Preparation and Characterization of Transparent Polycarbonate with High Flame Retardancy and Smoke Suppression

There are great demands for transparent flame-retardant PC in a wide range of applications. Herein, a kind of flame retardant containing sulfonate and phosphazene moieties (HSPP) were synthesized and applied into PC to improve the flame retardancy properties without sacrificing transparency. The results showed that a small amount of HSPP could endow PC with excellent flame retardancy properties. Compared with PC, an improvement with 30.4% in LOI, V-0 rating in UL-94, 25% reduction for THR, and 45% reduction for COY in the cone calorimetry test were achieved when the loading of HSPP in the PC matrix was as low as 0.04 wt %. According to the char morphology and structure analysis, the flame retardancy mechanism was attributed to the synergistic carbonization of sulfonates and phosphazene moieties from HSPP and the enhanced barrier effect of the PC residual char layer with high graphitization and integrity quality. Moreover, the transparency of the PC composite was almost the same as that of pure PC and the mechanical strength and stiffness were also well maintained due to the low-loading of HSPP in PC.