A mechanistic kinetic model, based on the reaction of primary and secondary amine functionalities with an epoxy-hydroxyl complex, combined with the occurrence of other equilibrium complexes has been developed by using the complementary information from the nonreversing heat flow and heat capacity from modulated temperature DSC (MTDSC). The model allows for reaction kinetics simulation of the unmodified epoxy-amine systems diglycidyl ether of bisphenol A (DGEBA) + aniline and DGEBA + methylenedianiline (MDA). To simulate the effect of the polymeric modifiers poly(ether sulfone) (PES: T-g = 223 degreesC) and poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (triblock: T-g = -70 degreesC) on the reaction rate, an additional complex has to be considered between the ether groups of these modifiers and the hydroxyl groups formed. The high interdiffusion rates at the onset of reaction-induced phase separation in the case of the triblock modifier result in a distinct rate increase, which can be predicted on the basis of information about the composition and fraction of the coexisting phases.