Intumescent flame retardants for polymers. IV. The polycarbonate–aromatic sulfonates system

Abstract

Abstract The mechanism of action of aromatic sulfonates as flame retardant (FR) agents on poly(bisphenol‐A carbonate) (PC) has been investigated. These compounds are capable of inducing a self‐extinguence in PC even when present in very low amounts (0.2–1%). Thermogravimetric and flash pyrolysis–GC–MS data show the thermal degradation rate of PC enhanced, and the distribution of the volatile pyrolysis products was modified by these additives. Oxygen Index (OI) and Nitrous Oxide Index (NOI) measurements indicate a FR condensed‐phase mechanism of these additives. Traces of polymer surface temperature against time, measured under forced flame conditions, show that the expanded carbon layer formed in the combustion of polycarbonate–aromatic sulfonate blends produces a heat insulating effect toward the undecomposed bulk. The overall evidence leads us to conclude that aromatic sulfonates cause the flame extinguishment in polycarbonate by an intumescent phenomenon.