Prediction of the glass transition temperature of cycloaliphatic amine–epoxy networks

Stoichiometric, completely cured binary or ternary mixtures of the diglycidylether of bisphenol A (DGEBA), isophorone diamine (IPD), and trimethylcyclohexylamine (TMCA) monomers were studied by differential scanning calorimetry. The relations between the glass transition temperature T_g and the structure of the copolymer networks were investigated. Good predictions of T_g can be obtained on the basis of the following hypothesis: (1) the molar contributions M_iT^?1_gi to the “copolymer effect” of difunctional groups are additive, (2) the crosslinking effect can be expressed by the DiMarzio relation in which the molar contribution of crosslink mers is an increasing function of the stiffness of linear segments. For the seven systems under study, the deviation between calculated and experimental T_g values is within experimental scatter.