KINETICS MODELING AND TIME-TEMPERATURE-TRANSFORMATION DIAGRAM OF MICROWAVE AND THERMAL CURE OF EPOXY-RESINS

Stoichiometric mixtures of a diglycidyl ether of bisphenol A (DGEBA)/d iaminodiphenyl sulfone (DDS) and a DGEBA/meta phenylene diamine (mPDA) were cured using both microwave and thermal energy. Fourier transform infrared (FTIR) was used for the measurement of the extent of cure an d thermal mechanical analysis (TMA) was used for the determination of the glass transition temperature (T(g)). The cure kinetics of the DGEB A/mPDA and DGEBA/DDS systems were described by an autocatalytic kineti c model up to vitrification in both the microwave and thermal cure. Fo r the DGEBA/mPDA system, the reaction rate constants of the primary am ine-epoxy reaction are equal to those of the secondary amine-epoxy rea ction, and the etherification reaction is negligible for both microwav e and thermal cure. For the DGEBA/DDS system, the reaction rate consta nts of the primary amine-epoxy reaction are greater than those of the secondary amine-epoxy reaction and the etherification reaction is only negligible at low cure temperatures for both microwave and thermal cu re. Microwave radiation decreases the reaction rate constant ratio of the secondary amine-epoxy reaction to the primary amine-epxy reaction and the ratio of the etherification reaction to the primary amine-epox y reaction. T(g) data were fitted to the DiBenedetto model. A master c urve and a time-temperature-transformation (TTT) diagram were construc ted. The vitrification time is shorter in microwave cure than in therm al cure, especially at higher isothermal cure temperatures. For the DG EBA/mPDA system, the minimum vitrification time is two to five times s horter in the microwave cure than in the thermal cure. For the DGEBA/D DS system, the minimum vitrification time is 44 times shorter in the m icrowave cure than in the thermal cure.