Radiation effects on dielectric properties of polymer films

With the development of space and nuclear technology, more and more polymers are used as structural and insulating materials in radiation circumstances. The variations of polymeric materials during and/or after the irradiation are widely studied by researchers. Dielectric properties of gamma-ray irradiated polymer films are measured and analysed in this paper. It is found that relative permittivity keeps almost constant with the absorbed dose and increases slightly as the dose exceeds 1*10⁵ Gy for both PET and PI films. The dissipation factor of irradiated PET films increases with the dose rapidly while that of PI films shows slight decrease at the beginning of radiation. Connecting these results with the microstructure changes of polymers, we know that the chain scissions, bond cleavages and the generation of radicals are the origin of the property changes. This paper also gives the guidance for the engineering application of PET and PI films in radiation occasions