Chemical, physical and microstructural properties of thermally aged XLPE cable models

The thermal aging of cross-linked polyethylene (XLPE) cable models has been investigated to obtain information on aging effects and mechanisms. After thermal life tests, XLPE cable models were subjected to chemical, physical, electrical and microstructural characterizations. The results of density, melting point and enthalpy, electrical conductivity and electric strength measurements, scanning electron microscopy observations, energy dispersive, and wavelength dispersive spectrometry microanalysis are presented and discussed. Remarkable changes of density, melting enthalpy, electrical conductivity and electric strength occur during thermal aging. Thermooxidative processes occur at the highest temperatures and times, which can be overcome at lower temperatures by postcuring reactions, not dangerous for the material behavior. At 100°C, degradation processes are not heavily involved; a thermal threshold close to this temperature can be therefore envisaged according to thermal life test results