Functionalized allylamine polyphosphate as a novel multifunctional highly efficient fire retardant for polypropylene

In this study, an efficient novel allylamine polyphosphate (AAPP) as a flame retardant (FR) crosslinker is used to improve the thermal stability of flame retarded polypropylene (PP) composites under electron beam treatment. First, a multifunctional AAPP has been designed and synthesized via a simple ion exchange reaction of the common ammonium polyphosphate (APP). AAPP was mixed with PP via a twin-screw extruder to prepare a series of flame retarded PP composites. Afterwards these composites were irradiated with high energy electrons in order to increase their thermal stability. The results showed an increased LOI value of PP/AAPP composites and effective melt dripping resistance in the UL-94 test in comparison with traditional PP/ammonium polyphosphate (APP) composites. Moreover, CC data like the heat release rate (HRR), total heat release (THR), smoke production rate (SPR), and total smoke production (TSP) showed that AAPP had a much better contribution to the flame retardation of PP than APP. Besides, AAPP provided an excellent quality of char residue in the combustion stage due to its P–N–C and P–O–C structures. Moreover, the environment-friendly electron beam technology was an efficient approach to improve the thermal stability of these multifunctional flame retarded PP composites without the use of additional stabilizers. This innovative idea may be expanded to other polymer systems to develop high performance polymer composites by environment-friendly electron beam technology.