Cure kinetics for bisphenol a resin with zinc naphthanate accelerator

We have investigated the cure kinetics of the popularly used electrical insulating epoxy system for high voltage rotating machines, consisting of diglycidyl ether of bisphenol A (DGEBA) and methyl hexahydro-phthalic anhydride (MHHPA), when used with a zinc naphthenate (ZnN) accelerator. By using a range of analytical tools, especially the complimentarily afforded by combining thermal and spectroscopic methods, we have obtained the major kinetic parameters of the cure that encompass the behavior from an uncured to an almost fully-cured state. All our experiments show that ZnN accelerated systems do not go to full cure, and the exotherm is considerably lower than that seen with tertiary ethyl ammonium bromide (TEAB). This suggests that the cured state must have fewer cross-links, and hence be somewhat more flexible than in the TEAB case.