Bio-epoxy resins with inherent flame retardancy

Nowadays, roughly 90% of worldwide epoxy resin materials are made from diglycidyl ether of bisphenol A (DGEBA). This resin offers unique features such as outstanding mechanical properties, chemical resistance, and shape stability. By contrast, the growing awareness of environmental issues, global warming, and depletion of petroleum reservoir suggest search for using bio-epoxy resin from sustainable resources. Indeed, DGEBA is a petroleum-based monomer obtained from bisphenol A and epichlorohydrin, two potential precursors harmful for the environment and human health as well. The problem deepens when it comes to the high flammability of such materials, which restricts their use in strategic applications. Although the introduction of flame retardant (FR) additives to epoxy matrices has been a major strategy to induce flame retardancy, negative impact on mechanical properties and migration of FRs to the materials' surface remained unresolved issues. Tailoring epoxy chains with chemically bonded reactive flame retardants to epoxy resins would be the solution to avoid migration of FRs to surface, along with protecting mechanical properties of resin. With the rapid development of reactive bio-based FRs and epoxy resins, production of flame retardant bio-epoxy with high biomass content has become a promising strategy to address these issues. This conside review encompasses latest progress in flame retardant bio-epoxy resins made of different resources, with inherent chemical structures of either epoxy monomers or embedded reactive flame retardant elements.