Effect of char-forming agents rich in tertiary carbon on flame retardant properties of polypropylene

In this research, a novel type of triazine-based char-forming agent (PTPA) was synthesized and combined with ammonium polyphosphate (APP) to form an intumescent flame retardant (IFR) system to prevent polypropylene (PP) burning. A commercialized char-forming agent was purchased and the same process was used to study its flame retardant performance on polypropylene, and the results were compared with those of this experiment. It was found that the PP/IFR samples in this experiment (APP/PTPA = 4/1–1/1) reached the increased limiting oxygen index (LOI) value of 29.5%, and passed the vertical combustion (UL-94) V-0 rating. The maximum LOI for the purchase of char-forming agent is 31.0%. Thermogravimetric analysis results show that the PTPA/APP system can improve the thermal stability and thermal oxidation stability of carbon slag. The carbon residue was further studied by visual observation and scanning electron microscopy. The dense coke residues formed hinder the transfer of gas and heat during the combustion process, and ultimately endow the PP/IFR system with higher flame retardancy.