Synthesis and application of a triazine derivative containing boron as flame retardant in epoxy resins

A halogen-free, organic boron/nitrogen compound, 2,4,6-tris-(4-boronphenoxy)-(1,3,5)-triazine (TNB), was synthesized. The thermal and flame-retardant properties of epoxy resins (EP) containing TNB were investigated based on TGA, limiting oxygen index (LOI), vertical burning (UL 94) and cone calorimeter tests. The results showed that the residual char of EP increased after TNB was present. The LOI value of EP/20%TNB reached 31.2% and UL 94 V-0 rating was achieved. The peak heat release rate and total heat release of EP/20%TNB reduced to 305.3 kW/m2 and 58.0 MJ/m2, respectively. In addition, the flame-retarding mechanism was investigated using X-ray diffraction, scanning electron microscopy, laser Raman spectroscopy, elemental analysis, and thermogravimetric analysis-infrared spectroscopy. The results show that TNB is an efficient flame retardant, which is effective in the gas and condensed phases simultaneously.