Dehydration reaction effect of metal hydroxide on AC voltage lifetime of epoxy composites.

In general, a polymer insulator to which high voltage is applied reaches a complete volume breakdown state through a propagation of electrical trees. A flame retardant such as metal hydroxide has an endothermic reaction and releases water at high temperature. If the energy of the partial discharge is consumed by a dehydration reaction, the growth length of electrical tree will be restrained and the polymer's insulator lifetime will improve. Therefore, we studied the effects of metal hydroxide on treeing under high electric fields and confirmed that the voltage lifetime of the epoxy resin with 30 phr of magnesium hydroxide was approximately 100 times longer than the neat epoxy resin. We also detected magnesium oxide by electron beam diffraction analysis of the fillers located contiguous to the electrical trees. The dehydration reaction of magnesium hydroxide took place. The suppression of tree growth by fillers is generally explained by a barrier effect, but such fillers as metal hydroxide that generated the dehydration reaction provide another mechanism for the restraint of tree growth. [ABSTRACT FROM AUTHOR]