Design of biodegradable PLA/PBAT blends with balanced toughness and strength via interfacial compatibilization and dynamic vulcanization

In this work, we report that super-toughened and high-strength polylactide/poly(butylene adipate-co-terephthalate) (PLA/PBAT) blends can be successfully prepared by interfacial compatibilization and dynamic vulcanization during reactive melt-blending with small amounts (0.5–3 wt %) of epoxy-functional styrene-acrylic oligomers (ESA). The results show that the compatibilization is realized with the grafting of some PLA and PBAT chains onto ESA backbones to in-situ generate PLA-graft-PBAT copolymers at the blend interface. Meanwhile, the ESA-mediated vulcanization gives rise to the highly cross-linked PBAT particles with a unique network-like distribution in the PLA matrix. Both the strengthened interfaces and networked PBAT particles are favorable to the triggering of massive matrix plastic deformation required for effective energy dissipation and thus the toughening effect is substantially enhanced. Impressively, the notched Izod impact toughness and elongation at break of the PLA/PBAT (70/30) blends can reach as high as 62.4 kJ/m2 and 232%, while the tensile strength increases from 44.2 MPa to 51.5 MPa, indicating a balanced toughness and strength. Most notably, it is demonstrated that tuning the molecular structure of ESA (i.e., epoxy group density and backbone length) is essential to improving the interfacial adhesion and phase morphology, enabling high toughening efficiency. Our facile yet robust strategy presents an unprecedented opportunity for the development of high-performance fully biodegradable PLA blends.