Propagators oxygen requirements

Figure 9.4 illustrates the effect of pressure on minimum oxygen requirements for propagation of natural gas, ethane, and propane in air-nitrogen mixtures.4 The Min02 for natural gas at room temperature and atmospheric pressure is 12%. The Min02 for propane at room temperature and atmospheric pressure is 11.5%. 

The conditions used for these experiments indicate that a greater effect can be created by metering in the substrate. Oxygen is required in these incubations to reoxidize the laccase. It might also react with laccase generated radicals and propagate oxygen free radicals that could be additional reactants. 

Definition of Dust E losion A dust explosion is the rapid combustion of a dust cloud. In a confined or nearly confined space, the explosion is characterized by relatively rapid development of pressure with a flame propagation and the evolution of large quantities of heat and reaction products. The required oxygen for this combustion is mostly supphed oy the combustion air. The condition necessaiy for a dust explosion is a simultaneous presence of a dust cloud of proper concentration in air that will support combustion and a suitable ignition source. 

Polymerization inhibitors are key additives which prevent premature gelation of the adhesive. The foimulator must carefully balance shelf stability and the required cure on demand. Due to its high propagation rate, MMA is difficult to inhibit. Some comments on specific inhibitors follow. The most common inhibitor to be found in component monomers is 4-methoxyphenol, which is also called the methyl ether of hydroquinone. This inhibitor is effective only in the presence of oxygen. A mechanism has been proposed, and is illustrated in Scheme 13 [128]. 

Dithiols and dienes may react spontaneously to afford dithiols or dienes depending on the monomer dithiol ratio.221 However, the precise mechanism of radical formation is not known. More commonly, pholoinilialion or conventional radical initiators are employed. The initiation process requires formation of a radical to abstract from thiol or add to the diene then propagation can occur according to the steps shown in Scheme 7.17 until termination occurs by radical-radical reaction. Termination is usually written as involving the monomer-derived radicals. The process is remarkably tolerant of oxygen and impurities. The kinetics of the tbiol-ene photopolymerizalion have been studied by Bowman and... 

The LFL is based on fuel in air. However, oxygen is the key ingredient and there is a minimum oxygen concentration required to propagate a flame. This is an especially useful result, because explosions and fires can be prevented by reducing the oxygen concentration regardless of the... 

The results of the calculation could not distinguish hydroxyl or propyl radicals as the desorbed species, since they produced very similar product distributions. This is because they were both involved in the chain propagation reactions. Since the desorption of a hydroxyl radical required cleavage of metal-oxygen bonds in the oxide lattice, it would be energetically less favorable. Thus it was concluded that propyl radicals were the most likely desorbed species. 

The self-sustaining decomposition is a phenomenon whereby the decomposition is initiated by a hot spot, and then propagates through to the solid with a velocity of some millimeters to centimeters per second. The decomposition does not require oxygen, so it cannot be avoided by using an inert atmosphere. 

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