A NEW APPROACH TO MODELING THE CURE KINETICS OF EPOXY AMINE THERMOSETTING RESINS .2. APPLICATION TO A TYPICAL SYSTEM BASED ON BIS[4-(DIGLYCIDYLAMINO)PHENYL]METHANE AND BIS(4-AMINOPHENYL) SULFONE

Differential scanning calorimetry in dynamic and isothermal modes was used to study the cure kinetics of the commercial epoxy system Narmco 5208, whose main components are bis[4-(diglycidylamino)phenyl]methane and bis(4-aminophenyl) sulfone. The data were analyzed in terms of a new mechanistic approach described in the preceding paper. The treatment explicitly takes into account both the epoxide-amine reactions and the subsequent etherification reaction. The kinetics can be completely described in terms of three rate constants, which obey the Arrhenius relationship. Excellent agreement with the experimental data is obtained if the etherification reaction is assumed to be first order with respect to the concentrations of epoxide groups, hydroxyl groups, and the tertiary amine groups formed in the epoxide-amine reaction. This model applies over the whole range of conversion up to the point where the resin vitrifies and the reaction becomes diffusion-controlled. The effect of the diffusion control is described very well by an approach based on simple equations proposed in the literature. Altogether, the model allows accurate prediction of the degree of conversion over the whole range of cure and over the temperature range 160-200-degrees-C, which covers the usual curing conditions. Although the rate constants derived are specific to Narmco 5208, the model itself is generally applicable to other epoxy amine systems.