Thermal degradation behavior and pyrolysis products of electrical-grade epoxy resins under extreme thermal conditions

Abstract The pyrolysis behaviour of three epoxy resin systems commonly used in electrical power equipment was comparatively investigated to elucidate structure-dependent degradation pathways and product evolution under extreme thermal conditions. Thermogravimetric analysis (TGA) combined with pyrolysis–gas chromatography–mass spectrometry (Py–GC/MS) revealed that curing structure strongly influences both thermal decomposition behaviour and volatile product distributions. The electrical-grade epoxy system exhibited predominantly olefinic and aliphatic fragments at intermediate temperatures, while the anhydride-cured resin generated oxygenated aromatic species such as phthalic anhydride, and the amine-cured epoxy preferentially produced phenolic compounds and higher solid residues. Bisphenol A (BPA) was consistently detected at elevated temperatures (≥600 °C) across all systems, indicating secondary degradation associated with aromatic epoxy networks. Kissinger kinetic analysis yielded global apparent activation energies in the range of 139–184 kJ·mol ⁻¹ , enabling a comparative assessment of thermal degradation tendencies among the epoxy systems. The results establish a clear structure–pathway–product relationship for electrical-grade epoxy resins and highlight the environmental relevance of their pyrolysis products in thermal fault and end-of-life treatment scenarios.