Cure Kinetics of Commercial Epoxy-Amine Products with Iso-Conversional Methods

The dependence of the apparent activation energy for the epoxy-amine reaction on the degree of conversion can be obtained by applying iso-conversional methods to the non-isothermal cure data obtained by using differential scanning calorimetry (DSC). The application of three iso-conversional methods has been utilized for the analysis of non-isothermal DSC cure data for three commercial high solids epoxy-amine coatings. The average apparent activation energy for cure of the fully formulated commercial product(s) is very similar to that previously reported for the epoxy-amine clear coats, indicating that the presence of additives does not influence the epoxy-amine apparent activation energy. Among the methods tested, Friedman’s method performed the best in fitting the experimental DSC data. In addition, all three methods underpredict the experimental isothermal cure data for three commercial products at two different cure conditions (i.e., 23 °C/50% RH and 40 °C/70% RH), showing that the non-isothermal DSC experiments cannot capture the catalytic effect of water on the curing reaction of epoxy-amine coatings. Furthermore, for high-solids epoxy-amine products, at least 60% conversion is required to achieve the time when the applied coating will not show any tackiness (i.e., the T2 time measured using the Beck Koller method).