DC Breakdown Performances of EP/TiO2 Nanocomposites at Elevated Temperatures Dominated by Carrier Traps and Molecular Chain Dynamic

DC breakdown is one of the underlying problems for epoxy (EP) based electrical power applications with elevated operating temperature. To investigate the breakdown mechanism at elevated temperature and improve DC breakdown strength for epoxy resin, functional nano-titania (TiO2) fillers were incorporated into epoxy matrix with four filler contents, and DC breakdown characteristics of EP/TiO
₂
nanocomposites were tested at four elevated temperatures, the trap characteristics were analyzed by TSC curves and a charge transport and molecular dynamic (CTMD) model was used to calculate the breakdown strength for pristine epoxy resin at elevated temperatures. It indicates that the incorporation of nano-fillers with optimal filler contents can effectively increase breakdown characteristics about 10
^%
for all temperatures, DC breakdown strength owns a positive relation with the deep trap level, which proves the carrier trap is the main factor determines the breakdown strength at the same temperature. While for the breakdown at different temperature, the breakdown strength decreases with temperature exponentially. An Arrhenius formula with activation energy of 0.15 eV is used to describe the relationship between molecular chain mobility and temperature for 1 wt% EP/TiO
₂
nanocomposites. In this case, the simulation breakdown strengths by CTMD model exhibits greatly accordance with experimental results, which indicate the breakdown characteristics at elevated temperatures are mainly controlled by molecular chain segment dynamics. The findings in this work provide a reliable path to improve DC breakdown strength for epoxy resin at elevated temperature by tailoring carrier traps and molecular chain dynamics.