Triple shape memory effect of ethylene-vinyl acetate copolymer/poly(propylene carbonate) blends with broad composite ratios and phase morphologies

Abstract

In this work, a triple-shape memory polymer (SMP) was prepared by chemically crosslinking melting blending from ethylene-vinyl acetate copolymer (EVA) and poly(propylene carbonate) (PPC). The EVA/PPC blends combine the glass transition of PPC (~25.6 °C) and melting transition of EVA (~72.2 °C) to function as the shape memory mechanisms. The triple-shape memory effect (triple-SME) and its dependence on composite ratios and micro-phase morphologies were systematically investigated. The results show that EVA/PPC blends with different composite ratios and morphologies all exhibit excellent triple-SMEs, with shape fixing ratio over 90% and shape recovery ratio close to 90%. The key to realize such triple SME is the certain matching of the modulus of the two components. Specifically, the modulus of glassy PPC is much higher than the modulus of semi-crystalline EVA, whereas the modulus of viscoelastic PPC is lower than the modulus of semi-crystalline and elastic EVA. This work provides a comparatively simple and efficient method to design and prepare high-performance triple-SMP.