Thermal Annealing on the Thermal Performance of XLPE from Retired Cables

Abstract

In the present paper, different annealing methods were performed on cross-linked polyethylene (XLPE) from three retired cables, the effects on thermal performance were discussed. The cables with length of 15 cm were prepared and the insulation layers were peeled, and the peels near the inner semi-conductive layer were used as the test samples. Isothermal treatment and heat recycling treatment were performed on the samples at temperatures of 85, 90, 95, and 100°C, and the temperature holding hour Th in the heat recycling treatment were 8, 16, and 24 h. Each kind of heat treatment was repeated 20 times, and the duration of the isothermal treatment was the same as that for the heat recycling treatment with 24 h temperature holding hour. Then, differential scanning calorimetry (DSC) were performed. The results show that the melting point, crystallinity, lamellar thickness increase and melting range decreases as the annealing temperature increases; the optimal values appear as the samples were annealed at 95°C. With longer Th, the cables annealed at 95°C exhibit decreased melting range and increased crystallinity, melting point, lamellar thickness.