Biodegradable blends of poly(butylene succinate-co-terephthalate) and stereocomplex polylactide with enhanced rheological, mechanical properties, heat resistance and hydrolytic degradation

Poly(butylene succinate-co-terephthalate) is a biodegradable polymer with good biodegradability, high flexibility and toughness. However, its relatively low modulus, low yield strength and low heat distortion temperature limit its applicability. Herein, equimolar poly(L-lactic acid) (PLLA) and poly(D-lactide acid) (PDLA) were blended with PBST to form stereocomplex poly(lactic acid) (sc-PLA) in situ during melt blending process and prepare a novel and environmentally friendly PBST/sc-PLA blend. Differential scanning calorimetry and wide-angle X-ray diffraction confirmed that sc-PLA had formed in PBST matrix. The morphology of the cryo-fractured surfaces of PBST/sc-PLA blends showed that the sc-PLA was uniformly dispersed in PBST matrix. When the content of sc-PLA is up to 20 wt%, the PBST/sc-PLA blends showed a solid-like flow behavior at the low-frequency region. Moreover, sc-PLA could reinforce the PBST matrix. Young's modulus, yield strength and storage modulus of the PBST/sc-PLA blend increased with increasing sc-PLA content. In addition, the Vicat softening temperature and heat deflection temperatures of PBST/sc-PLA blends increased with the incorporation of sc-PLA, which enhanced the heat resistance. Compared with neat PBST, the hydrolytic degradation of the PBST/sc-PLA blends was improved. This work provides an effective way to obtain high performance PBST materials which could expand the application of PBST.