Fire Safety Science Digital Archive

Thin films of polyethylene, polystyrene and poly (methy1 methacrylate) were exposed t o the wake of a lean hydrogen-oxygen flat flame. Exposure was terminated at times ranging up to the point when flaming combustion began. The films were then analyzed by infrared spectroscopy. Oxidation of polyethylene and polystyrene occurred after a latency period but before ignition. The oxidation rate remained constant despite changes in flame-polymer separation and flame gas equivalence ratio. The latency period before oxidation observed for polyethylene depended on equivalence ratio and separation. No oxidation was observed with poly (methy1 methacrylate). A comparison of infrared spectra obtained by transmission through films with spectra obtained by internal reflection spectroscopy, demonstrated that oxidation of polyethylene and polystyrene before ignition is confined to within approximately 5 um of the exposed surface