Studies on fire resistance mechanism of intumescent flame retarded epoxy coating containing zinc borate as a synergistic agent

In order to investigate the synergistic effect and fire resistance mechanism of Trimer combined with Zinc borate (ZB), the intumescent flame retarded epoxy coating was prepared using tri(2, 6, 7-trioxa-1-phospha-bicyclo[2.2.2] octane-1-oxo-4-methanol) phosphate (Trimer) as flame retardant and ZB as synergistic agent. The tests of fire resistance and cone calorimeter demonstrated that appropriate amount of ZB could exert a good synergistic effect. The fire resistant time increased from 17 min to 30 min, the peak-heat release rate decreased from 379.8 kW/m² to 258.5 kW/m², and the peak-smoke release rate reduced from 0.11 m²/s to 0.05 m²/s. The results of thermogravimetric analysis (TGA), Fourier transform infrared spectra (FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) show that the good fire resistance is related to the increase of the residual char, the formation of thermal stable BPO₄ within the residual char and the improvement on uniformity and compactness of the intumescent foamed char.