Super-tough polylactic acid blends via tunable dynamic vulcanization of biobased polyurethanes

Polylactic acid (PLA) is a biobased plastic with biodegradability, biocompatibility, and high-strength properties; however, its inherent brittleness limits its widespread application. Toughness can be improved by physical blending, chemical copolymerization, and reactive blending of PLA with flexible components. As highly engineered block polymers, polyurethanes (PUs) can improve the toughness of PLA through physical blending or in situ polymerization. However, current research on PU-toughened PLA is hindered by poor compatibility, toughening, and dependence on petrochemical resources. Therefore, to address these issues, we developed a novel biobased millable polyurethane (PO3G-MPU) containing unsaturated double bonds and used it to toughen PLA via peroxide-initiated dynamic vulcanization. The results showed that balancing toughness and strength is possible, with the notched impact strength and tensile strength of the prepared PLA/MPU blends reaching 59.01 kJ/m² and 43.97 MPa, respectively. The massive shear yielding and plastic deformation of the PLA matrix induced by the crosslinked PO3G-MPU were responsible for the main toughening mechanism. These results provide a new perspective on research on PU-toughened PLA.