Superior Strength-Toughness Balance of Sustainable Polylactide/Poly(butylene adipate- <i>co</i> -terephthalate) Blends Modified by Biomass-Based Pentamethylene Diisocyanate: Synergistic Effect of Interfacial Compatibilization and Chain Extension

Sustainable polylactide/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends demonstrate significant potential across multiple applications. However, the immiscibility of PLA and PBAT usually results in a poor strength-toughness balance, which is the major obstacle to promoting practical use. For addressing this issue, biomass-based pentamethylene diisocyanate (PDI), capable of serving as both compatibilizer and chain extender, was used to modify the PLA/PBAT blends. It was revealed that the carbamate reaction occurring between diisocyanate of PDI with terminated hydroxyl groups of PLA/PBAT led to the formation of extended PLA, chain-extended PBAT, and PLA–PDI-PBAT copolymers, which not only enhanced the chain entanglement of individual phases but also improved the interfacial compatibilization of two phases. Compared to the pristine blend, the PDI-treated blends showed a more blurred phase boundary with a decreased PBAT domain size. The blend with 2.0 phr PDI showed the best mechanical performance with the fracture strain up to 482.4% and a high strength of 42.8 MPa. This work provides a facile approach for developing PLA/PBAT blends with a superior strength-toughness balance, exhibiting considerable promise for industrial applications.