Commercially available flame retardants

Commercially available flame retardants include chlorine- and bromine-containing compounds, phosphate esters, and chloroalkyl phosphates. Recent entry into the market place is a blend of an aromatic bromine compound and a phosphate ester (DE-60F Special) for use in flexible polyurethane foam (8). This paper describes the use of a brominated aromatic phosphate ester, where the bromine and phosphorus are in the same molecule, in high temperature thermoplastic applications. 

The focus of this program is to identify and characterize commercially available flame-retardants used in FR-4 printed circuit boards and their environmental, health, safety and environmental fate aspects.97 The project began in February 2006 and the program is currently in progress... 

Other chemical treatments may also be employed for more specific purposes for example, proprietary treatments, usually involving silicone or PTFE, enhance yam-to-yam or fibre-to-fibre lubricity during pulse or flex cleaning, and similarly, where flammability is a potential hazard, padding through commercially available flame retardant compounds may be necessary. 

Cone calorimetric evaluations of polymer-clay nanocomposites indicate that PHRR and mass loss rate (MLR) can be significantly reduced when compared to the pure polymer. However, in many cases, the ignition temperature is lower, the total heat released (THR) has not changed, and the total mass loss (TML) has not changed for the polymer-clay nanocomposites when compared to the pure polymer. An examination of the flame-retardant behavior of polymer-clay nanocomposites indicates that the presence of the clay delays the decomposition of polymer in the cone calorimeter test and does not prevent the decomposition. These observations in relation to the definitions listed above for flame retardants excludes clay from being considered to be a flame retardant in the same category as commercially available flame retardants. Because of these inadequacies, considerable effort has been made to identify synergies that may exist between commercial flame retardants and clay in polymer. 

C2HgNg H4O2P2 (60). The pyrophosphate is reported to be only soluble to the extent of 0.09 g/100 mL water, whereas melamine orthophosphate is soluble to 0.35 g/mL. The pyrophosphate is the most thermally stable. Melamine orthophosphate is converted to the pyrophosphate with loss of water on heating. AH three are available as finely divided soflds. AH are used commercially in flame-retardant coatings (qv) and from patents also appear to have utihty in a wide variety of thermoplastics and thermosets. A detaHed study of the thermal decomposition of the these compounds has been pubHshed (61). 

It is seen from Table 6.7 that, without exception, in a wide range of commercially available fire retardant polymers the incorporation of fire retardant additives into the formulation produces distinct improvements in LOI values and flammability and flame spread characteristics of the polymers listed. 

Brominated Additive Flame Retardants. Additive flame retardants are those that do not react in the appHcation designated. There are a few compounds that can be used as an additive in one appHcation and as a reactive in another. Tetrabromobisphenol A [79-94-7] (TBBPA) is the most notable example. Tables 5 and 6 Hst the properties of most commercially available bromine-containing additive flame retardants. 

DecabromodiphenylOxide. Decabromodiphenyl oxide [1163-19-5] (decabrom) is the largest volume bromiaated flame retardant used solely as an additive. It is prepared by the bromination of diphenyl oxide ia neat bromine usiag AlCl as a catalyst (32). The bromination may also be carried out ia an iaert solvent such as methylene dibromide [74-95-3] (33). The commercially available grades are >98% decabromodiphenyl oxide with the remainder being the nonabromo species. 

THPC—Amide—PoIy(vinyI bromide) Finish. A flame retardant based on THPC—amide plus poly(vinyl bromide) [25951-54-6] (143) has been reported suitable for use on 35/65, and perhaps on 50/50, polyester—cotton blends. It is appUed by the pad-dry-cure process, with curing at 150°C for about 3 min. A typical formulation contains 20% THPC, 3% disodium hydrogen phosphate, 6% urea, 3% trimethylolglycouril [496-46-8] and 12% poly(vinyl bromide) soUds. Approximately 20% add-on is required to impart flame retardancy to a 168 g/m 35/65 polyester—cotton fabric. Treated fabrics passed the FF 3-71 test. However, as far as can be determined, poly(vinyl bromide) is no longer commercially available. 

The use of copolymers is essentially a new concept free from low-MW additives. However, a random copolymer, which includes additive functions in the chain, usually results in a relatively costly solution yet industrial examples have been reported (Borealis, Union Carbide). Locking a flame-retardant function into the polymer backbone prevents migration. Organophosphorous functionalities have been incorporated in polyamide backbones to modify thermal behaviour [56]. The materials have potential for use as fire-retardant materials and as high-MW fire-retardant additives for commercially available polymers. The current drive for incorporation of FR functionality within a given polymer, either by blending or copolymerisation, reduces the risk of evolution of toxic species within the smoke of burning materials [57]. Also, a UVA moiety has been introduced in the polymer backbone as one of the co-monomers (e.g. 2,4-dihydroxybenzophenone-formaldehyde resin, DHBF). 

