Surface charging and charge decay on gamma-ray irradiated Epoxy resin laminate

Epoxy resin (EX) laminate was employed as test sample to investigate the effect of gamma-ray irradiation on dynamic behavior of surface charging and charge decay. Prior to the test, the samples were irradiated in air up to 100 kGy and then up to 1000 kGy with dosage rate of 10 kGy / h by using a ⁶⁰Co gamma-source. The experiment was carried out at room temperature with relative humidity of ~ 50%. The sample surface was corona charged by applying a dc voltage of -4 kV between needle-plate electrodes. An electrostatic voltmeter was employed to measure the surface charge. Obtained results show the dependence of the behavior of surface charging and charge decay upon the radiation dose. With the increase of the radiation dose, max density and total amount of accumulated charge decrease, however, rate of charge decay appears to increase. It is suggested that the surface charge behavior depends upon the characteristics of localized surface states which is altered by the radiation induced cross-linking and degradation reactions of the polymer.