DSC and FTIR analyses of the curing behavior of epoxy/DICY/solvent systemson hermetic specimens

The curing characteristics of a dicyandiamide-cured epoxy system under the influence of solvents in a closed environment were studied by means of isot hermal differential scanning calorimetry (DSC) and Fourier transform infrar ed spectroscopy (FTIR). The DSC analyses revealed that the presence of solv ent results in decreases in the curing exotherm, the initial curing rate, t he glass transition temperature, the reaction rate and the reaction order o f the epoxy resin. The greatest decreases were caused by the solvent with t he highest boiling temperature. A change in temperature-dependent curing ro ute due to the heat absorbed during solvent evaporation is responsible for the difference. The FTIR analyses confirmed that the composition of the cur ed resin is affected by the solvent, the curing temperature and the specime n configuration. As compared with those obtained from open systems, specime ns produced in a closed environment have an enhanced curing exotherm, initi al curing rate, glass transition temperature, reaction rate and reaction or der because of the retention of volatile catalytic by-products.