The electrical–thermal transmission mechanism and performance optimization of microcapsule epoxy resin composites

Epoxy resin insulators easily develop microcracks in service, impairing insulation reliability. This study aims to investigate the effects of microcapsule particle size and spacing on the electrical and thermal properties of microcapsule/epoxy resin composites. Microcapsules with a stable core–shell structure were prepared via in situ polymerization, and a COMSOL-based finite element model was established combined with experimental validation. Key results show that decreasing microcapsule spacing from 180 to 10 μm sharply increases current density from 5.03 to 98.45 A/m2, while electrical conductivity stabilizes at ∼5.19 × 10−10 S/m. For thermal performance, increasing spacing from 10 to 180 μm raises conductive heat flux from 7398 to 12 956 W/m2, with optimal thermal conductivity near 0.2595 W/(m K) at ∼100 μm spacing. Larger particle sizes (10–40 μm) increase conductivity but reduce thermal conductivity. Self-healing tests show a healing rate of 85% at 10 wt. % microcapsules. In conclusion, optimal spacing for electrical performance is 20–100 μm (particle size 20–30 μm) and for thermal performance, 80–120 μm (particle size ≤20 μm). This study provides design guidance for self-healing insulating materials.