Combustion condensed phase

Price D, Anthony G, Carty P. Introduction Polymer combustion, condensed phase pyrolysis and smoke formation. In Fire Retardant Materials. Horrocks AR, Price D, Eds. Woodhead Publishing Cambridge, U.K., 2001 chap. 1, pp. 1-30. 

Phosphoms-containing additives can act in some cases by catalyzing thermal breakdown of the polymer melt, reducing viscosity and favoring the flow or drip of molten polymer from the combustion zone (25). On the other hand, red phosphoms [7723-14-0] has been shown to retard the nonoxidative pyrolysis of polyethylene (a radical scission). For that reason, the scavenging of radicals in the condensed phase has been proposed as one of several modes of action of red phosphoms (26). 

Powling (P7) recently reported on the results of an extensive study of the combustion characteristics of ammonium perchlorate-based composite propellants. The nature of the chemical processes taking place at the solid-gas interface and the possibility of heat release in the condensed phase were considered. Although the evidence is that some heat release is likely to occur within the solid surface, Powling found that the combustion in all pressure regions appears to be dominated by gas-phase reactions. 

When pressure-decay rates less than critical are employed, the gas-phase combustion zone is removed from the propellant surface and extinguished, but not the ignition from within the condensed phase. Therefore, the temperature of the surface material will be above the autoignition temperature, and steady-state combustion will eventually be initiated. This mechanism is consistent with the observation that the luminosity of the combustion zone can vanish without combustion having been completely terminated. 

Additional events of concern that may or may not involve flammable or combustible materials are condensed-phase explosions, uncontrolled chemical reactions, boiling liquid expanding vapor explosions (BLEVEs),... 

Identify the inventories of flammable and combustible materials within the process plant and the physical conditions under which they are contained. Similarly, identify other materials or process conditions that can result in explosion events, including condensed-phase explosions, physical explosions, or uncontrolled chemical reactions. 

What about measurements of enthalpies of combustion of condensed phase species 49 and 50 and accompanying enthalpies of vaporization Enthalpies of formation of the gaseous hydrocarbons can be directly obtained from these studies as well. There are two recent studies that provide us with useful information. The first42 results in the values of 104.6 0.6 and 104.8 0.6 kJmol-1 respectively. The second accompanies the earlier cited cyclic bisallene (and polycyclic monoolefin) study, in which the authors20... 

The desired enthalpy of formation of 6,6-dimethylfulvene was determined by Roth citing measurement of hydrogenation enthalpies, and chronicled by Pedley citing enthalpies of combustion and vaporization. The two results differ by 7 kJ mol-1. We have opted for Roth s value because it is in better agreement with a value calculated using Roth s force field method. It is also to be noted that measurement cited by Pedley for the neat condensed phase could be flawed by the presence of partially polymerized fulvene and neither elemental abundance of the compound nor analysis of the combustion products would have disclosed this. Likewise, the measured enthalpy of vaporization would not have necessarily uncovered this contaminant. 

Burning rate is strictly defined as the mass rate of fuel consumed by the chemical reaction, usually but not exclusively in the gas-phase. For the flaming combustion of solids and liquids, the burning rate is loosely used to mean the mass loss rate of the condensed phase fuel. However, these two quantities - mass loss rate and burning rate - are not necessarily equal. In general,... 

The control volume in the gas phase (Figure 9.19) is considered as stationary, steady and responds fast to any changes transmitted from the condensed phase. A portion of the water used in suppression is evaporated in the flame. The flame is a thickness of <5R within the boundary layer. Kinetic effects are important in this region where essentially all of the combustion occurs. The conservation relationships follow ... 

This part includes a discussion of the main experimental methods that have been used to study the energetics of chemical reactions and the thermodynamic stability of compounds in the condensed phase (solid, liquid, and solution). The only exception is the reference to flame combustion calorimetry in section 7.3. Although this method was designed to measure the enthalpies of combustion of substances in the gaseous phase, it has very strong affinities with the other combustion calorimetric methods presented in the same chapter. 

To our knowledge, the question of the standard state corrections in DSC experiments has never been addressed. These corrections may in general be negligible, because most studies only involve condensed phases and are performed at pressures not too far from atmospheric. This may not be the case if, for example, a decomposition reaction of a solid compound that generates a gas is studied in a hermetically closed crucible, or high pressures are applied to the sample and reference cells. The strategies for the calculation of standard state corrections in calorimetric experiments have been illustrated in chapter 7 for combustion calorimetry. 

PET can be made flame retardant (FR-PET) by halogenated additives in combination with synergists such as antimony compounds (which impart no flame inhibition by themselves). During combustion, volatile antimony trihalide is formed in the condensed phase and transported to the gas phase. Failure of this flame retardant in PET compounds can occur, however, due to the formation of stable metal halides such as the following ... 

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