Fabrication of two multifunctional phosphorus–nitrogen flame retardants toward improving the fire safety of epoxy resin

Abstract

Abstract To improve the fire safety of epoxy resin (EP), two novel phosphorus–nitrogen flame retardants, which named as diphenyl allylphosphoramidate (DPCA) and N-allyl-P, P-diphenylphosphinic amide (DCA), were synthesized by acyl chloride reaction and introduced into EP for fabricating EP composites. The combustion tests showed that incorporation of 5 wt% DPCA or 5 wt% DCA into EP led to the exceptional limited oxygen index (LOI) value (27.1% or 31.6%). Besides, the peak of heat release rate of EP-5 wt% DPCA and EP-5 wt% DCA was reduced by 40.69% and 36.69%, respectively, compared to pure EP. The enhanced fire resistance of EP was ascribed to the trapping effect of fillers in the gas phase and the charring effect in the condensed phase. Furthermore, ultraviolet-visible spectra revealed that both EP-5 wt% DPCA and EP-5 wt% DCA have considerable transparency. This study is expected to broaden the application of EP in the industrial area.