Catalyst‐Regulated Chain Extension and Curing Processes for Tailoring Cross‐Linked Networks and Properties of Epoxy Resins for Electrical Insulation

ABSTRACT For ultra‐high‐voltage thick‐section epoxy insulation, reducing curing exotherm without compromising comprehensive performance remains a major challenge. This challenge is closely associated with the molecular architecture developed during chain extension and the cross‐linked network formed during subsequent curing. Herein, two commonly used chain‐extension catalysts, triethylbenzylammonium chloride (TEBAC) and triphenylphosphine (PPh 3 ), were systematically investigated to clarify their roles throughout the chain‐extension and curing process. TEBAC promotes the further reaction of secondary hydroxyl groups, producing a moderately branched molecular architecture while maintaining a low epoxy value of 0.30 eq/100 g. During subsequent curing, TEBAC exhibits a lower apparent activation energy and lower curing‐temperature range than PPh 3 , favoring a higher degree of curing under identical conditions. Consequently, the mEP/TEBAC system exhibits substantially improved overall performance compared with the commercial epoxy resin, with impact strength, glass transition temperature, and volume resistivity increased from 13.97 to 29.82 kJ m −2 , 111.6°C to 130.4°C, and 0.55 × 10 17 to 1.08 × 10 17 Ω cm, respectively. These results demonstrate that chain‐extension catalysts can influence not only the molecular architecture formed during chain extension but also the subsequent curing behavior, establishing a direct link between catalyst selection, molecular structure, curing process, and final properties.