A novel synergistic phosphorus-nitrogen flame retardant for epoxy compositions and flame-retardant coatings

The interaction of hexa methoxymethyl melamine with ammonium dihydrogen phosphate at 100oC was investigated. It is shown that under the action of an adduct of ammonium dihydrogen phosphate and hexa methoxymethyl melamine, homo condensation of the latter occurs and encapsulation of the unreacted part of ammonium dihydrogen phosphate occurs. The maximum polymer yield output corresponds to the threshold at the atomic ratio N:P=1:1 in the combined product. Encapsulated complex nitrogen-phosphorus-containing flame retardants were synthesized, which are used to determine fire resistance of epoxy resin cured with polyethylene polyamine. The optimal composition of complex flame retardants (atomic ratio close to 1:1) were found, which provides the fire resistance of the composite material V0 (UL 94 test) and the oxygen index of 32-36% with a 20% mass fraction of flame retardants in the composite material. The formation of protecting char on the surface of the substrate in the flame of a gas burner allows the composite material to be used as a flame-retardant coating for different constructions.