Abstract: A mixture of nickel ion-containing metal organic frameworks （Ni-MOF） and piperazine pyrophosphate （PPAP） was incorporated into epoxy resin （EP） to form compounding EP thermosets， and their flame-retardant performance and smoke release behaviors were investigated by means of limiting oxygen index （LOI）， vertical burning test， and cone calorimeter （CONE）. The results indicated that the compounding EP thermosets achieved a UL 94 V-0 classification in the vertical burning test， and their LOIs reached 27.9 vol% with the addition of 6 % PPAP. However， the EP/PPAP/Ni-MOF compounding thermosets obtained a UL 94 V-0 classification together with a LOI of 29.3 vol% with the addition of 5 wt% PAPP/Ni-MOF at a mass ratio of 99∶1. These results demonstrated that the addition of a small amount of Ni-MOF effectively improved the flame retardancy for EP thermosets. Cone calorimetric test results indicated that the EP/PPAP/Ni-MOF compounding thermosets exhibited an obviously lower heat release rate， total heat release， smoke release rate and total smoke release than the EP/PPAP ones under the same loading of flame retardants. The addition of Ni-MOF inhibited the combustion intensity and smoke release of EP thermosets. Nickel ions in Ni-MOF could be cross-linked with the phosphoric acid and polyphosphoric acid generated from the thermal degradation of PPAP， which resulted in more phosphorus components remaining in the condensed phase. Consequently， sufficient char layers with good strength were formed to effectively inhibit the release of heat and smoke during combustion. This enhanced the fire safety performance of EP thermosets significantly.

Key words: epoxy resin, flame retardant, smoke suppression, nickel-containing metal organic framework material, piperazine pyrophosphate