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The autoignition temperature or kindling point of a substance is the lowest temperature at which it will spontaneously ignite in normal atmosphere without an external source of ignition, such as a flame or spark. This temperature is required to supply the activation energy needed for combustion. The temperature at which a chemical will ignite decreases as the pressure or oxygen concentration increases. It is usually applied to a combustible fuel mixture. Autoignition temperatures of liquid chemicals are typically measured using a 500 mL flask placed in a temperature controlled oven in accordance with the procedure described in ASTM E659.〔E659 – 78 (Reapproved 2000), "Standard Test Method for Autoignition Temperature of Liquid Chemicals", ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959〕 When measured for plastics, autoignition temperature can also be measured under elevated pressure and at 100% oxygen concentration. The resulting value is used as a predictor of viability for high-oxygen service. The main testing standard for this is ASTM G72.〔S. Grynko, "Material Properties Explained" (2012), ISBN 1-4700-7991-7, p. 46.〕 ==Autoignition equation== The time it takes for a material to reach its autoignition temperature when exposed to a heat flux is given by the following equation 〔Principles of Fire Behavior. ISBN 0-8273-7732-0. 1998.〕 where ''k'' = thermal conductivity (W/(m·K)), ''ρ'' = density (kg/m³), and ''c'' = specific heat capacity (J/(kg·K)) of the material of interest. is the temperature, in Kelvin, the material starts at (or the temperature of the bulk material), and is the heat flux (W/m²) incident to the material. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Autoignition temperature」の詳細全文を読む スポンサード リンク
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