Crystallinity and mechanical properties of polylactide/ether-amide copolymer blends

The present study focuses on the improvement of impact properties and particularly on the interaction between crystallinity development and mechanical properties of impact modified polylactide (PLA). The PLA was toughened by the addition of a random linear ether-amide copolymer (PEBAX 3533 (TM)). A random copolymer of ethylene, methyl-acrylate, and glycidyl-methacrylate (LOTADER AX8900 (TM)) was also used to reactively compatibilize the ether-amide copolymer with the PLA matrix. Melt rheology of the blends was investigated in small amplitude oscillatory shear and showed that the impact modifier could significantly influence the viscoelastic response of the material. The Izod impact resistance and tensile properties were measured using standard testing protocols. The blend morphology was also examined using scanning electron microscopy on cryofractured and microtomed surfaces, while the crystalline morphology was assessed by optical microscopy. A sub-micron dispersion of the impact modifier was achieved in the presence of the reactive compatibilizer. Significantly improved impact strength was found with 10 wt % impact modifier. High crystallinity samples showed the highest impact strength with values reaching 68 kJ/m(-2), hence a 20-fold improvement with respect to the neat PLA. (C) 2016 Wiley Periodicals, Inc.