Preparation of Wood Fiber–Polyurethane Plastic Composite with Water Resistance and High Strength

The current widespread use of plastics is a significant source of environmental pollution and increases the carbon load in the atmosphere, which has precipitated an urgent drive to replace plastics with biomass-based materials. In this paper, we prepared a lignocellulose-based, high-strength, water-resistant composite based on eucalyptus waste sawdust combined with a polyurethane prepolymer. The preparation process included pretreating sawdust with deep eutectic solvents (DESs) to remove some of the lignin and hemicellulose. A prepolymer preparation involving isocyanate groups using the prepolymerization of polyethylene glycol (PEG) with hexamethylene diisocyanate (HDI) grafted the prepolymers to the hydroxyl of the pretreated wood fibers, which were subsequently blended with acetylated pretreated sawdust to create the composite. The composite contained 67% wood fibers, possessed good tensile strength, and exhibited Young's moduli of 18 MPa and 484 MPa. It was water-resistant with a contact angle of 92° and had a low water absorption of 32%, and it maintained a wet tensile strength of 5.71 MPa. The composite offers several advantages, including UV protection and thermal stability. This high-performance wood waste composite provides an alternative green production option for producing plastic materials.