Highly Controlled Charge Transport Achieved in Crosslinked Polyethylene-Polystyrene Polymeric Alloy Composite for High Voltage Direct Current Cable Insulation

Reliable high-voltage direct current (HVDC) cable insulation requires suppressed DC conductivity and stable charge transport at elevated temperatures. This study investigates charge transport mechanisms in crosslinked polyethylene-polystyrene (XLPE-PS) polymeric alloys, emphasizing the effects of structural evolution from unalloyed to alloyed states. XLPE-PS composites were prepared via controlled processing at 150°C (unalloyed) and 220°C (polymeric alloy), and DC conduction was measured over 30°C–90°C and 10–60 kV/mm using a three-terminal electrode system. Thermally stimulated depolarization current (TSDC) analysis shows that molecular-level dispersion of PS and enhanced interfacial crosslinking redistribute trap states, reduce space-charge accumulation, and stabilize carrier trapping/detrapping dynamics. As a result, charge transport in XLPE-PS transitions from hopping conduction at low fields, to space-charge-limited conduction over intermediate ranges, and to Poole-Frenkel conduction only under combined high field and temperature. Compared with conventional XLPE, the polymeric alloy exhibits significantly reduced DC conductivity and enhanced electrical stability. The mechanism map developed here links microstructural modifications, trap regulation, and conduction behavior, providing a rational framework for designing next-generation HVDC cable insulation with superior performance.