AN INFRARED SPECTROSCOPIC INVESTIGATION OF THE CURING REACTIONS OF THE EPON-828 META-PHENYLENEDIAMINE SYSTEM

Mid- and near-infrared (IR) spectroscopy has been used to study the curing of a bisphenol-A based epoxy resin (EPON-828) with a tetrafunctional curing agent, viz. , meta-phenylenediamine (MPDA). Three different cure cycles were used in the study. Primary amine functionality was observed to react relatively rapidly; none remained after curing for 2 h at 75 degree C. Secondary amine functionality was exhausted in epoxy rich samples subjected to the standard cure cycle (2 h at 75 degree C followed by 2 h at 125 degree C). In samples with stoichiometric amount or higher MPDA, complete reaction of secondary amine or epoxy groups was not observed. In amine-rich samples subjected to post curing (6 h at 175 degree C), evidence was seen for the reaction of hydroxyl and epoxy groups, resulting in a considerable increase in the crosslink density of these samples.