Self-ignition temperature

The self-ignition temperature of PVF film is 390°C. The limiting oxygen iadex (LOI) for PVF is 22.6% (98), which can be raised to 30% ia antimony oxide-modified film (99). Hydrogen fluoride and a mixture of aromatic and aUphatic hydrocarbons (100) are generated from the thermal degradation of PVF. Toxicity studies, ie, survival and time to iacapacitation, of polymers, ceUulosics (101,102), and airplane iaterior materials (103) expose... 

Hydrazine is an unstable substance because of its positive enthalpy of formation. It decomposes when heated. The decomposition can cause an inflammation even in the absence of air. It can also combust spontaneously in the presence of various materials from clothes to soil (see tables in Part Three the self-ignition temperatures vary according to the materials in contact with hydrazine). Also, violent decomposition of hydrazine in a steel reactor occurs when in a carbon dioxide atmosphere. 

The interaction of disulphide with oxygen can be very dangerous. This compound has a very low self-ignition temperature (see tables in Part Three). When rust is present it can cause the mixture to detonate by catalysing the oxidation reaction. 

Pellistors are used to detect flammable gases like CO, NH3, CH4 or natural gas. Some flammable gases, their upper and lower explosion limits and the corresponding self-ignition temperatures are listed in Tab. 5.1. This kind of gas sensor uses the exothermicity of gas combustion on a catalytic surface. As the combustion process is activated at higher temperatures, a pellistor is equipped with a heater coil which heats up the active catalytic surface to an operative temperature of about 500 °C. Usually a Platinum coil is used as heater, embedded in an inert support structure which itself is covered by the active catalyst (see Fig. 5.33). The most frequently used catalysts are platinum, palladium, iridium and rhodium. 

Tab. 5.1 Explosion limit and self-ignition temperature of some flammable gases [9],...

Gross, D. and Robertson, A.F., Self-ignition temperatures of materials from kinetic-reaction data, J. Research National Bureau of Standards, 1958, 61, 413-7. 

Setchkin, N.P., Self-ignition temperature of combustible liquids, J. Research, National Bureau of Standards, 1954, 53, 49-66. 

Autoignition. If the temperature of a flammable gas-air mixture is raised in a uniformly heated apparatus, it eventually reaches a value at which combustion occurs in the bulk gas. This temperature is defined as the spontaneous ignition temperature (SIT) or autoignition temperature (AIT). The gas-air mixture that has the lowest ignition temperature is called by various names, such as the minimum AIT, the minimum spontaneous ignition temperature, and the self-ignition temperature.27 Usually the AIT reported in the literature is the minimum AIT. 

NOTE 2 The criteria are based on the self-ignition temperature of charcoal, which is 50°C for a sample cube of 27 rrf. Substances and mixtures with a temperature of spontaneous combustion higher than 50°C for a volume of 27 m should not be assigned to this hazard class. Substances and mixtures with a spontaneous ignition temperature higher than 50°C for a volume of 450 litres should not be assigned to hazard Category 1 of this hazard class. 

D. Gross and A. F. Robertson, Self-Ignition Temperatures of Materials from Kinetic-Reaction Data, J. Research Natl. Bur. Standards, 61, 413-417 (1958). 

Table XXXI.—Effect of Compounds on the Self-Ignition Temperature of Gasoline Wccrman). ...

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