Flame suppressant

Ammonium chloride has a number of iadustrial uses, most importantiy ia the manufacture of dry-ceU batteries, where it serves as an electrolyte. It is also used to make quarryiag explosives, as a hardener for formaldehyde-based adhesives, as a flame suppressant, and ia etching solutions ia the manufacture of ptinted circuit boards. Other appHcations iaclude use as a component of fluxes ia ziac and tin plating, and for electrolytic refining of ziac. 

Antimony trioxide and chlorinated paraffinic derivatives are common materials used as fire retardants, as are intumescent zinc (or calcium) borate, aluminium hydroxide and magnesium hydroxide. These inorganic materials, used as bulk fillers, act to reduce the fire hazard. Halogenated materials release chlorine, which then combines with the antimony trioxide to form the trichloride, which is a flame suppressant. 

The early patent disclosures have claimed the application of a wide spectrum of gas-evolving ingredients and phosphorus-based organic molecules as flame retarding additives in the electrolytes. Pyrocarbonates and phosphate esters were typical examples of such compounds. The former have a strong tendency to release CO2, which hopefully could serve as both flame suppressant and SEI formation additive, while the latter represent the major candidates that have been well-known to the polymer material and fireproofing industries.The electrochemical properties of these flame retardants in lithium ion environments were not described in these disclosures, but a close correlation was established between the low flammability and low reactivity toward metallic lithium electrodes for some of these compounds. Further research published later confirmed that any reduction of flammability almost always leads to an improvement in thermal stability on a graphitic anode or metal oxide cathode. 

The first attempts to reduce the temperature of detonation products of the explosive, and the second introduces flame-suppressing materials at and near, the face where blasting... 

For many elements, the atomization efficiency (the ratio of the number of atoms to the total number of analyte species, atoms, ions and molecules in the flame) is 1, but for others it is less than 1, even for the nitrous oxide-acetylene flame (for example, it is very low for the lanthanides). Even when atoms have been formed they may be lost by compound formation and ionization. The latter is a particular problem for elements on the left of the Periodic Table (e.g. Na Na + e the ion has a noble gas configuration, is difficult to excite and so is lost analytically). Ionization increases exponentially with increase in temperature, such that it must be considered a problem for the alkali, alkaline earth, and rare earth elements and also some others (e g. Al, Ga, In, Sc, Ti, Tl) in the nitrous oxide-acetylene flame. Thus, we observe some self-suppression of ionization at higher concentrations. For trace analysis, an ionization suppressor or buffer consisting of a large excess of an easily ionizable element (e g. caesium or potassium) is added. The excess caesium ionizes in the flame, suppressing ionization (e g. of sodium) by a simple, mass action effect ... 

Up to the time of writing in 1996, no satisfactory alternative to halon firefighting agents has been put on the market, although perfluoroalkylamines, which contain neither Br nor Cl but break down thermally to give the -H and -OH scavenger -CF3, appear to be effective flame suppressants.18... 

Larsen, E. R. Mechanism of flame inhibition II A new principle of flame suppression, Journal of Fire and Flammability/Fire Retardant Chemistry, 1975, 2, 5-20. 

The three methods for lead in air are essentially identical however, one should use S-341 because this method has been validated unlike P CAM 155 or P CAM 173. Although all the methods recommend 2-3 ml of nitric acid for wet ashing, the final solutions differ in that P CAM 155 recommends 1% nitric, P CAM 173 recommends 1% HC1, and S-341 recommends 10% nitric with EDTA 0.1 M to suppress phosphate, carbonate, iodide, fluoride, and acetate ion that cause flame suppression. EDTA is suggested in P CAM 173 where interferences are anticipated. Both S-341 and P CAM 173 use the 217.0 nm line which is twice as sensitive as the 283.3 nm line. Strong nonatomic absorption found when high concentrations of dissolved solid are present requires use of the background corrector. These two methods differ from P CAM 155 and those for biological analysis,... 

The flammability limits of hydrocarbon-type fuels in oxygen and inert gas atmospheres are a function of the inert gas and any fuel or oxygen in excess of that required by the stoichiometry of the combustion process. In systems where fuel content is fixed, inert material having a high heat capacity will be more effective at flame suppression than inert material having a low heat capacity. 

In the United States, suppression systems using Halon 1301 (bromotri-fluoromethane) (NFPA 69,1986) to quench the flames in industrial equipment are popular because damage to the product and to electrical components and other equipment is minimized. Halon 1301 is also used for flame suppression in areas occupied by people such as in computer rooms. Extinguishing flames successfully can usually be achieved at Halon 1301 concentrations of 5% for about 10 min., which usually allows people time to escape the area without harm. Halon 1301 is colorless and odorless and has minimal, if any, central nervous effects to people below a 7% concentration for exposures of 5 min. However, the decomposition products of Halon 1301 that may result from a fire are quite toxic. They have a characteristic sharp, acrid odor that provides a built-in warning system to people. Halon compounds are fluorocarbons which are being phased out of use because of environmental concerns. Substitutes are being developed and should be considered as they become available. 

To determine limits on flame suppression capability of this shield, thermal suppression studies have been conducted beyond those required for the safety approval proof tests mentioned previously ( ). 

Investigation of nonuniform venting has been initiated, but that work is not complete. Much work is required to develop the basic technology necessary to design optimal shields for flame suppression. 

Others calcium carbonate and sodium chloride for flame suppression, and paraffin and guncotton (nitrocellulose) for water resistance and gelling. 

Explosion suppression systems restrict and confine the fuel combustion in an early stage of an explosion by rapidly supplying flame suppressant into the fuel-air mixture. An explosion suppression system consists of the following elements ... 

The electronics industry desires improved flame suppressant additives for microelectronic encapsulants due to bromine induced failure. Epoxy derivatives of novolacs containing meta-bromo phenol have exhibited exceptional hydrolytic and thermal stability in contrast to standard CEN resins with conventional TBBA epoxy resins. When formulated into a microelectronic encapsulant, this stable bromine epoxy novolac contributes to significant enhancements in device reliability over standard resins. The stable bromine CEN encapsulant took about 30% more time to reach 50% failure than the bias pressure cooker device test. In the high temperature storage device test, the stable bromine CEN encapsulant took about 400% more time to reach 50% failure than the standard compound. Finally, the replacement of the standard resins with stable bromine CEN does not adversely affect the desirable reactivity, mechanical, flame retardance or thermal properties of standard molding compounds. 

This chapter overviews the various types of flame retardants that are added to POs. The chapter s content is influenced by recent trends in FR use, and it often focuses more on PP, given the market s needs for better FR solutions for this resin in particular. At the end of the chapter, a few case studies will illustrate recent developments in flame-suppressing additives. 

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