DSC measurements on XLPE cables at low and high heating/cooling rates

The authors present preliminary DSC (differential scanning calorimetry) results obtained on XLPE (cross-linked polyethylene) cable insulation at low and high rates of heating/cooling for unaged and electrically aged samples characterized in terms of their birefringence pattern. Some measurements were made under dry conditions while some results are presented for samples in cyclopentane. The DSC measurements at 3-6 K/h (0.05-0.1 K/min) heating/cooling rate show a reversible endotherm above the melt temperature of the orthorhombic phase. This post-melting peak cannot be observed at the conventional DSC heating/cooling rate of 6-10 K/min but it is observable at lower temperatures when the XLPE samples are put in cyclopentane. The effects are associated with order-disorder transitions in strained networks.< >