Enhancing Biodegradability of Poly(L-Lactic Acid) via Incorporation of Thermoplastic Chitosan

Poly(L-lactic acid) (PLLA) is a biodegradable polyester that has garnered widespread attention for its potential applications as a replacement for conventional petroleum-based plastics. However, PLLA's prolonged biodegradation is a significant limitation in its applications, particularly in single-use packaging, as it can lead to environmental accumulation and hinder the sustainability goals of reducing plastic waste. This paper examines the effect of incorporating thermoplastic chitosan (TPC) on the mechanical and biodegradation properties of PLLA. TPC was prepared using lactic acid as a plasticizer. PLLA/TPC composites were produced by thermo-mechanical processes. TPC contents of 1%, 2.5%, 5%, and 10% were investigated. The PLLA/TPC films exhibited distinct phase separation, as verified by scanning electron microscopy analysis. The incorporation of 2.5% TPC led to a 20.8% enhancement in elongation at break and a 7.4% improvement in tensile toughness relative to pure PLLA film. Nonetheless, both values diminished when the TPC content surpassed 2.5 wt%. The surface wettability of the PLLA/TPC films, assessed via water contact angle measurements and weight loss from soil burial tests, enhanced with greater TPC content. The PLLA/TPC films showed significantly greater weight loss after being buried in soil for 12 months compared to pure PLLA film. The increases in weight loss were 4, 11, 14, and 72 times greater for the TPC contents of 1%, 2.5%, 5%, and 10%, respectively. Incorporating TPC in this study improved the flexibility and biodegradability of PLLA, leading to PLLA-based composites with enhanced potential for environmentally sustainable single-use packaging.