Abstract
The combination of chemical method and mass spectroscopy was useful for analyzing the curing process of epoxy resins by simultaneously determining epoxy, carboxyl, and hydroxyl groups, as well as gases evolved. The side reaction was found to take place, in which the epoxy group reacted with acrylic acid, derived in the course of curing from an oligomer used as a curing agent. The side reaction generated carboxylic acid, bringing hydrophilic property into the cured resins, thus resulting in the increase of moisture content. Unexpectedly, a sharp decrease of carboxylic acid on curing was found, when the mixture of epoxides and carboxylic acid reacted with dicyandiamide or isophthalic acid dihydrazide, widely used as a latent hardener for epoxy resins.
