Effects of Crosslink Coagent on the Conductivity and Breakdown strength of XLPE

Abstract

Cross-linked polyethylene (XLPE) has been widely used as insulation material in power cables. However, in order to ensure sufficient crosslinking degree of insulation, the content of peroxide initiator in the material component is excessively high in some cases, which leads to a large number of byproducts in the crosslinking process. Some of these crosslinking by-products cannot be removed through the degassing process, resulting in impurities and micropores in the cable insulation, and this may threaten the long-term operation of the cable. In order to reduce the content of peroxide initiator, trimethylolpropane trimethacrylate (TMPTMA) was selected as a coagent for crosslinking. The thermal elongation results indicate that under the similar thermo-mechanical stability, DCP dosage can be reduced to from 2.0 phr to 1.6 phr by using 0.3 phr TMPTMA And by adding 0.5 phr TMPTMA, the DCP dosage can be reduced to 1.4 phr. The infrared spectroscopy results prove that TMPTMA have been grafted onto XLPE molecules during crosslinking. The electrical conductivity results show that after the introduction of TMPTMA, the conductivity of modified XLPE has been decreased significantly and the temperature dependence of conductivity of XLPE is obviously suppressed. Besides, the XLPE-TMPTMA materials exhibit evidently higher DC breakdown strength than XLPE.