Mechanisms of action of phosphorus based flame retardants in acrylic polymers

The fire-induced degradation chemistry of a random copolymer of methyl methacrylate with a flame retardant phosphate–methacrylate comonomer has been studied to gain an insight into the mechanisms of fire retardancy in the model system and thus help to provide a fundamental basis for the further development of fire resistant poly(methyl methacrylate)s. To obtain information about the fire-induced condensed phase degradation chemistry of the model system, surface analytical techniques have been exploited to assemble a picture of the chemical nature of the surface char present on fire-tested samples. A number of analytical techniques were utilized in these studies, including X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ionization mass spectroscopy (TOF-SIMS), nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform infrared (IR) spectroscopy. In addition, the model flame retardant copolymer was subjected to combined thermogravimetric and evolved gas analysis (TGA-EVA) to identify the chemical nature of the volatile species evolved upon thermal degradation. Using the analytical data accumulated, a mechanism is proposed for the condensed phase mode of action of the phosphate-based flame retardant in the model methacrylate copolymer.