Synthesis of phosphazene‐triazine bi‐base sulfonate and its applications in flame‐retardant modified polycarbonate

Abstract A phosphazene‐triazine bi‐base sulfonate compound (CPNS) was synthesized using hexachlorocyclotriphosphazene, cyanuric chloride, and sodium p‐hydroxybenzene sulfonate as raw materials. The chemical structure was determined by FTIR, 1 H NMR 31 P NMR (NMR stands for nuclear magnetic resonance), and elemental analysis of P, Na. To study the flame retardant properties of CPNS, a series of modified polycarbonate (MPC) with different ratios of CPNS were prepared. The flame retardant performance and thermal stability of CPNS/MPC were characterized by limiting oxygen index (LOI), UL‐94 vertical burning test, cone calorimetry test, and TG. Results show that when CPNS is added to 0.3%, the CPNS/MPC can pass the UL94 V‐0 level with an LOI value of 35.3% and reduce the peak heat release rate by 16.89% during the combustion. TG results show that adding 0.1% CPNS can decrease the initial decomposition temperature of the MPC by 68°C in nitrogen and 27°C in air. The reduction of the initial decomposition temperature means that the flame retardant promotes the isomerization reaction of polycarbonate accelerates the formation of an intermediate char on the surface. Investigation of intermediate char residue's morphology and chemical structure demonstrates that CPNS promotes the formation of more complete and compact char residue, which acts not only there is increased opportunity for radical recombination reactions in the condensed phase but also as physical barriers to inhibit the transfer of heat and oxygen, resulting in good flame retardant properties.