Thermal Decomposition Properties of Epoxy Resin in SF₆/N₂ Mixture.

As a promising alternative for pure SF6, the mixture of SF6/N-2 appears to be more economic and environment-friendly on the premise of maintaining similar dielectric properties with pure SF6. But less attention has been paid to the thermal properties of an SF6/N-2 mixture, especially with insulation materials overheating happening simultaneously. In this paper, thermal decomposition properties of epoxy resin in SF6/N-2 mixture with different SF6 volume rates were studied, and the concentrations of characteristic decomposition components were detected based on concentrations change of some characteristic gas components such as CO2, SO2, H2S, SOF2, and CF4. The results showed that thermal properties of 20% SF6/N-2 (volume fraction of SF6 is 20%) mixture has faster degradation than 40% SF6/N-2 mixture. As ratio of SF6 content decreases, thermal stability of the system decreases, and the decomposition process of SF6 is exacerbated. Moreover, a mathematical model was established to determine happening of partial overheating faults on the epoxy resin surface in SF6/N-2 mixture. Also thermal decomposition process of epoxy resin was simulated by the ReaxFF force field to reveal basic chemical reactions in terms of bond-breaking order, which further verified that CO2 and H2O produced during thermal decomposition of epoxy resin can intensify degradation of SF6 dielectric property.