Investigation of the use of different agricultural wastes as filler material in polymer composite production

Today, sustainable material production and environmental protection have become an important priority on a global scale. In this context, the recycling of agricultural wastes and their utilization in the production of polymer composites has a great potential both environmentally and economically. This thesis aims to further investigate the potential of utilization of agricultural wastes in the production of polymer composite materials and the environmental and economic impacts of this utilization. The study focuses on how different agricultural wastes - hazelnut shells, walnut shells, almond shells, peanut shells, pistachio shells, hemp seed pulp - can be used in the production of polymer composites. These wastes were mixed with a polypropylene matrix at a ratio of 20% to form granules. Test specimens were produced from the granulated materials by injection molding method. Test specimens were produced by injection molding method from the granulated materials. Mechanical tests (tensile test, bending test, impact test, hardness measurement), thermal tests (DSC, TGA, FT-IR etc.) and microstructure imaging analysis were performed on the test specimens. According to SEM analysis, pure PP exhibited a homogeneous and ductile structure, while biobased additives showed weaker bonding with voids and shrinkage marks at the filler-matrix interface; while better integrated compact structures were observed in pistachio and olive pomace additives. Tensile and three-point bending tests showed that the addition of agricultural waste had an effect on the mechanical properties of the composite. When the impact test results were analyzed, the highest impact strength was observed in pure polypropylene, the reference material with sample code PPAW01. It was determined that agricultural waste additive decreased the impact strength. It was determined that agricultural waste additives increased the Shore D hardness values of the parameters, but not as effective as talc additives. When the density measurement results of the parameters are examined, it is seen that agricultural waste additives lighten the composites. As a result of TGA analyses, it was determined that pure PP showed a single-stage thermal degradation, while composites with agricultural waste additives had a multistage degradation profile due to hemicellulose, cellulose and lignin; these structures increased the residue rates depending ın the additive type and affected the thermal stability. When the thermal properties of the parameters were analyzed, it was determined that agricultural waste additives improved the thermal properties of PP, although not as much as talc.