Effect of gamma-ray irradiation on the TSC in polyethersulfone

When polyethersulfone was irradiated by gamma rays and then poled at 37 degrees C, a new TSC (thermally stimulated current) peak appeared at similar to 100 degrees C. This new peak and other peaks near 40 and 150 degrees C increase with an increase in dose of similar to 0.6 kGy, and this is considered to be due to trapped charges and other ionic carriers becoming mobile when rearrangement of scissioned chains occurs. However, if the dose exceeds 0.6 kGy, the peak magnitude decreases. Furthermore, if the TSC was poled at 120 degrees C, only the peak near 150 degrees C appeared and this peak monotonically decreased with an increase in the irradiation dose. A similar decreasing tendency was also observed in the conduction current and in the residual voltage. These decreasing features are considered to be caused by the radiation-induced change that rearrangement of scissioned chains decreases free volume for ionic transport.