Gross Mechanisms of Smoke-Aerosol Production from Solids, Liquids, and Gases

摘要

All materials suffer thermal degradation at temperatures specific to that material. Organic materials generally degrade at relatively low temperatures (T/sub d/ < 600 exp 0 C) by a variety of mechanisms, depending on the molecular characteristics of the material, e.g., the material may simply evaporate, it may depolymerize with or without evaporation, or it may undergo surface reaction, forming an oxide or char on its exposed surface. Regardless of the mechanism, most organic materials will produce combustible gases and vapors above the heated surface, which, when mixed with air, ignites to flame. Both gases and aerosols are produced when organic materials are either thermally degraded (pyrolyzed) or burned. The evolution rate of these products depends upon the bulk temperature of fuel elements. This rate is maximum during active flaming combustion because of efficient heat feedback from flames to fuel. Results of thermogravimetric analyses of polyvinly chloride (PVC) and Teflon (polytetrafluorecthylene) are given. Factors that determine the dynamics of smoke transport are discussed. The rate of acid ion production as a function of radiant flux is given for three materials, small diameter PVC, large diameter PVC, are neoprene.