The curing and thermal transition behavior of epoxy resin: a molecular simulation and experimental study

Curing and thermal transition behavior of two epoxy resins i.e. 2,2'-dimethyl-4,4'-diaminobiphenyl (MTB)-4,5-epoxycyclohexyl-1,2-diglycidyl diformate (TDE85) and 2,2'-bis(trifluoromethyl)-4,4'-diamino biphenyl (TFMB)-4,5-epoxycyclohexyl-1,2-diglycidyl diformate (TDE85) with different chemical structures were experimentally and theoretically investigated via molecular simulations to establish the structure-property relationships. The slight modification in the diamine structure resulted in significant changes in the curing and glass transition behavior of epoxy resin. As the side group of the diamine was changed from methyl to trifluoromethyl, the reactivity of the diamine toward epoxy decreased and the glass transition temperature increased from about 164 degrees C to about 191 degrees C. These phenomena can be illustrated by the change of the reaction energy barrier, flexibility of chains and the cohesive energy density in the molecular simulation of the curing process. The simulated values show good agreement with experimental data, and can be used to predict the related material characteristics for the different amine curing agent-epoxy systems.