Autoignition temperature data and scaling for amide solvents

Autoignition temperature tests using the ASTM E659 test method have been conducted for N,N-dimethylacetamide (DMAC) and N,N-dimethylformamide (DMF) in test vessels with volumes of 0.5 l, 5 l, and 12 l. Tests were conducted at three different laboratories yielded good agreement (standard deviation with 5 °C) in all cases except for DMAC in the 0.5 l test vessel (standard deviation of 23 °C). Scaling correlations have been developed for the decrease of autoignition temperature with increasing volume and for increasing values of the vessel volume to surface area ratio. The variations for DMAC are steeper than the literature values for almost all other combustible liquids. Cool flames were observed for DMAC at temperatures as much as 44 °C below the autoignition temperature and for DMF at temperatures as much as 171 °C below its autoignition temperature. The DMF cool flame temperatures in the 5-l and 12-l test vessels are approximately equal to the DMF autoignition temperature in a closed 12-l test vessel. Gas samples taken after the cool flame and hot flame tests reveal the presence of high concentrations of diamines and dimethylamino acetonitrile, and small concentrations of many other partial decomposition/oxidation components.