The curing behavior of the epoxy/dicyandiamide (DICY)/2-methylimidazole system with intercalated clays

Abstract

The curing behavior of the epoxy/dicyandiamide/2-methylimidazole system in the presence of montmorillonite clays intercalated with different compounds are analyzed by Fourier transform infrared spectroscopy (FTIR) and with differential scanning calorimetry (DSC). The properties of intercalated clays were analyzed by X-ray diffraction and thermal gravimetric analysis (TGA) and it was obtained that the d-spacing of different intercalated clays follows the order of the siloxane-clay>org-clay>epoxy resin-clay>pristine clay; this trend is consistent with the amount of intercalated chemicals obtained from TGA. The results of FTIR and DSC indicate that the curing exotherms, curing rates, formed functional groups, and curing mechanisms (reaction order) of the epoxy resin system are affected by the curing temperature and the type of intercalated clay used because of the stoichiometric imbalance of reactive groups resulted from the mutual diffusion of epoxy resin constituents and intercalated chemicals. The curing heats of the epoxy resins with different clays are in the order of the epoxy resin-clay> siloxane-clay>org-clay. It is shown that the Kamal model when applied can correctly describe the curing kinetics of the studied epoxy resin/clay systems at 160 and 170°C.