Novel sulfonate-containing halogen-free flame-retardants: effect of ternary and quaternary sulfonates centered on adamantane on the properties of polycarbonate composites

In order to find a more environmentally friendly flame retardant, we have designed a novel halogen-free flame-retardant (FR) system consisting of ternary and quaternary sulfonates centered on adamantane. They are named 1,3,5-tri(phenyl-4-sodium sulfonate) adamantane (AS(3)) and 1,3,5,7-tetrakis(phenyl-4-sodium sulfonate) adamantane (AS(4)), respectively. Both kinds of FRs were synthesized and compounded with polycarbonate (PC) to study their effects on the properties of PC composites. The results show that the new FR system can improve PC flame retardancy efficiently, and has mechanical strength advantages as well. The PC composites with only 0.1 wt% AS(3) or 0.08 wt% AS(4) can pass vertical burning tests (UL94) V-0 level, with increasing the value of limiting oxygen index (LOI) to 31.2% or 32.3%. Moreover, they can maintain ideal mechanical properties compared to neat PC simultaneously. Finally, the flame retardant mechanism of this system was verified via thermal analysis, morphology and chemical structure analysis of the char residues.