A Dielectric Study of Oxidation in the Amorphous and Crystalline Regions of Low Density Polyethylene with Antioxidant

Abstract

The effect of antioxidant on oxidation both in the amorphous and crystalline regions of low density polyethylene (PE) was investigated. Degradation was carried out by oxidation using thermal aging below the melting point of PE subsequent to γ-irradiation. Dielectric measurement was carried out to compare the oxidation in the amorphous region and that in the crystalline. It was found that the antioxidants had little effect on oxidation in the crystalline region, though the oxidation in the amorphous region was suppressed by antioxidant. This is interpreted in terms of dispersion of the antioxidant in PE, which is suggested by DTA study. The degree of oxidation in the crystalline region was nearly the same as that in the amorphous region if the antioxidant was doped at a higher level than a certain value. This can be interpreted as resulting from the suppression of autoxidation by virtue of the antioxidant in the amorphous region and by the insufficient supply of oxygen in the crystalline region.