Sulfonate-Group-Containing Polymeric Polyamide for Simultaneous Transparency and Flame Retardancy of Polycarbonate

In the functionalization of transparent polycarbonate (PC), the addition of additives often results in damage to the transparency of polycarbonate, thereby limiting its application in the field with a high transparent requirement. In this study, sulfonate-group-containing polymeric polyamide SK was synthesized and employed as a functional agent for PC. The results demonstrated that the SK significantly improved the fire safety of PC. 1.0 wt % SK endowed PC with a UL-94 V-0 rating and a limiting oxygen index of 30.4%; compared with that of neat PC, the maximum smoke density (Dsmax) and the peak of heat release rate (PHRR) for 1.0 wt % SK-blended PC were decreased by 21% and 39%, respectively. More importantly, the transparency of the original PC was maintained at 86.4% after incorporation of 1.0 wt % SK, showing only a slight reduction. Here, excellent flame retardancy is ascribed to the synergistic effect of SK-caused physical cross-linking and carbonization. While, high transparency is attributed to the amorphous nature of SK and its good compatibility with PC. This work demonstrates that SK is an efficient polymeric functional agent for fabricating transparent and flame-retardant PC and provides another idea for designing a sulfonate-group-containing flame retardant differing from traditional sulfonates for PC.