The effect of epoxy resin and curing agent groups on mechanical properties investigated by molecular dynamics

Epoxy resin is an excellent material known for its low density, high stability, and strong chemical resistance. However, its further development has been hindered by the inadequate mechanical properties of its matrix and the lack of research into the mechanisms by which various groups within its crosslinking network affect these properties. Reactive force field (ReaxFF) was adopted to calculate the epoxy resins formed by AFG-90MH and AFG-90 H with curing agents MOEA, MOCA, DDM, and MCDEA. The influence of groups and structures within the crosslinking network on the mechanical properties and glass transition temperature (Tg) of the systems was studied by employing a controlled variable approach. The results indicate that the epoxy resin crosslinking network (AFG-90 H) with uniformly distributed epoxy side chains exhibits a denser structure, but it possesses weaker mechanical properties and a lower Tg. However, the situation with AFG-90MH is the opposite. The presence of Cl on the curing agent has been found to increase the Tg of the cross-linked system, whereas the ethyl groups tend to decrease the Tg. Furthermore, the chlorine element on the curing agent leads to a reduction in the mechanical properties of the epoxy resin system. In dense systems, the presence of ethyl groups strengthens the mechanical properties of the epoxy resin, but in dispersed systems, the influence is adverse.