The Effect of Alkali Treatment on the Mechanical Strength, Thermal Stability, and Water Absorption of Bamboo Fiber/PLA Composites

Alkali treatment is a prevalent method to enhance the interfacial compatibility of natural fiber-reinforced polymer composites (NFRPCs). Although the influence of alkali treatment on the properties of NFRPCs has been extensively investigated, previous studies have predominantly examined individual factors in isolation, leaving the combined effects of alkali solution concentration, treatment temperature, and time relatively unexplored. In this study, an orthogonal experiment was conducted to assess the combined impacts of alkali solution (NaOH) concentration, treatment temperature, and time on the mechanical strength, thermal stability, and water absorption of bamboo fiber (BF)/polylactic acid (PLA) composites. The findings indicated that both the NaOH concentration and temperature exhibited a statistically significant effect (0.01 < p < 0.05) on the mechanical strength of BF/PLA composites, while the treatment time had no significant effect. Furthermore, all three factors had an extremely significant impact (p < 0.01) on the thermal stability of BF/PLA composites. The water absorption of BF/PLA composites was found to be significantly influenced by treatment temperature and time (p < 0.01), while no significant effect of NaOH concentration was observed. The optimal combination of alkali treatment parameters (concentration—5 wt%, temperature—25 °C, time—30 min) for BF/PLA composites was determined. Additionally, it was observed that the water absorption of alkali-treated BF/PLA composites was lower than that of untreated composites for shorter dipping times, but higher for prolonged dipping times. This work offers an important reference for the efficient application of alkali treatment to NFRPCs.