Effect of a novel phosphorous–nitrogen containing intumescent flame retardant on the fire retardancy and the thermal behaviour of poly(butylene terephthalate)

Abstract

A novel phosphorus–nitrogen containing intumescent flame retardant (P–N IFR) was prepared via the reaction of a caged bicyclic phosphorus (PEPA) compound and 4,4′-diamino diphenyl methane (DDM) in two steps. The product was added to poly(butylene terephthalate) (PBT) to obtain halogen-free flame retarded polyester. UL-94 test, thermogravimetry and in situ infrared spectroscopy were used to characterize the flammability, thermal degradation properties and the char-forming process. It was shown that the phosphorus–nitrogen containing compound could improve both the flame retardancy and thermal stability more effectively than other P–N flame retardants. Furthermore, it was a good char-forming agent incorporated with the co-addition of polyurethane (PU) when the combustion occurred. The formation of P–N structure was incorporated in the char layer.