Development of Sustainable Thermosets from Cardanol-based Epoxy Prepolymer and Ionic Liquids

In this work, the development of new biobased epoxy networks using phosphonium-based ionic liquids combined with dicyanamide and phosphinate counteranions as initiators of epoxy prepolymers was compared with a biobased epoxy–amine system. Ionic liquids (ILs) displayed high reactivity toward cardanol-based epoxy prepolymers, and the obtained biobased epoxy/IL networks highlighted a glass transition temperature of around 30 °C, an excellent thermal stability higher than 450 °C and higher hydrophobic behavior compared to biobased epoxy–amine networks. In addition, the use of a cardanol-based epoxy prepolymer as a modifier of epoxy/IL networks was also investigated. In this case, the final properties of epoxy/IL networks were improved by the presence of biobased epoxy compounds, especially their surface energy as well as their fracture toughness (+180%), suggesting a new way to develop partially biobased epoxy coatings.