Phosphorus-containing Salen-Ni metal complexes enhancing the flame retardancy and smoke suppression of epoxy resin composites

Two novel Salen-DPCPs metal complexes (Salen-DPCP-1 and Salen-DPCP-2), containing both Salen-Schiff base (Salen), phenyl phosphate structures (DPCP) and nickel component, were prepared to reduce fire hazards of epoxy resin (EP). The results showed that 5 wt % addition of Salen-DPCP-1 brought a higher flame-retardant efficiency to the EP, where the V-0 rating in UL-94 burning test and 31.5% of limiting oxygen index (LOI) were achieved. Meanwhile, total heat release, total smoke production, and total CO yield dramatically decreased by 28.1, 23.6, and 21.4%. In addition, these results basically reappeared when Salen-DPCP-2 were introduced into EP to obtain Salen-DPCP-2/EP composites. Chemical structure and morphology characterization of the carbon residue confirmed that Salen-DPCPs improved the catalytic charring ability and the noncombustible gas releasing ability by the Fourier transform infrared, X-ray photoelectron spectroscopy, and Scanning electron microscopy technology. Therefore, it is an efficient strategy to develop novel Salen composites modified by flame-retardant groups to improve the fire rating of polymers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137 , 48734.