KINETICS OF ANHYDRIDE CURING OF ISOPHTHALIC DIGLYCIDYL ESTER USING DIFFERENTIAL SCANNING CALORIMETRY

The cure reaction of a model diglycidyl ester, bis- (2,3-epoxypropyl) - 1,3-benzenedicarboxylate, with hexahydrophthalic anhydride as the curing agent and benzyldimethylamine as the catalyst, was studied by differential scanning calorimetry using an isothermal approach over the temperature range 100-135-degrees-C. The results indicate that the cure reaction is autocatalytic in nature and does not follow simple nth-order kinetics. A semiempirical equation for autocatalytic systems containing two rate constants and two reaction orders, viz., 0.5 and 1.5, provided a good phenomenological description of the cure kinetics up to the point of vitrification. With the inclusion of a diffusion factor into this model, it was, however, possible to predict with precision the cure kinetics over the whole range of conversion covering both pre- and postvitrification stages and over the entire temperature range of 100-135-degrees-C employed for isothermal curing.