Cure rates of some epoxy systems

The property changes of Epon 828 crosslinked by either diethylenetriamine or m‐phenylenediamine at several temperatures have been studied by two in situ techniques. The mechanical property changes were followed by continuously monitoring the changes in the fundamental frequency of vibration during cure of a resin‐coated substrate acting as a cantilever reed. The disappearance of the reactive epoxy group was followed in situ by continuously monitoring the absorbance of the infrared epoxide band at 915 cm.−1. Correlation of the two techniques was accomplished by normalizing both the mechanical property and infrared data. The apparent energy of activation was calculated to be 10.4 and 11.4 kcal. /mole, respectively, for the m‐phenylenediamine and diethylenetriamine systems by the mechanical technique, and 11.0 kcal./mole for the m‐phenylenediamine crosslinked system by the infrared technique.