Influence of physical aging processes on electrical properties of polymers

The influence of aging temperature and time on the electrical properties of amorphous polydiancarbonate (PC) and poly(methyl methacrylate) (PMMA) was investigated using the techniques of thermally stimulated depolarization currents, transient currents, and AC dielectric losses. It is shown that in the temperature range located between the alpha relaxation (glass transition) and the secondary beta relaxation, the polarization and loss properties of amorphous polymers undergo pronounced changes during physical aging. A progressive decrease in molecular mobility (and corresponding increase in relaxation times) leads to a marked decrease in polarization and dielectric losses as a function of aging time, showing that physical aging is a general phenomenon which should not be ignored in any testing of electrical properties of plastics.<
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