Investigation of mechanical and thermal properties of hybrid polyester composites modified with lignocellulosic agricultural wastes and sedimentary rock additives

Although natural fibers (hemp, flax, sugar cane, coconut fiber, corn cob, wheat bran, wood shavings, etc.) have lower mechanical and thermal properties compared to their synthetic counterparts, their use in hybrid polymer composites is increasing [1-7]. These composites, which are environmentally friendly and have better functional properties, are widely used in the aviation, automotive, and construction industries [8-10]. This master's thesis study aims to investigate the mechanical, thermal, and morphological properties of hybrid polyester composites containing sedimentary rock (such as pumice, perlite, and bentonite) and fibrous agricultural waste (such as flax, wheat bran, and sunflower plant stalk). In the first stage of the experimental studies, sedimentary rock will be added to the liquid polyester and agricultural waste fiber mixture prepared in the presence of methyl ethyl ketone peroxide in certain proportions to obtain the composite polymer. In the second stage of the experimental studies, the mechanical strength, thermal stability, and dielectric performances of the prepared composites will be analyzed in detail. Thermal stability and thermal degradation behaviors will be analyzed with a thermogravimetric analysis (TGA) device and the durability performance of the composites in high-temperature environments will be evaluated. In order to determine the dielectric properties, measurements will be made in a wide frequency range and the electrical insulation performances of the composites will be revealed. In the third stage, the surface morphology of the composites will be examined with scanning electron microscope (SEM). The chemical bond structure and interface interactions will be analyzed with Fourier Transform Infrared Spectroscopy (FTIR). In addition, rheological properties of liquid polyester, bulk density of composites, surface hardness and thermal conductivity tests will be performed. With these tests, the distribution of sedimentary rock in the composite matrix and surface quality will be determined and information about the structural integrity of the composites will be obtained. This thesis study aims to contribute to developing more durable, lightweight, and versatile materials by revealing the effect of adding sedimentary rocks, agricultural waste, and polyester mixture to polymer matrices. In addition, environmentally friendly production processes will be based on the principle of low carbon footprint and zero waste. The use of sedimentary rocks offers a significant advantage in the development of sustainable materials and will be beneficial in terms of both easy availability and economic cost. It is expected that the development of low-cost composites using recyclable natural materials and economical composites with recycling potential will play an important role in reducing environmental impact by providing sustainable material solutions in the future.