Improvement of mechanical toughness of poly(lactic acid) by addition of ethylene-vinyl acetate copolymer

摘要

We investigated the structure and properties of binary blends comprising poly(lactic acid) (PLA) as a matrix and ethylene-vinyl acetate copolymer (EVA), by considering the effect of the vinyl acetate (VAc) content in EVA. The interfacial tension with PLA was found to decrease with increasing the VAc content. Therefore, blends comprising EVA with a high VAc content have fine EVA particles, and exhibit marked mechanical toughness and good transparency. Although pure PLA is prone to brittle fractures, the addition of EVA leads to shear yielding, which is prominent when the matrix ligament thickness is shorter than a critical value. The cavitation process in the dispersed EVA particles is also responsible for the mechanical toughness, which is obvious in EVA with a high VAc content.