Toughening Epoxy Resin for Low-Temperature Electrical Insulation in High Voltage Equipment

Epoxy resin in dry cable terminations suffers serious dielectric failure under low-temperature conditions, due to embrittlement-induced fracture toughness degradation and partial discharges. This work engineers epoxy-based composites by incorporating poly(methyl methacrylate)-block-poly(butyl acrylate)-block-poly(methyl methacrylate) (PMMA–b-PBA–b-PMMA) triblock copolymers that achieves 42% fracture toughness enhancement at -40°C, while preserving glass transition temperature (Tg> 117 °C) and stable dielectric performance. When the doping content is 20 wt%, the elongation at break increases from 2.54% to 5.49% at -40 °C, corresponding to a 116% increase. Dielectric loss measurements show that the modified samples maintain low loss values across the temperature range from -80 to 40 °C, confirming their suitability for low-temperature insulation applications. Under 14 kV AC voltage, optimized formulations exhibit 51% enhancement of partial discharge inception voltage and 260% extension of electrical tree breakdown time. These improvements are attributed to the formation of nanoscale domains, wherein PBA-rich regions absorb fracture energy via nanocavitation, and PMMA-rich regions restrict chain mobility and homogenize electric fields. This distinctive molecular architecture endows the epoxy composite with simultaneously enhanced low-temperature toughness and electrical insulation performance, demonstrating promising application potential in epoxy-based power equipment.