Flame Retardancy and Mechanical Properties of Bio-Based Furan Epoxy Resins with High Crosslink Density

This work outlines an interesting approach to bioepoxy resins from sustainable 2,5-bis((oxiran-2-ylmethoxy)methyl)furan (BOF). The 3,3′-diamino diphenyl-sulfone (33DDS) and 4,4′-diamino diphenyl-sulfone (44DDS) are employed as hardeners. For comparison, petro-based networks from diglycidyl ether of bisphenol A (DGEBA) are developed as well. The systematic analyses suggest that the BOF/DDS networks show higher crosslink densities and mechanical properties than DGEBA/DDS thermosets. Remarkably, an attractive multilayer tubular microstructure is fabricated in the BOF/44DDS thermosets, and it greatly enhances the mechanical performance. Apart from that, BOF/DDS composites exhibit excellent flame retardancy. Especially, for BOF/44DDS, the self-extinguishment happens in 7 s. The fire retardant mechanism confirms that a low heat release rate and heat release capacity as well as a compact char layer occur in the pyrolysis of BOF/DDS. Thus, the BOF/DDS exhibits superior performance over its DGEBA counterparts and meets a wide variety of requirements in engineering.