Characterization of Composites from Post-Consumer Polypropylene and Oilseed Pomace Fillers

Abstract

This study investigates the properties of composites produced using post-consumer polypropylene (PP) reinforced with lignocellulosic fillers from Nigella sativa (black cumin) and rapeseed pomace. Using agri-food by-products like pomace supports waste management efforts and reduces the demand for wood in wood–plastic composites. The composite production method combined extrusion and hot flat pressing. Mechanical tests showed a decrease in the tested parameters. Compared to the control variant, the MOE decreased by 26.4% (PP_R variant) and 46.9% (PP_N variant), and the MOR value decreased by 78.7% (PP_N) and 55.1% (PP_R). No significant differences in surface roughness parameters were observed. The composite with nigella particles demonstrated increased wettability. TGA tests showed reduced thermal stability compared to PP and differences between composite variants. The composites exhibited susceptibility to fungal overgrowth, which suggests potential biodegradability. The composites demonstrated complete overgrowth by inoculated fungi, reaching 100% coverage, while samples from PP known to be resistant to biological factors remained unaffected. Although the mechanical properties of the composites were degraded, the use of lignocellulosic fillers offers undeniable advantages, such as waste management of lignocellulosic and polypropylene byproducts, reduced wood demand, and the potential biodegradability of the obtained composites. However, there is a need for further optimization of manufacturing processes and material composition to enhance the material performance.