Hydrophobic Micro-crosslinked Sulfonated Polystyrene Flame Retardant for Simultaneous Fire safety, Transparency and High Performance of Polycarbonate

Sulfonate is considered to be the best flame retardant, which can endow polycarbonate (PC) excellent flame retardancy with low addition. Unfortunately, the water absorption and solubility of sulfonate will increase the cost of transportation and storage. In addition, sulfonate flame retardant is easy to migrate and precipitate from PC composites resulting in a negative impact on the sustainable use of PC materials. To ameliorate this issue, a sulfonate flame retardant (CSPS) with unparalleled hydrophobicity and thermal stability was synthesized through the incorporation of sodium p-styrene sulfonate as the main chain of crosslinked polystyrene. The PC/CSPS composites could pass UL 94 test V-0 rating with 0.3 wt% CSPS addition, and the LOI is increased from 24.5% to 31.4%. Simultaneously, the PC/CSPS composites preserve their initial transparency. Moreover, the combustion test results indicated that the peak of heat release rate (PHRR) and the peak of smoke production rate (PSPR) of PC/CSPS-0.3 composites decreased by 40% and 41% respectively, and the time to reach PHRR and PSPR increased by 35.8% and 56.5% respectively. These results were attributed to the catalytic char formation and gas phase limitation of CSPS, which made PC composites with higher fire safety. Importantly, the PC/CSPS-0.3 composites can maintain tensile strength similar to that of PC. This research proposes a simplified and efficient methodology for fabricating PC composites with outstanding water resistance, flame retardancy, transparency, and mechanical fortitude, which is of considerable importance for the application of PC composites in emerging fields.