Effect of homemade PON compounded with expanded graphite ratio on flame retardancy of polystyrene resin

Abstract In this paper, diphenyl phosphoryl chloride and anhydrous piperazine are used as raw materials to prepare a kind of homemade flame retardant (PON) with P‐N synergistic effect by nucleophilic substitution reaction. The properties of polystyrene/PON/ expandable graphite composites are analyzed by limiting oxygen index (LOI), thermogravimetric analysis (TGA), cone calorimetry (CONE) and scanning electron microscopy (SEM). The effects of different ratios of PON and expandable graphite (EG) on the flame retardant properties of polystyrene resin are investigated. The results show that when the total amount of flame retardant is 10 wt%, the ratio of PON and EG is 3:2 and 1:1, which is better than the other ratios. However, due to the small amount of flame retardant, the optimal synergistic effect of PON and EG is not obvious, and the flame retardant performance is similar. However, when the total amount of flame retardant increases to 20 wt%, it is obvious that the ratio of PON and EG 3:2 is better than 1:1.