Structure, shrinkability and thermal property correlations of ethylene vinyl acetate (EVA)/carboxylated nitrile rubber (XNBR) polymer blends

Heat shrinkability a collective property of polymers, is being utilized in various applications- mainly in the field of encapsulation. Elastic memory is introduced into the system in the form of an elastomeric phase and throu gh subsequent crosslinking. In this work, dicumyl peroxide (DCP) cured blen ds of ethylene vinyl acetate copolymer (EVA) and carboxylated nitrile rubbe r (XNBR) were studied with reference to their shrinkability and thermal beh avior. Shrinkability of the blends depends on the elastomer content, cure t ime and temperature. With increase in cure time the shrinkage was found to decrease. With increase in elastomer content shrinkability increased up to a certain level of elastomer content (50%) and then decreased. High tempera ture (HT) stretched samples showed higher shrinkage than room temperature ( RT) stretched samples. Blend compostion and degree of orientation control t he thermal stability of the blends. Increase in EVA (plastic) content i.e c rystallinity and increase in orientation of blends increased the thermal st ability. The values of heat of fusion were consistent with the values of pe rcent crystallinity. (C) 2000 Elsevier Science Ltd. All rights reserved.