Effect of γ-ray irradiation on the thermally stimulated current in polyethersulfone

Effect of γ-ray irradiation on the charge behavior of polyethersulfone (PES) is investigated through the measurement of thermally stimulated current (TSC). Each sample is irradiated by γ-rays in air at room temperature to various total doses less than 30 kGy. In the TSC spectra obtained after a poling process at 37 °C, β peak at 150 °C increases first with an increase in the dose up to 0.61 kGy, and then decreases. The γ peak which is not observed in the non-irradiated sample appears at 100 °C in the irradiated sample. Similarly to the β peak, the γ peak increases in the low dose region and decreases if the irradiation dose exceeds 1 kGy. When the sample is poled at 120 °C, the γ peak is not observed and the β peak decreases monotonically as the dose Increases. It is considered that scission of polymer main chains occurs during the γ-ray irradiation and that rearrangement of main chains from a loose packing to a more rigid packing occurs while the sample is heated during the TSC measurement. This molecular rearrangement is considered to be the origin of the γ peak and also related to the decrease of the charge quantity of TSC.