Phosphonium sulfonates as flame retardants for polycarbonate

Phosphonium sulfonates (PhSs) as flame retardants have been synthesized from organic sulfonates and triphenylphosphine as starting materials. The PhSs revealed good thermal stability and efficient flame retardancy for polycarbonate (PC). The LOI values increased with the increase of PhS-1 contents to PC and reached 33.7 when the PhS-1 content is 10 phr, and the V-0 rating can be achieved when only 5 phr PhSs are added. The cone calorimeter analysis indicated that the HRR and THR were reduced with the addition of PhSs to the PC matrix. The PhS bearing alkene group revealed highest LOI values and lowest peak HRR (pHRR) values for PC. The morphology of the residual chars after LOI test and the element content of the chars after CONE test were also investigated by SEM and EDX.