Synthesis of bio-based fire-resistant epoxy without addition of flame retardant elements

Blending with flame retardants or introducing fire resistant elements into their skeletons is a routine method to obtain the fire resistant epoxy resins. Herein, we report a novel epoxy monomer diglycidyl ether of genistein (DGEG) synthesized from the renewable genistein, and after it was cured with 4, 4-diaminodiphenylmethane (DDM), the intrinsically flame-retardant resin (DGEG/DDM), which contains only C, H and O elements, was obtained. The DGEG/DDM system demonstrates a total heat release (THR) as low as 6.3 kJ/g measured by microscale combustion calorimetry (MCC), a high limiting oxygen index (LOI) of 33.1%, and the flammability rating of V-0 in UL94 test. In addition, when compared with the bisphenol A epoxy resin system (DER332/DDM) cured under the same condition, DGEG/DDM exhibits higher glass transition temperature (223 degrees C vs. 175 degrees C) and shows a 12%, 19%, 33% and 183% increment in storage modulus (25 degrees C), tensile strength, flexural strength and residual char value at 800 degrees C, respectively. The results in this work provide us a new strategy to synthesize high performance flame retardant epoxy resins by taking advantages of the unique structures of renewable compounds.