Hm. Banford et al., THE INFLUENCE OF CHEMICAL-STRUCTURE ON THE DIELECTRIC BEHAVIOR OF POLYPROPYLENE, IEEE transactions on dielectrics and electrical insulation, 3(4), 1996, pp. 594-598
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.