Influence of gamma radiation on the properties of polyethylenenapthalate (PEN)

Foil samples of polyethylenenapthalate, 25 μm. thick have been subjected to radiation doses of 26.5 and 158.4 kGy from a ⁶⁰Co source to promote ageing. The current transients produced by the application and removal of a DC voltage to the samples were measured over an extended period of time. Peaks in both the charging and discharge currents were observed whose positions were dependent on both temperature and radiation dose. Activation energies were obtained from isochronal charging currents and from the frequency domain. These showed a dose dependence. Curve fitting to the initial discharge transient and to the dielectric loss peak in the frequency domain indicated that the ageing had not produced changes in the type of loss mechanisms. A linear relationship was found between the received dose and the dielectric loss peak position.