Thermally stimulated currents (TSC) of γ‐irradiated poly(methyl methacrylate) thermoelectrets have been investigated in the high‐temperature range. The two main peaks of the TSC spectrum, appearing, respectively, at about 100 (α) and 120°C (ρ), show marked differences in stability under irradiation: while the α peak is little affected by doses up to 10 7 rad, the ρ peak vanishes following doses of 10 5 to 10 6 rad. On the other hand, a study of the rate of decrease of the ρ peak as a function of irradiation conditions reveals the important role of the surrounding atmosphere and the existence of a flux effect, probably related to irradiation‐accelerated diffusion of gas into the polymer. All these facts confirm the respective attributions of α and ρ peaks to a dipolar volume polarization and to an ionic space charge polarization, showing that the TSC study of irradiated thermoelectrets can be a useful method for identification of polarization processes in polymers.
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Vanderschueren et al. (1978) studied this question.