Study on the ablative resistance properties of epoxy composites with nano/micro fillers for vacuum insulators

Ablation characteristics is a key factor in the surface flashover of insulation materials for vacuum insulators. The influence of nano/micro Al2O3 and Al(OH)3 fillers on the ablative resistance of epoxy vacuum insulation material has been investigated by repeated flashovers in vacuum under microsecond pulses. It was found that the ablative resistance of Al(OH)3 filler is much better than that of Al2O3 and that the nano-filler is more effective than the micro-filler in the case of Al(OH)3, whereas in Al2O3 the opposite applies. A thermal-electrical coupled 3-dimensional finite element simulation model has been developed to describe the results and analyze them in terms of the thermal characteristics of the particles. The model shows that although both Al2O3 and Al(OH)3 fillers can improve the ablative resistance of the epoxy composites, with Al(OH)3 being the better material. The mechanism whereby this occurs is different in the two cases, with the dehydration reaction dominating for Al(OH)3 and the mass degradation dominating for Al2O3.