Red phosphorus acts as second acid source to form a novel intumescent-contractive flame-retardant system on ABS

A novel halogen-free flame retardant prepared by poly(p-ethylene terephthalamide) and ammonium polyphosphate (APP) on acrylonitrile–butadiene–styrene (ABS) resin has a good flame retardancy when loading is 30 %; but, once the mass fraction is <30 %, the system does not maintain outstanding flame retardancy. To improve the efficiency of this kind of flame retardant and LOI values, higher thermal stability acid source-red phosphorus is introduced. It is found that a little quantity of red phosphorus will improve the flame retardancy of ABS remarkably and will change the process of charring; when the mass fractions of APP, PPTA, and red phosphorus are only 15, 5, and 2 %, respectively, though the LOI of flame-retardant ABS is 27, UL-94 vertical burning test still reach V-0. Thermogravimetric analysis data show that red phosphorus changes the thermal degradation behavior of IFR-ABS system, shrink digital photo display system, and yield more stable residue at higher temperature; Fourier transform infrared results and scanning electron microscopic micrographs show that red phosphorus can catalyze the charring and form much denser char to improve the flame-retardant performance of the materials.