Physical properties of epoxy polymers during curing process

Based on a study of the temperature dependences of the specific heat capacity СР of selected samples of epoxy polymers UP-643 and ED-20 at different stages of the curing process, the change in thermophysical characteristics has been studied. Calculation of the glass transition temperature Tg, the heat release during post-curing ΔH and the degree of conversion αi of epoxy groups made it possible to show the influence of the active modifiers epoxyether (ET) and dibutyl phthalate (DBP) on the rate of the curing reaction. The use of a dynamic calorimeter and a technique for studying selected samples of epoxy polymer at different stages of the curing process made it possible to calculate the change in thermophysical characteristics and evaluate the key stages of this process, such as gelation and glass transition. A study of the post-curing process of an epoxy polymer based on UP-643 resin in a dynamic calorimeter made it possible to show that the glass transition temperature Tg and the amount of heat released during post-curing ΔH more quickly reach equilibrium values ​​at high pre-curing temperatures. The temperature dependences of the heat capacity of an epoxy polymer based on ED-20 resin modified with epoxyether and dibutyl phthalate made it possible to conclude that the glass transition temperature Tg and the amount of heat released during post-curing ΔH and the rate of completion of the reaction reach equilibrium values ​​more likely in the case of unmodified and modified by ET resin than in the case resin modified by DBP. This fact can be explained by the fact that dibutyl phthalate molecules apparently shield the epoxy groups and, thus, inhibit the reaction.