Autoignition test

Testing procedure. Temperature of specimen is kept constant at 430°C in the presence of air, and time to autoignition is measured. In another version, the oxygen atmosphere is modified, and the temperature of autoignition is recorded. 

Applications. Bound rubber is a measure of filler surface activity to the matrix, and it is considered as a factor in the estimation of filler reinforcement. 

Testing procedure. Small pieces of uncured rubber are immersed for several days at room temperature in a large excess of good solvent such as toluene. The sample in contact with solvent becomes divided into three parts polymer solution, mpi, solvent-dispersed filler particles with absorbed polymer chains, mpu, and solvent-swollen gel of filler particles connected through polymer chains, mpm. The fraction of polymer bound to filler is determined from the equation B = ( m 4- m m p where mp is total mass of polymer. The fraction of polymer not dispersed by solvent is given by the following equation G = m / m p. 

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The autoignition temperature is the minimum temperature required for self-sustained combustion in the absence of an external ignition source. The value depends on specified test conditions. Tht flammable (explosive) limits specify the range of concentration of the vapor in air (in percent by volume) for which a flame can propagate. Below the lower flammable limit, the gas mixture is too lean to burn above the flammable limit, the mixture is too rich. Additional compounds can be found in National Fire Protection Association, National Fire Protection Handbook, 14th ed., 1991. 

Some of the tests and criterion used to define fire resistance may be found in the Hterature (9). Additionally, the compression—ignition and hot manifold tests as defined in MIL-H-19457 and MIL-H-5606, respectively the Wick test as defined by Federal Standards 791, Method 352 flash point and fire point as defined in ASTM D92 autoignition temperature as defined in ASTM D2155 and linear flame propagation rate are defined in ASTM D5306 are used. 

PPS fiber has excellent chemical resistance. Only strong oxidising agents cause degradation. As expected from inherent resia properties, PPS fiber is flame-resistant and has an autoignition temperature of 590°C as determined ia tests at the Textile Research Institute. PPS fiber is an excellent electrical iasulator it finds application ia hostile environments such as filter bags for filtration of flue gas from coal-fired furnaces, filter media for gas and liquid filtration, electrolysis membranes, protective clothing, and composites. 

Tables 16 and 17 Hst tke analytical test methods for different properties of interest. The Manufacturing Chemists Association, Inc. (MCA) has pubUshed the Chemical Safety Data Sheet SD 63, which describes in detail procedures for safe handling of use of toluene (46). The Interstate Commerce Commission classifies toluene as a flammable Hquid. Accordingly, it must be packaged in authorized containers, and shipping must comply with ICC regulations. Properties related to safe handling are autoignition temperature, 536°C explosive limits, 1.27—7.0 vol % in air and flash point 4.4°C, closed cup.

Group D gases, but hexane or gasoline, owing to their lower autoignition temperatures. For Group C tests, ethylene can be used for all test stages. 

Important flammability characteristics are the lower and upper flammability limits, the flash point, the minimum ignition energy, the minimum oxygen concentration, and the autoignition temperature. Values of some of these properties are published for many compounds (NFPA, 1994). These numbers have typically been developed under standardized test conditions. Process conditions may influence their values. 

Nomenclature Autoignition Temp, °C Gap Test, 50%, Inches Impact Sensitivity Rifle ttuiiet Impact Test Vacuum Stability Test (ml/g/48hrs 120°) Refs... 

The chemistry involved in this explosively unstable system is reviewed [1]. The mechanism of the trigger reactions that initiate the exothermic decomposition of chlorate-sulfur mixtures has been studied. Mixtures containing 1-30% of sulfur can decompose well below the m.p. of sulfur, and addition of sulfur dioxide, the suspected chemical trigger, causes immediate onset of the reaction [2], Autoignition of stoichiometric mixtures can be as low as 115°C, with frictional sensitivity at 5N, the lowest load the test apparatus permitted. Both were dependent upon the history of the sulphur used [3],... 

ASTM E 659, Standard Test Method for Autoignition of Liquid Chemicals, American Society for Testing and Materials, Philadelphia, Pennsylvania, 1978. 

Another test (ASTM E-659) is available that can be used as a complement to the flash point test and involves determination of the autoignition temperature. However, the flash point should not be confused with the autoignition temperature, which measures spontaneous combustion with no external source of ignition. 

Measurement of autoignition temperature can vary based on the size of the vessel (i.e., the test apparatus) holding the vapor and the strength of the ignition source. Because of these factors, there is often some variability in quoted autoignition temperatures. The convention is to use the lowest value found in literature. 

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