Ammonium Salts as Curing Agents to Obtain Ionic Epoxy Resins With a Thermoplastic-to-Thermoset Transition.

Abstract

A new class of epoxy thermosets is presented, prepared using ammonium salts as hardeners, enabling the direct formulation of networks with ionic functionality from simple, industrially available building blocks. The curing process occurs in two distinct thermal stages: the formation of a fusible thermoplastic-like intermediate, followed by crosslinking into an infusible thermoset. This intermediate behavior is highly unusual in epoxy systems and allows the material to be processed using methods typically applied to thermoplastics, such as extrusion. The practical relevance of this system is demonstrated through the fabrication of enduring prepregs that can be shaped and handled as thermoplastics during processing, but form crosslinked thermosets upon curing. Finally, the cured matrix can be chemically solubilized in aqueous nitric acid under relatively mild conditions, allowing efficient recycling of intact carbon fibers. This work introduces a scalable platform for functional epoxy networks with broad processing and application potential.