Design of Supertoughened and Heat-Resistant PLLA/Elastomer Blends by Controlling the Distribution of Stereocomplex Crystallites and the Morphology

Abstract

Supertoughened and heat-resistant poly(l-lactide) (PLLA)/elastomer blends were prepared by controlling the distribution of stereocomplex (sc) crystallites and the morphological change from sea–island structure to cocontinuous-like structure. To control the distribution of sc and the phase morphology, poly(d-lactide) (PDLA) was first blended with ethylene–vinyl acetate–glycidyl methacrylate elastomer (EVMG) to prepare EVMG/PDLA masterbatch comprising both free PDLA and EVMG-g-PDLA copolymers. The free and grafted PDLA would collaborate with PLLA to form sc in the matrix and at the interface, respectively, during subsequent melt-blending of the masterbatch with PLLA. Consequently, the in situ formed sc crystallites not only enhanced the interfacial adhesion but also increased the melt viscosity and crystallization rate of the PLLA matrix. The sc crystallites amount can be tuned via PDLA content to achieve designable properties and cocontinuous-like morphology, leading to highly improved toughness of PLLA; e.g., the notched impact strength of PLLA was increased by 84 times. Moreover, the PLLA/(EVMG/PDLA) blends exhibit both excellent impact toughness (>70 kJ/m2) and heat resistance (E′140°C > 130 MPa) after a simple annealing. This work provides an effective approach toward high performance PLA materials which may expand the application of PLA to more advanced domains.