Effects of Natural Fiber Waste, Content, and Coupling Agent on the Physical and Mechanical Properties of Wood Species–Plastic Composites as Green Materials

The use of recycled or waste materials is environmentally beneficial. This study focuses on recycled plastic and wood waste which are produced as wood–plastic composites (WPCs). The effect of loading, wood species, and maleic anhydride-grafted polypropylene (MAPP) on the physical and mechanical properties of WPCs is evaluated. Extrusion and compression were employed to produce the composite samples. Three types of wood waste are evaluated, namely rubberwood flour (RWF), coir fiber, and palm fiber at wood loadings of 30, 40, and 50 wt%. The results indicate that loading and wood species significantly affected the hardness, tensile strength, and flexural properties of the WPCs. Moreover, the addition of MAPP had a significant effect on the physical and mechanical properties of WPCs resulting in improved compatibility of wood and polymer matrix and crystallization properties. The highest impact strength (3.88 kJ/m²), tensile strength (25.73 MPa), flexural strength (37.55 MPa), and crystallinity (42.52%) were accomplished at 40 wt% RWF with MAPP. However, the water absorption, hardness, tensile modulus, and flexural modulus of the WPCs increased as the wood loading increased. Moreover, WPCs based on 30 wt% RWF with MAPP had the lowest water absorption (5.59%) after being immersed for 8 weeks. Therefore, this study provides a use for low-cost recycled plastic and wood waste as filler materials for WPCs that can be used in structures and building applications because of their high performance, benefitting both the economy and the environment.