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Kinetic study and time‐temperature‐transformation cure diagram for an epoxy‐diamine system

The different steps involved in the curing reaction of a purified ether of bisphenol A (BADGE n = 0) and 1,2-diamine cyclohexane (DCH) were studied with the objective to calculate a time-temperature-transformation (TTT) isothermal cure diagram for this system. A kinetic model proposed by Horie et al. 6 was used and compared to the experimental data. Gelation times and conversions were measured using two different methods: solubility test and dynamic mechanical analysis (DMA). Results obtained by both methods show a reasonable agreement. Differential scanning calorimetry (DSC) data show a one-to-one relationship between T g and fractional conversion, α, independent of cure temperature. As a consequence, T g can be used as a measure of conversion. Using the model parameters and the relationship between T g and conversion, T g versus In time are calculated and found to agree with DSC experimental results for isothermal cure temperatures from 60 to 100°C. A kinetically controlled master curve for isothermal cure is obtained by shifting T g versus In time data to a reference temperature, T r = 80°C. The apparent activation energy was calculated from gel times measurements (12.63 kcal mol -1 = 52.88 kJ mol -1 from solubility test and 12.28 kcal mol -1 = 51.42 kJ mol -1 from DMA measurements). Isoconversion contours were calculated by numerical integration of the kinetic model.