Synergistic Effect of Surface-Modified MgO and Chitin Whiskers on the Hydrolytic Degradation Behavior of Injection Molding Poly(l-lactic acid).

To regulate the degradation behavior of poly(l-lactic acid) (PLLA) for its use as a bone internal fixation material, surface grafted magnesium oxide and chitin whiskers (-MgOs and -CHNs) were added to PLLA in combination or separately via injection molding in this study. The as-prepared binary or ternary composites were degraded in vitro in PBS solution with a pH value of 7.4 at 37.5 °C. The variations in mass, pH value, surface morphology, crystallization performance, melting behavior, and mechanical properties of the samples during the degradation course were systemically considered. The results revealed that the -MgOs accelerated the early degradation of the composite, while the -CHNs played a regulatory role in the later degradation of the composite. Simultaneously adding -MgOs and -CHNs can maintain the mechanical properties of the composite at an early stage but promote the degradation of the composite at a later stage, which suggests that the degradation behavior of the PLLA matrix could be regulated to some extent. This tunable degradation behavior of the -MgOs/-CHNs/PLLA composite is conducive to its application as a bone internal fixation implant.