Flammability characteristics

The discussion below pertains to various aspects of flammability that are relevant to understanding flame propagation. 

Flammable limits are affected by both temperature and pressure. In general, as the temperature of a gas mixture increases, the size of the flammability zone increases. For mixtures in air, the UFL increases and the 

LFL decreases, which broadens the range over which the mixtnre is flam-mahle. In general, pressnre has little effect on the LFL, except at low pres-snres (e.g., ahont 100 inmHg for methane) where comhnstion is not possible. As the pressnre increases, the UFL generally increases, broadening the flammability range. Eqnations are available for calcnlating the effect of temperatnre on the LFL and UFL, and pressnre on the UFL (Coward and Jones 1952, Zabetakis 1965). 

Both LFL and UFL valnes for mixtnres can be estimated by nse of the Le Chatelier eqnation (Growl and Lonvar 1990). However, the methods have some limitations with respect to calcnlating the UFL for certain mixtnres. Britton (1996) determined that the eqnation does not apply to the UFL of mixtnres containing decomposable components snch as ethylene oxide or to mixtnres containing ethyl ether. Mashnga and Growl (2000) discnss the derivation of Le Chatelier s mixing rnle for flammable limits. 

Flammable limits are important as they indicate the range of concentrations within which a comhnstion reaction may occnr. If a concentration of a fnel-oxidant mixtnre can be maintained below the LFL or above the UFL, then there is no possibility of flame propagation. Fignre 3-10 (page 32) is a typical flammability diagram with the flammable zone between the LFL and the UFL indicated. 

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Many grades of acetal resins are Hsted in Underwriters Eaboratories (UL) Kecogni d Component Directory. UL assigns temperature index ratings indicating expected continuous-use retention of mechanical and electrical properties. UL also classifies materials on the basis of flammability characteristics homopolymer and copolymer are both classified 94HB. 

M. G. Zabetakis, Flammability Characteristics of Combustible Gases and Vapors, Bulletin 627, U.S. Bureau of Mines, Washington, D.C., 1965. 

Flammability characteristics (1) of the four butanols are given ia Table 5. ... 

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. 

Bond, J. 1991. Sources of Ignition-Flammability Characteristics of Chemicals and Products. Butterworth-Hememann, Boston, MA. 

Zabetakis, M. G. 1965. Flammability characteristics of combustible gases and vapwrs. Bureau of Mines Bulletin 627. Pittsburgh. 

Hydrocarbons such as propane and butane are being successfully used as replacement and new refrigerants for R12 systems. They obviously have flammable characteristics which have to be taken into account by health and safetyrequirements. However, there is a market for their use in sealed refrigerant systems such as domestic refrigeration and unitary air-conditioners. 

Zabetakis, K.S., Flammability characteristics of combustible gases and vapors, U.S. Department of Mines Bulletin, No. 627, 1965. 

Boleij, J.S.M. et al. (1994) Occupational Hygiene of Chemical and Biological Agents, Elsevier Science Ltd, Amsterdam. Bond, J. (1991) Sources of Ignition-Flammability Characteristics of Chemicals and Products. Butterworth-Heinemann, Oxford. 

Zabetakis, 1965 Flammability Characteristics of Combustible Gases and Vapours, Zabetakis, M. G., Washington, US Bureau of Mines, 1965... 

D. E. Stuetz, Symposium on the Flammability Characteristics of Polymeric Materials, University of Utah, June 21-26, 1971. 

PMMA - Red Phosphorus System. The initial reaction that was investigated was that between PMMA and red phosphorus (4-51. Phosphorus was chosen since this material is known to function as a flame retardant for oxygen-containing polymers (1 2). Two previous investigations of the reaction of PMMA with red phosphorus have been carried out and the results are conflicting. Raley has reported that the addition of organic halides and red phosphorus to PMMA caused moderate to severe deterioration in flammability characteristics. Other authors have reported that the addition of chlorine and phosphorus compounds are effective flame retardant additives (12). 

WHANG PEARCE Polymers with Improved Flammability Characteristics 267... 

Flammability Characteristics of Fiber-Reinforced Composite Materials... 

The objective of the study was to assess the flammability characteristics of FRC materials using small-scale experiments. 

AMTL and FMRC have been performing research to quantify the flammability characteristics of FRC materials which are enumerated in this paper. 

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