Intrinsically Anti-Flammable Apigenin-derived Epoxy Thermosets with High Glass Transition Temperature and Mechanical Strength

In this work,apigenin was chosen as a raw material to synthesize a novel epoxy monomer(DGEA),while the bio-based epoxy resin was further obtained after curing with 4,4’-diaminodiphenylmethane(DDM).The control samples were prepared by curing diglycidyl ether of bisphenol A(DGEBA)with DDM.The non-isothermal differential scanning calorimeter(DSC)method was utilized to further investigate the curing behavior and curing kinetics of the DGEA/DDM system.Despite no flame retardant active elements,the DGEA/DDM thermoset still exhibited exceptional anti-flammability.Specifically,the DGEA/DDM thermoset reached a V-0 rating in the UL-94 test and owned a high limiting oxygen index(LOI)value of 37.0%,while DGEBA/DDM resins were consumed completely in the vertical combustion test with a low LOI of 23.0%.Furthermore,the microscale combustion calorimetry(MCC)results manifested that compared with DGEBA/DDM resins,both PHRR and THR values of the DGEA/DDM resins were dropped by 84.0%and 57.6%,respectively.Additionally,the DGEA/DDM resin also presented higher storage modulus and tensile strength compared with DGEBA/DDM one.Particularly,in contrast with that of the cured DGEBA/DDM one(156℃),the DGEA/DDM thermoset displayed an extremely high glass transition temperature(232℃).This study breaks new ground on how to produce biobased monomers with aromatic structures and achieve high-performance thermosetting polymers.