The influence of chemical structure on the dielectric behavior of polypropylene

An initial study has been made of radiation-induced oxidation of polypropylene (PP) in both its additive-free form and one containing discrete amounts of stabilizer (HALS). Samples of PP were irradiated in a Co-80 gamma source to various doses. This took place in either room air to give in-source oxidation or in vacuum at 77 K to render post-irradiation oxidation when the material was exposed to room air following irradiation. Studies were made of the chemical structure of the material and its concomitant dielectric behavior in terms of loss at low frequencies and thermally-stimulated discharge current (TSDC). The polar functional groups induced via irradiation were observed to affect the dielectric response of the material, with the introduction of HALS reducing the concentration of gamma-induced oxidation products and the magnitude of the corresponding electrical signals