Iron-phosphorus-nitrogen functionalized reduced graphene oxide for epoxy resin with reduced fire hazards and improved impact toughness

Novel iron hexamethylenediaminetetrakis-(methylenephosphonate) (Fe-HDTMP)-reduced graphene oxide (FerGO) hybrids were prepared by in situ immobilization of Fe-HDTMP nanoparticles and the reduction of graphene oxide via a hydrothermal strategy. Fe-rGO modification of epoxy resin (EP) improved mechanical properties, flame retardancy, smoke suppression, and thermal stability by combination with flame retardant elements (i.e. Fe, N, and P) and graphene nanoplatelets. The incorporation of 1% Fe-rGO increased the impact strength and storage modulus of EP by 19.2, and 27.9%, respectively. Additionally, the incorporation of 5% Fe-rGO helped EP/5Fe-rGO achieve UL-94 VO rating with a limiting oxygen index of 30.5%. Compared to untreated EP, the modified EP exhibited 68.2% lower release of total smoke, 54.5% decreased peak CO production rate, 66.3% lower total heat release, and 47.7% reduced peak heat release rate of EP/5Fe-rGO. In addition, the glasstransition temperature of EP/Fe-rGO nanocomposite was maintained at a high level. The improved fire safety performance of EP/2Fe-rGO nanocomposite was due to the catalyzing carbonization effect, the release of inert compounds of Fe-rGO in condensed and gas phases, and the barrier effect of graphene.