CHARACTERIZATION AND DEGRADATION STUDIES OF PEROXIDE AND SILANE CROSS-LINKED POLYETHYLENE

Crosslinked polyethylene (XLPE) used as an insulation material is increasingly employed in aerial bundle cable systems for domestic power supply. This has resulted in the need to investigate the long term performance and properties of the polymer under thermal and UV ageing conditions. In the current study it has been attempted to characterise various silane and peroxide crosslinked low density polyethylene samples and to investigate the fundamental processes occurring during the thermal and UV degradation of these materials. The technique of solvent extraction used to determine the gel content and solvent swelling of the XLPE was shown to be ideally suited to characterise and to monitor the degradation of the XLPE. The two materials differ in relation to the mechanical properties, melting characteristics and network properties of the XLPE, with silane XLPE being generally less homogeneously crosslinked than peroxide XLPE. Various degradation studies revealed that this fundamental difference may also influence the mechanism of the degradation. Silane XLPE was shown to be more sensitive to the degradation and may degrade in a more heterogeneous manner than the peroxide XLPE.