Hard epoxy thermosets obtained via two sequential epoxy-amine condensations

A new family of dual-curable poly(β-hydroxyamine ether) thermosets based on amine-epoxy formulations has been prepared and characterized. Both curing stages consist in an epoxy-amine polycondensation, each having different reactivity. Whereas the first one is carried out at relatively low temperature using an aliphatic flexible amine, the second is carried out at high temperature with a rigid aromatic amine. The sequentiality of the curing and the stability of the intermediate materials can be established in the basis of the different nucleophilicity of the amines used. The aromatic amine, with a weakly nucleophilic character, is not able to react with epoxides during the first stage at low temperature. The intermediate and final materials exhibit a wide range of properties, thanks to the different glass transition of both epoxy-amine networks, and can be tuned by changing the relative proportion of both diamines in the formulation. The participation of the epoxy resin in both curing stages ensures the homogeneity of the prepared materials, rendering them excellent candidates for applications such as adhesives or smart materials.