There are literally hundreds of flame retardants commercially available for nonwoven polyester and rayon. These can be subdivided into durable and nondurable. In this paper, non-durable means water soluble in room temperature water. Durable means able to withstand at least five washes in hot water with detergent. Flame retardants with performance somewhere in between, often called semi-durable, were not utilized in this study. Table III is a compilation of the flame retardants included in the study. Compositions include ... 

Once ignited they produced considerable amounts of heat and smoke. Flame retarded flexible PU foams became available in 1954-55, i.e. within a few years of flexible PU foams becoming available in commercial quantities(22). These FR PU foams contained trichloroethyl phosphate or brominated phosphate esters and resisted ignition from small flame sources. Unfortunately they may burn when subjected to a larger ignition source or when covered by a flammable fabric and may then produce as much heat and more smoke than the standard grade of PU foam(3). This was identified by UK room tests in the early 1970 s and has been confirmed more recently by furniture calorimeter tests at the NBS(21). 

Generally, flame retardants for engineering PET compositions are based on bromine-containing compounds (such as brominated polycarbonate, decabro-modiphenyl oxide, brominated acrylic, brominated polystyrene, etc.). Such compounds are available commercially (such as from the Ethyl Chemical Corporation, Great Lakes Chemical Corporation, Dead Sea Bromine Company, etc.) In addition, the flame-retardant package generally contains a synergist, typically sodium antimonate. PET may also be flame-retarded with diarylphosphonate, melamine cyanurate or red phosphorus. 

The above flame retardants, HMPN and TMP, along with another commercially available alkyl phosphate, triethyl phosphate (TEP), were systematically characterized by Xu et al. To quantify the flammability of the electrolytes so that the effectiveness of these flame retardants could be compared on a more reliable basis, these authors modified a standard test UL 94 HB, intended for solid polymer samples, and measured the self-extinguishing time (SET) instead of the universally used flame propagation rate. Compared with the UL 94 HB, this new quantity is more appropriate for the evaluation of the electrolytes of low flammability, since the electrolytes that are determined to be retarded or nonflammable by this method all showed zero flame propa-... 

Priest B. 2001. Brominated flame retardants Commercially available analytical standards. 

Reactive Flame Retardants. Table 2 lists the commercially available reactive flame retardants and intermediates. 

There are several classes of amine phosphates commercially available to flame retard a wide variety of polymeric substrates, both natural and synthetic.24 A classic example is the three variations of melamine phosphate melamine orthophosphate, dimelamine orthophosphate, and melamine pyrophosphate. Of these, the pyrophosphate is the least soluble and the most thermally stable. Melamine orthophosphate is converted to the pyrophosphate upon heating, with the loss of water. All the aforementioned variations are available as finally divided solids, are used commercially in coatings, and have utility in a wide variety of thermoplastics and thermosets (mostly presented in the patent literature). 

Pentaerythritol phosphate has an excellent char-forming ability owing to the presence of the pentaerythritol structure. The bis-melamine salt of the bis acid phosphate of pentaerythritol is also available commercially. This is a high melting solid that acts as an intumescent flame-retardant additive for polyolefins. Synergistic combinations with ammonium polyphosphates have also been developed primarily for urethane elastomers. Self-condensation of tris(2-chloroethyl) phosphate produces oligomeric 2-chloroethylphosphate. It has a low volatility, and is useful in resin-impregnated air filters, in flexible urethane foams and in other structural foams.11... 

A stannic chloride pentahydrate—ammonium bifluoride formulation for fireproofing wool is commercially available and used in New Zealand and Australia (20) (see Flame retardants for textiles). 

Many durable flame retardants for cotton have been developed to convey open-flame resistance [344,346,360,361]. The vertical flame test for determining the U.S. children s sleep-wear flammability (16 CFR 1615 and 1616) is a rather severe test and cotton fabrics require a FR treatment to pass the test. The test method requires treatments that are durable to 50 hot water wash and dry cycles. Currently there are relatively few commercially available FR chemistries that are durable under these conditions required today. Some of the reasons include low commercial availability of the chemicals, costs, safety concerns, process control issues, and difficulty in application. 

Aromatic polysulfones are a commercially important class of thermoplastic polymers [127]. They have highly desirable qualities such as chemical inertness, thermal stability, and flame retardency [128,129]. Although a number of methods are available for the synthesis of polysulfones [130,131,132], step polymerization methods are the most widely used industrially [127]. Polysulfones have been synthesized with the involvement of sulfonylium cations as propagating species. 

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