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Glass transition investigations on highly crosslinked epoxy resins by molecular dynamics simulations

Molecular dynamics simulations at the atomistic level were performed to investigate the glass transition of a highly crosslinked thermoset epoxy resin system composed of diglycidyl ether bisphenol A and isophorone diamine. The crosslinked model was first constructed using a cyclic dynamic method, and extended by investigating the effect of conversion degree on the static properties of local structure, internal energy and volume shrinkage. Based on this model, a systematic investigation on volume, energy and dynamic properties against temperature was made, which determined the glass transition temperature (Tg). The Tgs obtained from various volumetric and energy properties agree well with the differential scanning calorimetry experimental data available, yet a dynamic Tg obtained from the diffusion coefficient is relatively higher. Moreover, the investigation on epoxy segmental dynamics confirmed that the glass transition of the highly crosslinked epoxy resin has a strong dependence on the backbone bond torsional kinetics.