Effects of flame retardants containing P-O-C and P-C structures on the flame retardant properties of epoxy resin

So far, discussions on the effects of elements on flame retardant properties have been widespread in flame retardant-related fields, but reports on the effects of specific structures on flame retardant properties are rare. In this work, two novel phosphorus-nitrogen flame retardants were synthesized from diphenylphosphinyl chloride and diphenyl chlorophosphite. It was proved that the P-O-C structure of the DOAT flame retardant is beneficial to form a more stable carbon layer with high phosphorus content and reduce the total amount of smoke, while the P-C structure of DPAT flame retardant is conducive to produce a large amount of phosphorus-containing substances in the gas phase, while the phosphorus content in the residual carbon is very low. Therefore, the DOAT flame retardant mainly plays a flame retardant role in the condensed phase. The DPAT flame retardant mainly plays a flame retardant role in the gas phase. The flame retardant action mechanism of the combustion process was also investigated by using scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and Thermogravimetric analysis/infrared spectrometry (TG-IR).