Influence of particle size and blending ratio on the physical and mechanical properties of falcata sawdust-recycled LDPE wood-plastic composites

The increasing accumulation of wood and plastic waste necessitates the development of sustainable, value-added materials such as wood-plastic composites (WPCs). This study investigated the feasibility of utilizing Falcataria moluccana (falcata) sawdust as a reinforcing filler in a recycled low-density polyethylene (LDPE) matrix. WPCs were fabricated via twin-screw extrusion using three sawdust particle sizes—P20R40 (0,840 - 0,400 mm), P40R60 (0,400 - 0,250 mm), and P60 (<0,250 mm)—at blending ratios of 30:70 and 40:60 (sawdust:LDPE, by weight). Physical properties, including relative density, moisture content, water absorption, and thickness swelling, were evaluated alongside mechanical performance according to ASTM standards. The results demonstrated that the incorporation of sawdust produced WPCs with physical stability and hygroscopic properties comparable to or superior to those of the pure recycled LDPE control. Mechanical analysis revealed a significant reinforcement effect; the inclusion of sawdust enhanced both the tensile and flexural strength and modulus of the composites. Specifically, finer sawdust particles (<0,250 mm) and a 30:70 sawdust-to-LDPE ratio yielded the optimal overall mechanical performance. However, impact strength tests indicated that the wood filler increased material brittleness, as the neat LDPE significantly outperformed all WPC treatments in energy absorption. Overall, this study concludes that falcata sawdust is a viable natural fiber for reinforcing recycled LDPE, offering a sustainable pathway for upcycling waste into rigid composite materials, provided that applications account for the inherent reduction in impact resistance.