The Influence of Wood Flour and Recycled High-Density Polyethylene on the Mechanical Performance of Wood–Plastic Composites (WPCs)

Plastic waste poses a growing environmental challenge due to the extensive use of plastics in packaging applications. Recycling plastics offers environmental and economic advantages. Wood flour-derived from cypress wood, often generated as a by-product and discarded in landfills, contributes to environmental In this study, wood–plastic composites were fabricated from recycled high-density polyethylene, wood flour, and high-density polyethylene with maleic anhydride-grafted polyethylene as a coupling agent. Five composite formulations were produced by varying the recycled high-density polyethylene and wood flour volume ratios and processed through injection molding. The mechanical properties, including flexural, tensile, and impact strengths, along with water absorption behavior and microstructural characteristics, were evaluated in accordance with relevant standards using a universal testing machine, Charpy impact test, and scanning electron microscopy. The results revealed that increasing the recycled high-density polyethylene content from 20% to 35% significantly improved the composite performance, reducing water absorption by 9.86% and enhancing flexural, tensile, and impact strengths by 43.33%, 36%, and 35.03%, respectively. Morphological analysis confirmed improved fiber–matrix interfacial adhesion with higher recycled plastic content. These findings demonstrate the potential of recycled high-density polyethylene wood composites as sustainable materials for structural applications, combining environmental benefits with enhanced mechanical performance.