THE INFLUENCE OF CHEMICAL-STRUCTURE ON THE DIELECTRIC BEHAVIOR OF POLYPROPYLENE

An initial study has been made of radiation-induced oxidation of polyp ropylene (PP) in both its additive-free form and one containing discre te 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-irradi ation oxidation when the material was exposed to room air following ir radiation. Studies were made of the chemical structure of the material and its concomitant dielectric behavior in terms of loss at low frequ encies and thermally-stimulated discharge current (TSDC). The polar fu nctional groups induced via irradiation were observed to affect the di electric response of the material, with the introduction of HALS reduc ing the concentration of gamma-induced oxidation products and the magn itude of the corresponding electrical signals.