Space charge formation related to the morphology of polymers

The technique of thermally stimulated depolarization current measurements (TSD) was used successfully to investigate temperature-dependent space-charge formation of nonpolar polymers. In polypropylene sheet samples, the relaxation peak at crystallite melting temperature is related to the separation of stored charge carriers from the helix molecules forming the crystalline phase. The method of thermally stimulated infrared spectroscopy was used to reveal structural relaxations comparable to those found using TSD. Space-charge decay at temperatures below melting point seems to be connected to the relaxation of the helices embedded in the amorphous regions. Observing the trace of a growing electrical tree confirms that charge carriers are stored mainly at structural interfaces (amorphous regions), causing a privileged direction for an electrical breakdown.<
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