TGA-FTIR and char residue analysis: studying the synergistic flame retardancy mechanism of ionic liquid-modified graphene and hexaphenoxy cyclotriphosphazene

The thermal degradation and flame retardancy effect between ionic liquid-modified graphene and hexaphenoxy cyclotriphosphazene on epoxy resin (EP) was investigated using thermogravimetric analysis, differential thermogravimetric analysis, thermogravimetric analysis-infrared spectrometry (TGA-FTIR) and the char residue analysis. The carbonization and synergistic flame-retardant mechanism were obtained. The results showed that, compared with pure EP, the char residue amount of flame-retardant EP was increased, which was dense and continuous with fewer and smaller pores. This was due to the compatibilization of the ionic liquid to the matrix, resulting in the good dispersion of the flame retardant in EP matrix to promote the carbonization efficiency. The TGA-FTIR analysis showed that the PO·and HF free radicals produced by decomposition of flame retardants quenched the flame in the gas phase, and the produced water vapor and NH3 diluted the concentrations of combustible gas and oxygen to inhibit the progress of combustion.Graphical abstract