Influence of antioxidants on electrical conduction in LDPE and XLPE

In order to study the effect of antioxidants on high-field electrical conduction of cross-linked polyethylene (XLPE), measurements were made of conduction currents flowing in XLPE specimens containing phenolic and sulfur-type antioxidants. Currents flowing in XLPE insulation containing these antioxidants were found to be less than those flowing in XLPE containing no antioxidants. The smallest detected current occurred in XLPE insulation containing the sulfur-type antioxidant dilauryl thiodipropionate, whereas larger currents were detected in XLPE containing phenolic antioxidants. It was also found that the magnitude of conduction current in XLPE samples containing the sulfur-type antioxidant depended on the concentration of the added antioxidant. The degree of measured crystallinity of XLPE was also found to be less than that of low-density polyethylene (LDPE), while the crystallinity was not found to be influenced by added antioxidants.