Rheological and thermal study of the curing process of a cycloaliphatic epoxy resin: application to the optimization of the ultimate thermomechanical and electrical properties

The curing process of a cycloaliphatic epoxy resin was defined using different experimental techniques to obtain a material with optimal mechanical and electrical behaviour and with the ultimate objective of its application in the production of polymer-based insulator for railway transportation. The temperature domain characteristic of the crosslinking was determined by differential scanning calorimetry. However, thermogravimetric analyses of the reactive species supported that a low curing temperature had to be chosen during the initial crosslinking stage. Then, kinetic viscoelastic experiments were performed to identify the time and temperature conditions necessary to observe the gelation and vitrification of the reactive mixture. To fulfil higher requirements of productivity and performances, a two-step thermal cycle was defined and optimized by investigating the influence of different curing schedules on the glass transition temperature of the crosslinked material. The effects of the curing profile on the dielectric strength of the material were also investigated. Good correlations between the different techniques were observed and explained in terms of structure–property relationships.