Fire condensed phase

This volume does not address subjects such as toxic effects, explosions in buildings and vessels, runaway reactions, condensed-phase explosions, pool fires, jet flames, or structural responses of buildings. Furthermore, no attempt is made to cover the frequency or likelihood that a related accident scenario will occur. References to other works are provided for readers interested in these phenomena. 

Potential explosion phenomena include vapor cloud explosions (VCEs), confined explosions, condensed-phase explosions, exothermic chemical reactions, boiling liquid expanding vapor explosions (BLEVEs), and pressure-volume (PV) ruptures. Potential fire phenomena include flash fires, pool fires, jet fires, and fireballs. Guidelines for evaluating the characteristics of VCEs, BLEVEs, and flash fires are provided in another CCPS publication (Ref. 5). The basic principles from Reference 5 for evaluating characteristics of these phenomena are briefly summarized in this appendix. In addition, the basic principles for evaluating characteristics of the other explosion and fire phenomena listed above are briefly summarized, and references for detailed evaluation of characteristics are provided. 

The studies of fire-retardant action of halogenated compounds in the condensed phase were performed mostly on mixtures of chloroparaffin with vinyl polymers such as polyethylene,... 

Concluding, the destabilization of the above polymers by chloroparaffin should be beneficial in terms of fire retardance because it induces the formation of fuel at the temperature at which HC1 is evolved. Thus, the occurrence of a polymer additive interaction in the condensed phase... 

Mechanistic studies described above show that halogenated fire-retardant systems can act by a condensed phase mechanism that in some cases could be induced by a halogen-free compound. 

Costa, L. Camino, G. Luda, M. P. Mechanism of condensed phase action in fire retardant bismuth compound-chloroparaffin-polypropylene mixtures Part I—The role of bismuth trichloride and oxychloride, Polymer Degradation and Stability, 1986, 14(2), 159-164. 

Phosphorus-containing fire retardants can be active in the condensed phase or in the vapor phase, or in both phases.88 The relative predominance of the different mechanisms actually operating in a... 

Their fire-retardant mechanism is predominantly due to condensed phase action involving a combination of endothermic decomposition, water release, and oxide residue formation. 

In an attempt to look for alternatives to the use of halogenated fire retardants, which function in the gas phase, an approach has been pursued which controls the polymer flammability by modifying the condensed phase chemistry. Silica gel combined with potassium carbonate have been reported to be an effective fire retardant for a wide variety of common polymers, such as polypropylene, nylon, poly(methylmethacrylate), poly(vinyl alcohol), cellulose, and to a lesser extent, polystyrene and styrene-acrylonitrile.49 The cone calorimeter data shown in Table 8.5 indicate that the PHHR is reduced by up to 68% without significantly increasing the smoke or carbon monoxide levels during the combustion. 

Zinc borates are predominately a condensed phase fire retardant. In a halogenated system such as flexible PVC, it is known to markedly increase the amount of char formed during polymer combustion whereas the addition of antimony trioxide, a vapor-phase flame retardant, has little effect on char formation. Analyses of the char show that about 80%-95% of the antimony is volatilized, whereas the majority of the boron and zinc from Firebrake ZB remains in the char (80% and 60%, respectively).48-56 The fact that the majority of the boron remains in the condensed phase is in agreement with the fact that boric oxide is a good afterglow suppressant. The mode of action can be summarized in the following equation (not balanced). 

Fire-retarded materials functioning in the condensed phase, such as intumescent systems, form, on heating, foamed cellular charred layers on the surface, which protects the underlying material from the action of the heat flux or the flame. It is recognized that the formation of the effective char occurs via a... 

Pawlowski and Schartel92 have added 1 or 5 wt % of boehmite to blends of PC/ABS with PTFE and RDP or bisphenol A bis(diphenylphosphate). The release of water from AlOOH influences the decomposition of the material by enhancing the hydrolysis of PC and RDP. Consequently, the condensed action of RDP or BDP is perturbed. The reaction of the arylphosphate with boehmite replaces both the formation of anhydrous alumina and alumina phosphate on the one hand, and the cross-linking of arylphosphate with PC on the other hand, since less phosphate is available to perform condensed-phase action. The reaction with arylphosphate therefore decreases the char formation, but the formation of aluminum phosphate could enhance barrier properties. On the whole, even high levels of fire retardancy can be achieved (V-0 ratings) the combination of boehmite with arylphosphates acting in the condensed phase seems very complex, particularly when the host polymer can undergo hydrolysis reactions due to water release. 

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. 

Most physical phenomena in fires can be described as the transfer of heat and mass and chemical reactions in either gas or condensed phases. The physics of the fluid flow are governed by the conservation equations of mass, momentum, and enthalpy ... 

Solution of condensed-phase heat transfer equation is needed to analyze structural response to fires and simulate flame spread on solid surfaces. The solution of this conjugate heat transfer problem simulate is typical for fires, but rarely found in commercial CFD packages. Over the years, different techniques have been developed to tackle this problem. Since solid-phase heat transfer... 

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