Synergistic flame retardancy of solid acid, hindered N-alkoxy amine, and halogen compound for polypropylene

Polypropylene (PP) is a thermoplastic resin widely used in various industrial applications. However, the flammability of PP is a severe drawback that lowers operational safety. This study demonstrates the development of flame-retardant PP. The co-adding with various solid acids and a hindered N-alkoxy amine (NOR116 - Flamestab((R)) NOR 116 FF) affects the combustion behavior of PP in a vertical flame test. The co-adding of silica alumina (SA) and NOR116 with PP promoted the melt drip, suppressed upward combustion heat, and shorter the combustion time. The decomposition products of NOR116 induced the cleavage of the main chain of PP, and it quenched the radicals on the surface of the SA particles because SA has abundant acidic sites and large pores, facilitating the adsorption of a substantial quantity of NOR116. The molecular weight of PP was controlled to 10(3) similar to 10(4) before the combustion to achieve an increase in the melt flow ability and suppress the upward combustion. Furthermore, a small amount of a halogen-based flame retardant was incorporated into the PP/SA/NOR116 sample, and the specimens could instantly self-extinguish on the gas phase by radical trap.