Thermal, mechanical, rheological and morphological properties of compatible poly(lactic acid)/ethylene vinyl acetate blends

Abstract

This paper examines the effects of poly (ethylene-co-vinyl acetate) (EVA) with 40% vinyl acetate content on thermal, mechanical, rheological, and morphological properties of polylactic acid (PLA) blends. Thermal analysis indicated improvement of crystallinity in the presence of more EVA. With 15% EVA, the impact strength of the binary blend increased significantly (37.80 KJ/m2) at an optimum elongation at break due to the compatibility of the blend and the formation of fibrils. In the presence of % EVA, complete phase separation with the formation of EVA droplets in the PLA continuous phase resulted in a reduction of impact strength and elongation at break. Changes in compatibility and morphology lead to variation in rheological properties. The complex viscosity (η*) decreased with increasing EVA content up to 10% EVA but slightly increased at 15% EVA due to optimum interphase interaction between components in the compatible blend. In the presence of more than 20% EVA, η* reduced again due to the occurrence of phase separation. The variations in the mechanical and rheological properties of PLA/EVA blends are directly related to the state of compatibility and morphology of the blends.