Crosslinking of an epoxy with a mixed amine as a function of stoichiometry. I. Cure kinetics via dynamic mechanical spectroscopy

Variation of the epoxy/curing agent ratio by as much as ±10 wt% from the stoichiometric ratio for a system containing a diglycidyl ether of bisphenol‐A (DGEBA) and a mixed aromatic amine was found to have a significant effect on the cure kinetics as determined by dynamic mechanical measurements. A sample preparation technique was developed for monitoring the cure of glass reinforced epoxy in flexure. Shear measurements were also made on the neat resin. From gel time flexural data, the activation energy of cure passed through a maximum at the stoichiometric ratio of epoxy/amine for a glass cloth composite. In shear for the neat resin, a minimum was observed. By considering the curing of the mixed system to follow third‐order kinetics, overall reaction rate constants were estimated after the gel point.