The effects of competitive primary and secondary amine reactivity on the structural evolution and properties of an epoxy thermoset resin during cure: A molecular dynamics study

Epoxy thermoset resins are widely used in industry due to their favorable thermomechanical properties. These properties depend strongly on the resin network topology formed during cure. In the past, there has been significant work to develop methodologies that simulate the cure process to predict the thermoset network topology and the properties of that network. However, very few of these simulations include anything more than a distance based criteria when determining which species in the simulation will bond. In this work, we show the importance of including additional bonding criteria based on the reaction kinetics for the system of interest. We simulate the cure of a model epoxy resin system, DGEBF and 44DDS, where the relative reaction rates, k2/k1, of epoxy-primary amine, and epoxy-secondary amine reactions are systematically varied to investigate the effect of competitive primary and secondary amine reactivity on the development of network structure and properties. [Display omitted] •Inclusion of kinetics based bonding in simulations of thermosets leads to differences in network formation and properties.•The degree of branching observed in thermoset networks has a direct impact on the materials glass transition temperature.•Using properties predicted via MD simulations, a Time-Temperature-Transformation cure diagram can be constructed.