Investigation of the effects of perlite and pumice added to the cast type polyester matrix composite with waste plastic pet powder

The main objective of this study is to composite polyethylene terephthalate (PET) materials, which are found as waste in nature, with liquid cast polyester through certain grinding processes and to form a new composite material by adding perlite and pumice mines, which are pure in nature, in particle sizes in this process. It is aimed to provide an economic advantage in terms of strength and easy availability of these composite materials. In the research, it is also aimed to determine the properties of pumice to increase its strength and to have a more stable and long-lasting structure compared to existing polymer materials and to create a more efficient material in production. The atomic microstructure, surface roughness and strength properties of perlite and pumice doped composite material were analysed using SEM, EDX, XRD, TGA, FT-IR and AFM tests to investigate the microstructures; and hardness, tensile, compression and bending tests to investigate the mechanical behaviour. In this context, composite materials reinforced with certain ratios of perlite and pumice were molded by pouring into silicone molds. The samples created were divided into 9 groups containing different ratios of perlite and pumice. Detailed analyses were performed on a sample selected from each group. The research findings clearly show that the mechanical properties of polyester composites vary significantly depending on the additives used and their combinations. Microhardness values increased approximately 10-fold, reaching 61.55 Hv in the sample containing 50% waste plastic, compared to 6.42 Hv in the matrix sample. In terms of tensile strength, multiple additive combinations showed the highest strength, with sample no. 4 reaching a tensile stress value of 52 N/mm², exceeding the value of the matrix sample (30 N/mm²) by 73%. In terms of compressive strength, sample no. 4 containing 50% waste PET exhibited an extraordinary value of 95 N/mm², increasing the compressive strength of the matrix sample (60 N/mm²) by 60%. In the bending tests, sample no. 2 with raw perlite added reached the highest bending strength with a force of 55 N. These results confirm that waste and natural additives are promising alternatives to optimize structural strength in polyester composites, but careful tuning of additive type, ratio, and combination is critical to obtain the most appropriate material properties for the targeted application. Keywords: Perlite, Pumice, WastePlastic, Composite, Mechanical Property, Microstructure