Exploratory studies in polymer ablation, ignition and extinction by the moving wire technique

Abstract

We present exploratory studies with the new moving wire technique. The principle of the method is to move the wire at a controlled speed through a stationary ignition source. Combustion is thus held fixed in laboratory coordinates, allowing unlimited observation time. Ignition and extinction are sharply reproducible transitions occurring at different residence times in the source (hysteresis). A variety of measurements are possible and a number of these are discussed in this paper. Temperature and O 2 profiles of the ignition source were taken to define the elements of the system. The characteristic residence times at ignition and extinction of three commercial polymer types (teflon, PVC and rubber) were measured as a function of the concentration of available O 2. High-speed movies of the ignition process provided an estimate of the propagation speeds involved. The diameters of orifices which quenched ignition were also investigated. Electron micrographs gave a qualitative idea of the degradation of the solid phase. The techniques presented sould provide a more detailed understanding of polymer flammability.