Thermal and Mechanical Properties of Bioplastic Poly(lactic acid) Compounded with Silicone Rubber and Talc

Poly(lactic acid) (PLA) is biodegradable bioplastic with reasonably high tensile strength and modulus. However, its brittleness and low crystallinity led to low thermal stability and limited applications. This research aims to enhance crystallization of PLA by using talc and to improve toughness of PLA by compounding with silicone rubber (SR). Films of PLA/talc and PLA/SR were prepared by using a twin screw extruder with film blowing facility. Mechanical, thermal and physical properties of both PLA/talc and PLA/SR films were investigated. DSC thennograms revealed that the addition of talc raised the degree of crystallinity from 1.4% of the neat PLA to 4.7% for the PLA films with 10 wt% talc. The cold crystallization temperature (T-cc) of PLA also decreased with increasing talc content. The ductility of PLA was significantly improved by blending with SR; the addition of only 3 wt% SR enhanced the elongation at break of the PLA/SR film by about 24 folds to 179.4% compared with 7.4% observed in the neat PLA. Under tension, the PLA/SR film yielded more easily at lower stress than those nucleated with talc. In addition, the increase of talc and SR content led to enhancement of impact strength. Significant surge of impact strength to 732 J/m was found in the PLA film with 3 wt% SR while that of neat PLA film was 328 J/m. Microscopic study revealed talc and SR dispersed and adhered well to the PLA matrix.