Impact on flame retardancy and degradation behavior of intumescent flame-retardantEPcomposites by a hyperbranched triazine-based charring agent

The flame retardancy and thermal degradation behavior of intumescent flame retardant EP (EP-IFR) composites based on ammonium polyphosphate (APP) and a hyperbranched triazine carbon forming agent (HTCFA) were investigated by the means of limited oxygen index (LOI), vertical combustion test (UL-94), thermogravimetric analysis (TGA) and cone calorimeter test (CONE). The results exhibited that the combination of APP and HTCFA obviously imparted better flame retardancy to EP than them applied alone. EP composites containing 10 wt% APP/HTCFA (4/1) passed UL-94V-0 rating with a LOI value of 32%, while there was no rating for EP-APP or EP-HTCFA. In addition, the combination of APP and HTCFA influenced the fire behavior of composites with more efficient heat/smoke release suppression. The carbonaceous residues after cone presented expanded structures with compact and continuous surfaces. TGA results presented that there was an obvious synergistic effect between them, significantly enhancing the thermal stability and promoting the formation of char residues. The flame retardant mechanism was also involved based on the residue analysis by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectrometry (FTIR) and laser Raman spectrometer (LRS). Results illustrated high-quality foamed cellular char layers with highly graphitic degree contributed to better flame retardant and smoke suppression properties of EP-APP/HTCFA composite.