Toughening of brittle poly(lactide) with hyperbranched poly(ester-amide) and isocyanate-terminated prepolymer of polybutadiene

The use of polylactide (PLA) in durable applications is currently being hampered by its brittleness and low impact strength. In this study, the effects on mechanical properties of two potential toughening agents for PLA, i.e., hydroxyl-terminated hyperbranched poly (ester amide) and isocyanate-terminated prepolymer of butadiene (ITPB), alone and in combination, are investigated with the aim of making tough PLA blends for use in durable non-food applications such as automotive interior. Synergistic effects in impact strength were observed in PLA ternary blends containing hyperbranched polymer (HBP) and ITPB. Impact strength of the PLA/HBP/ITPB ternary blend was improved by over 86 %, while the elongation at break was increased by over 100 %. Physical and chemical interactions between the hydroxyl-terminated HBP and the ITPB may be responsible for the observed synergistic effect and improvements in impact strength. Tensile, flexural, thermal, and thermo-mechanical properties of the PLA/HBP blends with varying amounts of the ITPB were studied. Scanning electron microscopy images showed evidence of stretched polymer which may indicate that the fracture behavior of PLA changed from brittle to ductile in the PLA/HBP/ITPB ternary blends.