Toughening polylactic acid by melt blending with polybutylene adipate-co-terephthalate and natural rubber, and the performance of the resulting ternary blends

摘要

Polylactic acid (PLA) is one of the most commercially potential bio-based and biodegradable materials recently used to partially replace non-biodegradable petroleum-based plastics; however, PLA's innate brittleness limits its practical applications. The present work aims to reduce the brittleness and improve the toughness of PLA by blending it with polybutylene adipate-co-terephthalate (PBAT) and natural rubber (NR). PLA/PBAT/NR ternary blends were prepared by a melt blending process, using both an internal mixer and a twin-screw extruder, and were converted into test specimens using an injection molding machine. The weight ratio of PBAT:NR was kept constant at 1:1, while the amounts of PBAT/NR blend were varied at 14, 26, and 38 wt. SEM confirmed the incompatibility among PLA, PBAT, and NR, as island-like NR phases and oval PBAT phases were dispersed in the PLA matrix. Compared with neat PLA, the PLA/PBAT/NR ternary blends exhibited increased elongation at break from 6.2 to 21.0 (up to 240), improved impact strength from 36.6 to 85.0 J/m (up to 130), decreased density from 1.254 to 1.159 g/cm(3) (approximately 7.6), enhanced thermal stability and water resistance, and reduced shear-dependent behavior. The obtained PLA/PBAT/NR blends have potential for the production of injection-molded articles such as biomedical devices, toys, agricultural supplies, office supplies.