A novel highly efficient intumescent flame-retardant polypropylene: Thermal degradation, flame retardance and mechanism

The flammability of polypropylene (PP) brings great fire hazards, so it is of great significance to enhance its flame retardancy. In this paper, a high-efficiency intumescent flame retardant (IFR), composed of ammonium polyphosphate (APP) and poly(piperazine phenylphosphamide) charring agent (BPOPA), was prepared and used to improve the flame retardancy of PP. With the 25 wt% of APP/BPOPA (3:1) addition, the limiting oxygen index of PP composite reached 32%, which could pass a UL-94 V-0 rating. Besides, the peak of heat release rate (PHRR) and total smoke product (TSP) of PP with 25 wt% IFR were declined by 71.8% and 68.9% respectively compared with PP. What’s more, the interaction of APP and BPOPA was also explored and the result showed the combination of APP and BPOPA could form a compact and intumescent char layer to restrain the combustion of PP.