Thermogravimetric analysis was used to predict the lifetime of two three-component systems of diglycidyl ether of bisphenol A (n = 0)/1,2-diamine cyclohexane [DGEBA (n = 0)/1,2-DCH] modified with different concentrations of an epoxy reactive diluent, vinylcyclohexene dioxide (VCHD). Experimental results were treated using two methods. The first method was independent of the degradation mechanism, and the second was based on the thermodegradation kinetic mechanism. The activation energies of the reaction were determined using the Flynn-Wall-Ozawa method. These values were compared with those obtained using Kissinger's method. From experimental results it was found that the optimum temperature of service for these materials were different, so one or the other must be selected, depending on the application temperature considered. (C) 2003 Wiley Periodicals, Inc.