No abstract

Heat shrinkability of the polymer, which depends on the elastic memory, is being utilized in various applications, mainly in the field of encapsulation. The elastic memory is introduced into the system in the form of an elastomeric phase. Here the blends of ethylene vinyl acetate and polyurethane were studied with reference to their shrinkability, introducing crosslinking in both the phases. It is found that with increase in elastomer content the shrinkage increased to a certain level and then decreased. With increase in cure time shrinkage is decreased. It is seen that high‐temperature (HT) stretched samples showed higher shrinkage than room temperature (RT) stretched one. Generally, the crystallinity of the HT stretched sample is higher than that of low‐temperature stretched sample, which is again higher than that of original sample. From high temperature differential scanning calorimetry it is found that with increase in PU content stability towards oxygen is increased and further high temperature processing decreases the initial degradation temperature but enhances the rate of degradation. From scanning electron microscopy it is seen that an HT stretched sample is more elongated than an RT stretched one. Copyright © 2000 John Wiley & Sons, Ltd.

Abstract-In this work, it has been attempted to characterize a new type of impedance sensor called constant phase element (CPE) sensor; which has microporous PMMA-film coating on the electrode surface. It has been shown that the 'constant phase angle (CPA)' behaviour is primarily due to the porous structure of the electrode surface. And the phase angle at the output of the sensor changes with thickness variation of the PMMA coating and ionic property of the medium in which the sensor is dipped in. The sensor has been used for chemical sensing.A phase angle detector circuit gives the output in voltage with the change in the phase angle.The complex impedance plots of the probes has also been discussed. The important fact is that the constructed CPE gives rise to a fractional order system.

Heat shrinkability, which is 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. Here the blends of ethylene vinyl acetate and chlorosulfonated rubber were studied with reference to their shrinkability. It was found that an increase in the elastomer content increased the shrinkage and an increase in cure time also increased the shrinkage. It was seen that high temperature (H‐T) stretched samples showed higher shrinkage than the low (room) temperature (R‐T) stretched one. Generally, the crystallinity of the H‐T stretched sample was higher than that of the low temperature stretched sample, which was again higher than that of the original unstretched sample; but for the low elastomer content blend the crystallinity of the R‐T stretched sample was found to be greater than the corresponding H‐T stretched one. The H‐T differential scanning calorimetry showed that an increase in the CSM content caused the stability toward oxygen to increase. The first decomposition temperatures were found to be higher and the second decomposition temperatures appeared to be lower for the H‐T shrunk sample than the corresponding unstretched sample. The rate of degradation appeared to be enhanced initially, then after 50% decomposition the rate started going down compared to the usual unstretched sample. From SEM it was seen that the H‐T stretched sample was more elongated than the R‐T stretched one. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 707–715, 2000

No abstract