Determination of the formulation and curing conditions of thermosetting epoxy resins for optimizing their properties and future use in gelcasting process

Abstract This work investigates the suitability of epoxy resins for possible use in an industrial gelcasting process. Two different formulations are studied using complementary experimental techniques. Both reactive formulations are based on a difunctional epoxy prepolymer (aliphatic BDGE or aromatic RDGE) mixed with a polyamine hardener (TEPA). The combination of analytical chemistry (NMR and FTIR spectroscopy) and calorimetric measurements (DSC) are used to determine the optimal epoxy/amine ratio for each reactive formulation. The gelation and vitrification times are investigated by dynamic rheometry through kinetic analyses over a large range of fixed temperature. It is found that the RDGE‐TEPA mixture is more reactive than BDGE‐TEPA with shorter curing starting times. The thermomechanical analyses performed on both optimized formulations show that the RDGE‐TEPA material presents better performances after curing ( T g close to 80°C) than the BDGE‐TEPA system ( T g lower than ambient temperature). Then, the effects of the cooling cycle on the thermomechanical profile of each polymer are investigated. The RDGE‐TEPA formulation is found to be much more subject to the formation of internal stresses created during the cross‐linking and cooling step than the BDGE‐TEPA material. Considering all these criteria, the BDGE‐TEPA system is ultimately more suitable for the gelcasting process than RDGE‐TEPA.