Effect of the molecular weight of poly(vinyl acetate) on the polymorphism and thermomechanical properties of poly(L-lactic acid)/poly(D-lactic acid) blends

The effects of molecular weight (M-w) and content of poly(vinyl acetate) (PVAc) on the crystallization behaviors, competing crystallization of homocrystallites and stereocomplex crystallites (SCs), crystalline structure, and mechanical properties of poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) blends were investigated. The crystallization of PLLA/PDLA component is accelerated after the addition of low-M-w PVAc and is suppressed with high-M-w PVAc. The ability of SC formation is enhanced via blending with PVAc, irrespective of its M-w, and becomes prominent with low-M-w PVAc. The exclusive SCs are obtained in the blends with 30 mass % low-M-w PVAc. The improvement in thermomechanical property above 170 degrees C is ascribed to the enhancement of SC content. This work presents guidance for achieving the melt processability of SC-PLA, thus proving their potential as a high-performance substitute for conventional plastics.

Automated summary

The study shows that the addition of low-Mw PVAc can accelerate the crystallization of PLLA/PDLA components, while high-Mw PVAc can inhibit crystallization; blending with PVAc enhances the formation of SCs, with the best effect seen with low-Mw PVAc; only SCs are obtained in blends with 30% low-Mw PVAc, improving the thermomechanical properties.