In this paper, the high purity bisphenol-A diglycidyl ether (DGEBA) epoxy resin (D.E.R 332), which is mainly used as filament winding, electrical laminates and encapsulation applications, was used as a host. The epoxy resins were loaded with nano-SiO2 and nano-BN in different loading concentrations, and then test of the AC/DC breakdown strength has been performed. It has been observed that the presence of untreated nano-fillers will decrease the AC/DC breakdown strength of nanocomposites. This may be caused by field enhancement resulting from agglomeration of un-treated nano-fillers. The influence of filler concentration and surface treatment, especially the filler type, of particles on AC, DC breakdown strength and space charge has been investigated. Moreover, it has been widely recognised that the presence of moisture in nanocomposites has detrimental effect on the electrical performance. Therefore, the water absorption of epoxy nanocomposites and its impact on electrical performance has also been considered.
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