Effect of chemical structure on thermo-mechanical properties of epoxy polymers: Comparison of accelerated ReaxFF simulations and experiments

Chemical structure governs the bulk material properties of thermoset polymers at the macro-scale. In this study, three different amine curing agents — aromatic, cyclo-aliphatic and aliphatic — are reacted with bisphenol-A epoxide using a recently developed accelerated ReaxFF simulation approach for kinetically slow reactions. Accelerated ReaxFF simulations provide reactants with energy (comparable to the barrier energy) to form a stable transition state that, depending upon the proximity and the path of approach, leads to successful cross-linking. While cyclic curing agents result in simulated polymers with local heterogeneities in the molecular structure that can be resolved by annealing, strain rate dependence is manifested prominently in polymers with aliphatic curing agents and less prominent in polymer with aromatic curing agent. Based on the good correlation obtained between simulations and experiments, this work demonstrates that accelerated cross-linking and virtual testing of the polymer can capture the translation of variable chemical structure to thermo-mechanical properties of thermosets.