A novel phosphorus compound acting as a substitute of DOPO for flame retard of epoxy resin

9,10-Dihydro-9-oxa-10-phosphaphenanthrene (DOPO) is the star product in flame retard of epoxy resin (EP). However, its limited production capacity can hardly meet the market demand. In this work, a new phosphorus-containing flame retardant named as methanephosphonite (MTA) was successfully synthesized to substitute the DOPO in EP. Due to the supreme efficiency of the gas phase mechanism, only 1.5 wt% of phosphorus is sufficient to achieve V0 rating and the LOI is as high as 31.4%. In addition, MTA can effectively suppress the heat release during combustion, and the peak of the heat release rate (pk-HRR) of the MTA/EP-2.0 decreases 50% than that of neat EP. Besides, the introduction of MTA does not significantly deteriorate the mechanical properties of the thermoset MTA/EP-1.5, both of the flexural strength and impact strength reduce less than 15%, which shows a great value for EP material.