Toughening of poly(lactic acid) by ethylene-co-vinyl acetate copolymer with different vinyl acetate contents

The well-known bio-based and biocompostable poly(lactic acid), PLA, suffers from brittleness and a low heat distortion temperature. In this paper, we address a possible route to make PLA tough(er) by blending with ethylene-co-vinyl acetate (EVA) with different vinyl acetate contents. The compatibility and phase morphology of the PLA/EVA blends was controlled by the ratio of vinyl acetate and ethylene in the random copolymers. Tough PLA/EVA blends with increased impact toughness, up to a factor of 30, were obtained with a maximum toughness at a vinyl acetate content of approximately 50 wt.%. The local deformation mechanism was well studied by TEM, SAXS and SEM. It revealed that internal rubber cavitation in combination with matrix yielding is the dominant toughening mechanism for the PLA/EVA blends under both impact and tensile testing conditions.