Bio-based polyamide-assisted supertoughening of polylactide through hardening of the EGMA elastomeric domains of much low amount

Abstract

The inherent shortcoming of brittleness for polylactide (PLA) was resolved through a facile melt blending of PLA with both ethylene-acrylic ester-glycidyl methacrylate random terpolymer (EGMA, a soft elastomer) and bio-based polyamide copolymer (PUDA-co-BUDA, a hard elastomer). Surprisingly, the ternary blend containing PLA of 85 wt%, EGMA of 10 wt% and PUDA-co-BUDA of 5 wt% exhibited 26 times higher impact strength (64.2KJ/m2) than that of neat PLA (2.4KJ/m2), and superior stretchability with an elongation at break of 177%. Neither of EGMA and PUDA-co-BUDA could alone provide the same toughening effect at 10 and 5 wt%, respectively. Interfacial tensions between the component pairs and spreading coefficients of the ternary blends predicted the formation of “hard-soft” core-shell complex phase morphology, while scanning electron microscope (SEM) and transmission electron microscope (TEM) confirmed that the hard PUDA-co-BUDA domains were dispersed into the soft EGMA domains. The epoxy groups of EGMA reacted with the functional groups of PLA and PUDA-co-BUDA resulted in sufficient adhesions at PLA/EGMA and EGMA/PUDA-co-BUDA boundaries. The combined effect from both the unique particle microstructures and the interfacial adhesions led to obvious improvement in impact strength, opening a new avenue to expand the application of PLA-based products.