Triple-shape memory effects of modified semicrystalline ethylene-propylene-diene rubber/poly(epsilon-caprolactone) blends

Abstract

Triple-shape memory polymers (T-SMPs) were prepared by melt blending of a 3-amino-1,2,4-triazole modified semicrystalline maleated ethylene-propylene-diene rubber (A-EPDM), which forms a supramolecular hydrogen-bonded network, with poly(epsilon-caprolactone) (PCL). The effect of PCL content (10-50 wt%) on the thermomechanical and triple-shape memory properties of the A-EPDM/PCL blends was investigated. Scanning electron micrographs showed a phase-separated morphology, in which PCL phase was dispersed in a continuous A-EPDM matrix. Fourier transform infrared spectroscopy and differential scanning calorimetry results revealed a certain degree of compatibility between A-EPDM and PCL in the blends. Dynamic mechanical analysis of the blends showed that the blends form a physically crosslinked network structure and there are sudden drops in the storage modulus at well-separated temperatures in the range of 20-140 degrees C corresponding to the crystalline melting transition of each component in the blends. These structural features of the blend two well-separated crystalline melting transitions within a physically crosslinked network enable this blend system to exhibit triple-shape memory behavior with two different stages of temporary shape fixing and then step-wise shape recovery. These blend-based T-SMPs show melt processability and recyclability. (C) 2015 Elsevier Ltd. All rights reserved.