Synthesis of an organophosphorus flame retardant derived from daidzein and its application in epoxy resin

For the concern of sustainable and green chemical engineering , the development of flame retardants from renewable biomaterials is particularly attractive. Daidzein is an isoflavone found in large amounts in soybeans and other legumes. The structure of daidzein permits easy reaction with flame retardant groups and is beneficial for the formation of char at high temperature. A flame retardant which can work in both the gas phase and the condensed phase may be unusually effective. An organophosphorus flame retardant (DPOD) has been prepared using daidzein and diphenylphosphinyl chloride, and used to modify the flammability of epoxy (EP) resin. The structure and flame retardant mode of action of DPOD in EP were explored. The results showed that DPOD works in both the gas phase and the condensed phase and improves the flame retardancy of EP blends greatly. In addition, the DPOD doesn't deteriorate the glass transition temperature and impact strength of EP blends. This work is a useful attempt to use biobased monomers in the design of flame retardants.