Dielectric breakdown characteristics of DGEBA/MDA/SN-Al/sub 2/O/sub 3/ composite system

The dielectric breakdown characteristics of Al/sub 2/O/sub 3/ filled DGEBA (diglycidyl ether of bisphenol A)/MDA (4,4'-methylene dianilene/SN (succinonitrile) system were investigated. To simulate the stress concentration the sharp-pointed needle and plane electrode geometry was used. It was shown that as the filler contents increased the dielectric breakdown strength increased and then decreased at higher filler content than 5 phr because of the increment of weak point, especially at the interface of filler and epoxy resin initiated from the weakest point of the needle electrode tip. To increase the resistance to the higher electrical stress the curing condition should be modified and a new coupling agent should be introduced.