Evaluation of GMA-Modified PLA/Bamboo Composites: Mechanical Strength and Biodegradability

To develop eco-friendly wood-plastic composites (WPCs) with enhanced performance, this study focused on improving the interfacial compatibility between polar plant fibers and the weakly polar polylactic acid (PLA) matrix by grafting glycidyl methacrylate (GMA) onto PLA via solid-phase modification. Using benzoyl peroxide as an initiator in a high-speed mixer, 10 PLA-<i>g</i>-glycidyl methacrylate (PLA-<i>g</i>-GMA) copolymers with varying grafting ratios were synthesized. The chemical structures of these copolymers were characterized using FTIR and ¹H NMR spectroscopy. The results indicated that the grafting degree of PLA initially increased and then decreased with increasing GMA content, peaking at 15% GMA with a grafting rate of 9.62%. Bamboo plastic composites (BPCs) were prepared by hot-pressing PLA-<i>g</i>-GMA with bamboo flour (BF). Physical and mechanical testing showed that both water resistance and mechanical properties of the composites initially improved and then declined with increasing GMA content. Notably, the composite based on 13% GMA-modified PLA exhibited the best water resistance, with a 24 h water absorption of only 1.05%. Composites prepared with 15% GMA-modified PLA showed the best overall performance, showing increases in static flexural strength, elastic modulus, and impact strength by 168.86%, 94.06%, and 45.67%, respectively, compared to the unmodified composite. Additionally, the 15% GMA modification slowed soil-burial degradation. These findings indicate that moderate grafting of PLA significantly enhances interfacial adhesion and performance in biobased composites, providing a theoretical foundation and data support for the design of high-performance, environmentally friendly WPCs.