Roles of physical filling and chemical crosslinking on the physico‐mechanical properties of polylactic acid

Abstract Polylactic acid (PLA) modified materials were prepared with physical filling and chemical crosslinking methods by melt extrusion respectively in this work, and the mechanical, rheological, crystalline, and heat resistance properties were investigated. It is found that filling with talc as the nucleating agent enhanced the crystallization capacity of PLA evidently. When 2 wt% talc was added into the PLA matrix, the crystallinity increased to 30.69% from 6.53% for neat PLA, enhancing by more than 3.6 times. Meanwhile heat resistance of talc filled PLA was improved significantly after annealing, increasing the heat deflection temperature from below 55 °C for neat PLA to about 130 °C for 2 wt% talc filled PLA. Molecular chains entanglement and spatial structures formation due to crosslinking reactions played key roles in tailoring the tensile, rheological properties and melt strengths of PLA materials. The elongation at break of the modified PLA materials increased by 149% and 126% separately after the crosslinking reactions with and without talc. The melt flow index decreased to 1.70 g/10 min after crosslinking from 11.79 g/10 min of neat PLA, indicating that crosslinking reactions exert significant effects on improving melt strength of PLA.