Self-repair environmentally friendly insulation material based on disulfide bond and DA reaction

Cross-linked polyethylene (XLPE) is widely used in high-voltage cable insulation for its good insulation and mechanical properties. However, long-term use leads to damage, breakdown, and environmental pollution due to non-recyclability and high thermal degradation. This study designs an S-S-DA cross-linker with reversible Diels-Alder (DA) and disulfide bonds using isocyanate reactions. Graft cross-linking forms XLPE-S-S-DA, and doping silane-modified SiO₂ creates XLPE-S-S-DA/SiO₂ composite for self-repair. Tests show elongation at break increases by 17.89%, tensile yield stress by 17.26%, and breakdown field strength by 34.4% compared to XLPE. It self-repairs mechanical/electrical damages (three mechanical repairs restore strain to 91.26%, yield stress to 82.65%, strength to 92.37%; three breakdowns restore field strength to 76.04%). Three recycling retains 68.89% strain, 71.59% strength (yield stress increases 6.46%), and 79.57% breakdown strength. Lower thermal degradation helps recycling. Dynamic cross-linking and doping create self-repair, recyclable XLPE composites, improving service life and eco-friendliness for high-voltage cable insulation, providing a new design strategy.