Study on the Performance and Mechanism of Sulfonate Phosphazene High-Efficiency Flame Retardant Polycarbonate

To develop a new type of efficient flame retardant that can both improve the flame retardancy and maintain the mechanical properties of polycarbonate (PC), a novel sulfonated phosphonitrile flame retardant, hexaphenoxycyclotriphosphazene (HPCTP)-SK, was synthesized via an electrophilic substitution reaction using HPCTP and fuming sulfuric acid as raw materials. HPCTP-SK was subsequently introduced into PC. Compared with pure PC, the addition of HPCTP-SK at 0.10 wt% in PC increased the limiting oxygen index value from 26.8% to 35.5%, the UL-94 test passed the V-0 rating, the peak heat release rate was reduced by 44.6%, and the carbon monoxide release (COY) was reduced by 19.4%. Furthermore, the introduction of HPCTP-SK did not show a significant effect on the mechanical properties of PC; the tensile strength of the PC/HPCTP-SK composites remained similar, and the impact strength and flexural strength were only decreased by 2.57% and 12.68%, respectively. The introduction of this advanced flame retardant promotes the high flame retardancy of PC through the synergistic effect of the three elements N, P, and S, which in turn meets the demand for highly efficient flame retardant PC in various industries.