Preparation of flexible poly(l-lactide)-b-poly(ethylene glycol)-b-poly(l-lactide)/talcum/thermoplastic starch ternary composites for use as heat-resistant and single-use bioplastics

Poly(l-lactide)-b-poly(ethylene glycol)-b-poly(l-lactide) block copolymer (PLLA-PEG-PLLA) is a highly flexible bioplastic, yet its use in practical applications is limited due to its poor heat resistance and high production cost. In this study, talcum was used as a nucleating agent to improve the heat resistance, and thermoplastic starch (TPS) was used as a low-cost filler to reduce the cost of production. PLLA-PEG-PLLA/talcum/TPS and PLLA/talcum/TPS ternary composites with 4 wt% talcum and various TPS contents were prepared by melt blending before injection molding and were then evaluated. When PEG middle-blocks were present, the PLLA-PEG-PLLA-based composites showed a higher crystallinity, more flexibility, and a higher heat resistance than the PLLA-based composites. Although the addition of TPS decreased the heat resistance of all the composites, the PLLA-PEG-PLLA/talcum/TPS composites still had high Vicat softening temperatures (VST, 113-131 °C) and demonstrated a good dimensional stability to heat by maintaining their original shapes upon heat exposure. The biodegradation test in soil suggested that the synergistic effect of the PEG middle-blocks and TPS significantly increased the biodegradability of the PLLA-PEG-PLLA/talcum/TPS composites. This improved heat resistance, lower cost, and accelerated biodegradation make PLLA-PEG-PLLA/talcum/TPS composites a promising material to be used as heat-resistant and single-use bioplastic products.