Nickel hydroxide and zinc hydroxystannate dual modified graphite carbon nitride for the flame retardancy and smoke suppression of epoxy resin

•A functionalized carbon nitride (g-C3N4/Ni(OH)2/ZHS) nano-hybrid containing Ni, zn and sn was synthesized.•g-C3N4/Ni(OH)2/ZHS nano-hybrid can significantly reduce the heat, smoke and CO yield of EP.•The possible flame retardant mechanism of g-C3N4/Ni(OH)2/ZHS was investigated. A functionalized graphite carbon nitride (g-C3N4) nanosheet was prepared by coprecipitation method. and its effect on the thermal stability, flame retardancy and mechanical properties of epoxy resin (EP) was investigated. Thermogravimetric analysis (TGA) results showed that the char residue of EP g-C3N4/β-Ni(OH)2/ZHS composite increased significantly. The result of the hybrids on the fire hazard of EP showed that the combination of g-C3N4, β-Ni(OH)2 and zinc hydroxystannate (ZHS) was more advantageous than a single nano-component in reducing the fire hazard of EP. The peak heat release rate, total heat release, smoke production rate and total smoke production values of the EP/g-C3N4/β-Ni(OH)2/ZHS composite were reduced to 761.9 kW/m2, 86.9 MJ/m2, 0.31 m2/s and 32 m2 which were 39.2%, 15.5%, 39.2% and 14.2% lower than those of EP, respectively. The addition of ternary hybrid reduced the mechanical properties, but it was improved compared with the use alone. Furthermore, based on the analysis of the char residue of the condensed phase, the possible flame retardant mechanism was proposed.