Effect of gamma-ray irradiation on permittivity and dielectric loss of polymer insulating materials

The effect of gamma-ray irradiation on relative permittivity, ac conductivity and dielectric loss tangent of epoxy resin and polyethylene has been investigated. Laminated samples were irradiated by ⁶⁰Co gamma source at room temperature in air with a dose rate of 10 kGy/h and the total dose were 100 kGy and 1000 kGy. The dielectric properties were measured by using a Precision LCR Meter (Agilent E4980A) with frequency range between 0.5 kHz and 2 MHz. FTIR spectrum as well as DSC curve for the each sample was also measured to understand the change in physical or chemical structure induced by the irradiation. Obtained results show the dependence of the dielectric properties upon the total dose which is varied with the material. It is suggested that the change in the dielectric properties is due to gamma-ray irradiation induced chemical reactions which result in the variation of material structure.