AbstractSome physical properties of epoxy resins cured with 2‐substituted imidazoles, e.g., 2‐ethyl‐4‐methylimidazole (EMI‐24), and 1‐substituted imidazoles, e.g., 1‐methylimidazole (MI‐1), were studied in order to determine the effect of additional crosslinking that has been proposed to occur with EMI‐24. While these catalysts were found to yield identical physical properties in that system, they were found to behave differently when the epoxy resin was flexibilized with a polysulfide rubber. Evidence from infrared (IR) and nuclear magnetic resonance (NMR) spectra proved that imidazoles unsubstituted in the 2‐position were being deactivated through their conversion to a dihydroimidazole compound in a proportion related to the amount of polysulfide rubber present. Hence, only imidazoles substituted in the 2‐position will cure epoxy–pol
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