Combined use of additives for improving heat resistance and processability of stereocomplex crystallization polylactic acid

Abstract

The limited heat resistance and high brittleness of polylactic acid (PLA) materials pose significant challenges to enabling their broad application. Compared to traditional PLA, stereocomplex polylactide (sc-PLA) offers superior thermal stability and a higher melting point, attributed to the dense packing and strong physical interactions between polymer chains. Specifically, while PLA has a melting temperature of approximately 160–180 °C, sc-PLA can reach a melting temperature of 230 °C. The enhanced thermal stability and improved mechanical properties make sc-PLA a valuable alternative for applications requiring durability. Here, we report a method to enhance the crystallinity and toughness of sc-PLA by mixing poly(l-lactic acid) (PLLA) and poly(d-lactic acid) (PDLA) in addition to using a nucleating agent and toughening agent. Specifically, a PLA and polyethylene glycol block copolymer and PLA microspheres are prepared, with ethylene-methyl acrylate-glycidyl methacrylate used as a toughener. The optimal composition is found to be PLLA/PDLA blends with a 70/30 mass ratio, 1% microsphere nucleating agent and 10% toughener addition. The Vicat softening temperature of this blend is 72.2 °C, approximately 10% higher than the control sample, with toughness increased by about 2.3 times. This blend also presents an enhanced processability by the combined effect of additives. This work provides a promising strategy for producing sc-PLA with enhanced heat resistance and processability, improving the performance for various applications. © 2025 Society of Chemical Industry.