Unveiling Favorable Mechanical Properties of Lignocellulosic Wood–Reinforced Thermoplastic Composites as Future Green and Sustainable Materials

The widespread use of synthetic thermoplastics has raised significant environmental concerns, highlighting the need for sustainable alternatives. Their crystallinity primarily influences the biodegradability of synthetic thermoplastic polymers. Reinforcing amorphous wood fibers into thermoplastic polymers can enhance biodegradability and energy absorption. Nonetheless, challenges arise from high water absorption, porosity, and reduced mechanical properties because of the incompatibility between hydrophilic wood reinforcement and hydrophobic thermoplastic matrices. To overcome these challenges, wood fibers can be modified through chemical and physical treatments before compounding with thermoplastics. Optimal treatment conditions, including 6% NaOH for two h and 2% 3-aminopropyltriethoxysilane for three h, resulted in a 35.2% increase in tensile strength while reducing porosity and water absorption compared to untreated fibers. In addition, silane coupling agents like tetramethylcyclotetrasiloxane and perfluorodecyltriethoxysilane enhanced the hydrophobicity of the wood. Treatment with 0.5% potassium permanganate for 3 min yielded higher tensile stress and elongation than untreated composites, attributed to the uniform dispersion of the wood fibers within the matrix. The incorporation of maleated polypropylene or polyethene as binding agents enhanced interfacial adhesion. Among the composites studied, polylactic acid reinforced with 10–20% thermally treated beech wood exhibited the highest tensile strength from 45 to 57 MPa, while polypropylene reinforced with 30% wood achieved the highest tensile modulus at 3.25 GPa. The relationship between wood species, thermoplastic type, and treatment methods is critical for optimizing the mechanical properties of these composites, with potential applications in household utilities, automotive components, and building materials.