Kinetics analysis and simulation of sequential epoxy dual-curing systems with independent thermal activation

Abstract

The curing kinetics of a sequential dual-curing system based on an off-stoichiometric amine-epoxy formulation with intermediate latent reactivity has been analyzed. The first curing stage is an epoxy-amine polycondensation taking place at low temperatures, while the second curing stage is an anionic homopolymerization of the excess epoxy groups, taking place at high temperatures and catalyzed by a latent base. The different reactivity of both polymerization processes allows an excellent separation into well-defined curing stages each of which can be analyzed individually. The kinetics of the two curing stages have been analyzed by integral isoconversional procedures and model-fitting methods. Both methodologies successfully simulated each curing stage and also the global curing process, showing that it is possible to control the activation of both curing stages. Isoconversional integral analysis is a simple yet powerful method that can be used for the simulation of temperature-controlled curing programmes. Model-fitting analysis is more suitable for the flexible simulation of processing scenarios such as the curing of composites.