Shrinkability of ethylene vinyl acetate/polyurethane blends and their characterization

Heat shrinkability of the polymer, which depends on the elastic memory, is being utilized in various applications, mainly in the field of encapsulatio n. The elastic memory is introduced into the system in the form of an elast omeric phase. Here the blends of ethylene vinyl acetate and polyurethane we re studied with reference to their shrinkability, introducing crosslinking in both the phases. If is found that with increase in elastomer content the shrinkage increased to a certain level and then decreased. With increase i n cure time shrinkage is decreased. It is seen that high-temperature (HT) s tretched samples showed higher shrinkage than room temperature (RT) stretch ed one. Generally, the crystallinity of the HT stretched sample is higher t han that of low-temperature stretched sample, which is again higher than th at of original sample. From high temperature differential scanning calorime try if is found that with increase in PU content stability towards oxygen i s increased and further high temperature processing decreases the initial d egradation temperature but enhances the rate of degradation. From scanning electron microscopy if is seen that an HT stretched sample is more elongate d than an RT stretched one. Copyright (C) 2000 John Wiley & Sons, Ltd.