptilolite filler rate. Density of neat rPP which was 0.92 g/cm3 was raised to 1.04 g/cm3 with 30% clinoptilolite filling. According to the MFI test which were conducted with 2.16 kg weight at 230°C, as filler rate of clinoptilolite was increased, MFI values were decreased, in a word, clinoptilolite filler amount and MFI value were inversely proportional. Samples that contain MAH-g-PP (Bondyram), had higher MFI values than the groups that contain same rate of clinoptilolite fill. Besides, EPDM added samples had lower MFI values than that of the samples that contain same rate of filler. A considerable effect of Vistamaxx on MFI value was not observed. According to the Izod impact test results, impact resistance has been reduced with clinoptilolite filling. As filler rate has been increased, impact strength has been decreased. Elastomeric additives have been showed positive effect on impact strength and impact strengths have been increased. Tensile test results showed that, tensile strength, and elongation have been decreased at 10%, 20%, 30% clinoptilolite filled samples. Modulus has been decreased at 10% and 20% clinoptilolite filled samples but 30% clinoptilolite filled sample showed higher modulus than neat rPP. Elastomeric additives did not show considerable enhancement on tensile strength, but maleic anhydride modified polypropylene added samples have been showed better tensile strength results due to better interaction between polymer matrix and clinoptilolite filler. Accordingly, samples that contain MAH-g-PP have been showed higher modulus than the samples that contain same rate of filler. The elongation results showed that elastomeric additives have been enhanced the elongation. Eventually, tensile tests results showed that enhancement of interface interaction between polymer matrix and filler by adding elastomeric additives to rPP-Zeolite mixtures.