Intrinsically flame retardant bio-based epoxy thermosets: A review

At present most of epoxy thermosets is dependent on petroleum-based resources especially diglycidyl ether bisphenol A (DGEBA)-type epoxy monomers produced from epichlorohydrin (ECH) and bisphenol A (BPA). Owing to the limitation of the greenhouse gas emission, development of the bio-based epoxy thermosets is gaining increasing attention to substitute the petroleum-based ones. However, the bio-based epoxy thermosets possess similar high flammability to their petroleum-based counterparts. It is thereby necessary to endow them with flame retardancy. This review article aims to summarize the most relevant and up-to-date advances in intrinsically flame retardant bio-based epoxy thermosets. First, the approaches to synthesis of bio-based intrinsically flame retardant epoxy monomers are introduced briefly. Subsequently, the review focuses in particular on partly bio-based intrinsically flame retardant epoxy thermosets from either bio-based epoxy monomers or bio-based curing agents in terms of their flame retardant property as well as mechanical property and thermal stability. Additionally, the fully bio-based intrinsically flame retardant epoxy thermosets are also reviewed. Finally, we will provide a brief comment on opportunities and challenges for future growth of bio-based intrinsically flame retardant epoxy thermosets.