Cooling flame retardancy

Antimony Oxide as a Primary Flame Retardant. Antimony oxide behaves as a condensed-phase flame retardant in cellulosic materials (2). It can be appHed by impregnating a fabric with a soluble antimony salt followed by a second treatment that precipitates antimony oxide in the fibers. When the treated fabric is exposed to a flame, the oxide reacts with the hydroxyl groups of the cellulose (qv) causing them to decompose endothermically. The decomposition products, water and char, cool the flame reactions while slowing the production and volatilization of flammable decomposition products (see Flaa retardants for textiles). 

Organophosphoms compounds, primarily phosphonic acids, are used as sequestrants, scale inhibitors, deflocculants, or ion-control agents in oil wells, cooling-tower waters, and boiler-feed waters. Organophosphates are also used as plasticizers and flame retardants in plastics and elastomers, which accounted for 22% of PCl consumed. Phosphites, in conjunction with Hquid mixed metals, such as calcium—zinc and barium—cadmium heat stabilizers, function as antioxidants and stabilizer adjutants. In 1992, such phosphoms-based chemicals amounted to slightly more than 6% of all such plastic additives and represented 8500 t of phosphoms. Because PVC production is expected to increase, the use of phosphoms additive should increase 3% aimually through 1999. 

Flame retardants (qv) are incorporated into the formulations in amounts necessary to satisfy existing requirements. Reactive-type diols, such as A/ A/-bis(2-hydroxyethyl)aminomethylphosphonate (Fyrol 6), are preferred, but nonreactive phosphates (Fyrol CEF, Fyrol PCF) are also used. Often, the necessary results are achieved using mineral fillers, such as alumina trihydrate or melamine. Melamine melts away from the flame and forms both a nonflammable gaseous environment and a molten barrier that helps to isolate the combustible polyurethane foam from the flame. Alumina trihydrate releases water of hydration to cool the flame, forming a noncombustible inorganic protective char at the flame front. Flame-resistant upholstery fabric or liners are also used (27). 

Substances applied to or incorporated in a combustible material (e.g. organic polymers, nylon, vinyl and rubber, etc.) to reduce flammability. Act by retarding ignition, control/douse burning, reduce smoke evolution. Slow down or interrupt the self-sustained combustion cycle when the heat-flux is limited. Flame retardants (FRs) improve the combustion behaviour and alter the combustion process (cool, shield, dilute, react) so that decomposition products will differ from nonflame retarded articles. FRs are usually divided into three classes ... 

Ellis and coworkers studied the effect of lead oxide on the thermal decomposition of ethyl nitrate vapor.P l They proposed that the surface provided by the presence of a small amount of PbO particles could retard the burning rate due to the quenching of radicals. However, the presence of a copper surface accelerates the thermal decomposition of ethyl nitrate, and the rate of the decomposition process is controlled by a reaction step involving the NO2 molecule. Hoare and coworkers studied the inhibitory effect of lead oxide on hydrocarbon oxidation in a vessel coated with a thin fQm of PbO.P l They suggested that the process of aldehyde oxidation by the PbO played an important role. A similar result was found in that lead oxide acts as a powerful inhibitor in suppressing cool flames and low-temperature ignitions.P l... 

Fogging This test is a special case of test chamber examination-SVOCs such as plasticizers and flame retardants are precipitated inside the chamber on a cooled surface. The method had initially been developed for examining automotive parts in order to determine the portion of fogging-active substances. It can also be used for examining other products used indoors. The fogging value (in Xg), usually determined over a 14-day period, is a characteristic for the SVOC quantity which can be expected to condense on cold indoor surfaces. The fogging method is based on a convention. If results are to be compared, the studies must be carried out in an identical manner (Uhde et al., 2001 Wensing, Uhde and Salthammer, 2005). 

Triphenylphosphate is a colorless, odorless, crystalline solid (mp, 49°C bp, 245°C). It is moderately toxic. A similar, but much more toxic, compound is tri-o-cresyl-phosphate (TOCP), an aryl phosphate ester with a notorious record of poisonings.3 Before its toxicity was fully recognized, TOCP was a common contaminant of commercial tricresylphosphate. Tricresylphos-phate is an industrial chemical with numerous applications and consists of a mixture of phosphate esters in which the hydrocarbon moieties are meta and para cresyl substituents. It has been used as a lubricant, gasoline additive, flame retardant, solvent for nitrocellulose, plasticizer, and even a cooling fluid for machine guns. Although modem commercial tricresylphosphate contains less than 1% TOCP, contaminant levels of up to 20% in earlier products have resulted in severe poisoning incidents. 

Mono- and diphosphonium halides have been found to be flame retardants for plastic materials. Their effectiveness can be related to the formation of various active phosphorus compounds, as well as to many of the postulated mechanisms for flame retardant action. The compounds are postulated to be effective because they decompose on ignition to thermally stable phosphine oxides or phosphonic acids which, in turn, are decomposed to continuous films of phosphate glass. In addition, the phosphonium halides form alkyl halides which cool the flame and/or form halogen acids which are fame retardants. 

During or at the end of the EPS production, a number of additives can be incorporated to improve process and application properties. Additives can include nucleation agents, flame retardants, fast-cool agents, anti-lump and anti-static agents, stabilizers, plasticizers, pigments, etc. Some of the more important additives and their functions are described in more detail below. 

A similar sharp transition has been noted [43] when formaldehyde is the additive. Furthermore, there is an accompanying shift of the cool flame limits to higher pressures and/or temperatures. Formaldehyde also interferes with the cool flame combustion of acetaldehyde in flow systems [7]. Its addition retards the development of the cool flame but promotes the second stage this promotion may be caused by the occurrence of... 

The flame-retardant effect of magnesium hydroxide and ATH is based on the endothermic decomposition to magnesium or aluminum oxide, see reactions (11.1) and (11.2). This decomposition effectively acts as a heat sink cooling the surface of the polymer. 

HDPE filled with a flame-retardant ATH (aluminum trihydrate) showed the ignition temperature of 445°C (833°F). The 10°C delay was caused by ATH, which releases water vapor at about 180-240°C (360-460°E), which that in turn cools down the material. 

When the material contains some flame retardants, for example, ATH, its ignition point often shifts np. ATH, as it will be explained below in more detail, releases water at a certain temperature level. Water cools down the material and increases an apparent ignition time it also reduces the heat produced by the burning material and therefore qnenches flames. 

The heating and cooling system consists of an inert hydrocarbon mixture. The height of the system is around 2.5 meters (to the top of the stirrer) and 5-6 meters in total. The metal-clad pipes on the right of the reactor are the condensers. The box is equipped with a direct venting system and a flame-retarding valve for safe removal of the hydrogen. 

Blends produced under the Eref trade name include both alloys rich in PP and alloys rich in PA where PA is PA-66 or PA-mXD6 (a semicrystalline PA, made by polycondensation of m-xylylenediamine and adipic acid). A compati-bilizer is added in order to provide optimal adhesion between PP and PA. Injection molding machines used for injecting PA are recommended, with peripheral screw speeds of 3-10 m/min. Cooling time can be estimated as 2.5xe seconds where e is the wall thickness in mm. Melt temperature for flame retarded grades must be well controlled and not exceed 270°C. 

Require high loading to achieve modest flame retardance. Low cost. Low smoke advantage. Nontoxic. Multifunctional extender. Flame-retardant mechanism endothermic (heat-absorption) cooling of flame upon release of water of hydration... 

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