Significantly enhanced DC breakdown strength and high-temperature resistivity of cross-linked polyethylene through alloying polystyrene strategy

Abstract

Developing a stable insulation material stands as a crucial challenge for high-voltage direct current (HVDC) cable insulation. This work proposes an alloying strategy to significantly enhance the breakdown strength and high-temperature resistivity of cross-linked polyethylene (XLPE). The strategy involves blending low-density polyethylene (LDPE) with polystyrene (PS), resulting in a polymeric alloy. Confirmation of PS alloying within XLPE is supported by observed shifts in polyethylene miller indices (110) and (200) planes. The dicumyl peroxide used as a crosslinking agent demonstrates an ideal 1.41% enhancement in LDPE-PS crosslinking. The integration of aromatic ethers in the cross-linked network enhances temperature stability. Alloying PS at 220°C in XLPE leads to improved inter-molecular interactions and increased interfacial area, creating a sea–island morphology that resolves voids and limits defect or crack propagation by forming additional trapping sites. The enhanced breakdown strength and reduced conductivity of XLPE-PS are attributed to increased deep trapping sites and reduced carrier mobility resulting from alloying. The reduced conductivity at 70°C and 90°C demonstrates stability under electric fields. Remarkable breakdown strength improvements of 27.5% and 23.6% are observed at 30°C and 50°C. The proposed alloying strategy suggests replacing XLPE with advanced XLPE-PS, offering promising prospects for HVDC insulation.