Effect of rubber content on mechanical properties and heat shrinkage of ethylene vinyl acetate copolymer blended with epoxidized natural rubber

Abstract

AbstractEthylene vinyl acetate (EVA, 18 mol % vinyl acetate) and epoxidized natural rubber (ENR, 50 mol % epoxidation) were blended in an internal mixer and compared to EVA. Dicumyl peroxide (DCP) was used as a curing agent. The blends consisted of 10–50 wt % of ENR and were compared with crosslinked EVA in terms of heat shrinkage, mechanical properties, and degree of crystallinity. It is found that the blends showed a decrease in mechanical properties with increasing ENR content because DCP was not a good vulcanizing agent of ENR. The addition of ENR did not affect heat shrinkability of EVA. The maximum heat shrinkage obtained was 80% for EVA and the blends. ENR did not affect thermal properties of EVA investigated by the differential scanning calorimetry. The X‐ray diffractometry showed discrepancy in degree of crystallinity before and after specimen stretching and after heat shrinking. It is believed that ENR particles decreased molecular orientation of EVA resulting in a decrease in degree of crystallinity but the remained orientation was sufficient for heat shrinking. The blend showed better extrudability than EVA after increasing take‐up speed. Therefore, the extruded tube prepared from the blend provided higher heat shrinkage than EVA tube. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009