Structure–property correlations of heat‐shrinkable polymer blends based on ethylene vinyl acetate/carboxylated nitrile rubber in the presence of different curatives

Abstract

AbstractElastic memory was introduced into heat‐shrinkable polymer blends in the form of an elastomeric phase and through subsequent crosslinking. Blends of ethylene vinyl acetate and carboxylated nitrile rubber with different curative systems were studied with respect to their shrinkability. With an increase in the cure time (the crosslinking density, or memory point), shrinkage increased for the blends with all the curative systems except dicumyl peroxide (DCP). Increasing the elastomer content increased shrinkability because of the increasing driving retraction force of the oriented elastomer phase. A sample stretched at a high temperature (HT) showed greater shrinkage than a sample stretched at room temperature (RT) because of the greater concentration and degree of orientation of the extended chains. Generally, the crystallinity of the stretched (RT and HT) samples was higher than that of ordinary unstretched and shrunk samples, and this increased the effectiveness of intermolecular interactions in the former. For all systems except DCP, RT‐stretched samples showed higher crystallinity than corresponding HT‐stretched samples. With RT stretching, rapid extension and subsequent recrystallization occurred in samples molten at high local values of the stored elastic energy. An increase in the crosslinking density and orientation of the blends increased the thermal stability because of the formation of strong networks and compact structures. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1414–1420, 2003