A comparative study of dielectric, mechanical and structural properties of fire-protective insulation based on XLPE

Paper deals with comparing of dielectric, mechanical and structural properties of primary cable insulation based on cross-linked low density polyethylene (XLPE) with different level of cross-linking. Testing material was divided into four groups according to time of exposition to low pressure steam, which initiates cross-linking reaction. The measurement of the degree of cross-linking by chemical extraction in xylene solution at 140 °C according to ASTM D2795–11 followed. Dielectric properties (polarization index, volume resistivity) of the individual samples were then measured according to standards. Dielectric properties were compared with results of tensile strength test at various temperatures (50 °C, 55 °C, 60 °C) measured by dynamic mechanical analysis. The degree of cross-linking represented by the gel content positively influences the tensile strength, the volume resistivity and the change of structural behaviour of the material by differential scanning calorimetry was also observed. But it negatively affects the polarization indexes. Changing measured parameters could be explained by the change of the reaction dynamics in accordance with the time of exposition which initiate cross-linking reactions.