Moving wire technique studies of ablation,ignition and extinction of polymer flames

A new experimental method for studying the ablation, ignition and extinction of polymers exposed to flames and other ignition sources is presented. The technique is called the ‘Moving Wire Technique’. The polymer sample is carried on a wire support which is moved uniformity through the ignition source which is a flame in the example given. In the laboratory coordinate system, points along the path of the wire correspond to increasing residence time. The polymer combustion thus becomes a steady-state phenomena which can be studied at leisure with the improvements in precision associated with long time steady-state measurements. In addition to steady-state combustion, ignition and extinction transitions are observed whose onsets are sharp and can be accurately characterized in this system. In a favorable case, a reproducibility of a few parts per thousand is attained in determining critical ignition exposure times and extinction velocities. Results from initial studies of commercial Teflon® and poly-(vinylchloride) are presented. Measurements include critical ignition times and extinction velocities a function of free oxygen concentration. For poly-(vinylchloride), measurements are given of gas phase composition, mass loss of the polymer, and surface temperature of the polymer as a function of exposure time. A discussion is given of the relation of the results to other experiments and potential uses of the technique.