Brominated flame retardant

Marsh et al. [36] examined analogous p-hydroxybromodiphenyl ethers and their binding to TR. The diphenyl ethers (brominated or not) bind much less avidly than T3 or T4, probably owing to the absence of the 4-carboxyl group. 4-Hydroxydiphenyl ether had the lowest affinity for THR. Within the brominated diphenyl ethers, the lowest binding was observed with the unsubstituted 4-hydroxydiphenyl ether, followed by bromine substitution in the 3 - and 5-positions, and followed by substitution by iodine. 

The term brominated flame retardant (BFR) incorporates more than 175 different types of substances, which form the largest class of flame retardants other classes are phosphorus-containing, nitrogen-containing, and inorganic flame retardants (Bimbaum and Sttaskal 2004). The major BFR substances in use today (depicted in Fig. 4.6) are tetrabromobisphenol A (TBBPA), hexabromocyclododecane (HBCD), and mixtures of polybrominated diphenyl ethers (PBDEs) (namely, deca-bromodiphenyl ether (DBDE), octabromodiphenyl ether (OBDE), and pentabro-modiphenyl ether (pentaBDE)). 

BFRs have been added to various products (e.g., electrical appliances, building materials, vehicle parts, textiles, furnishings) since the 1960s, in growing rates (15-fold from the mid-1960s to 2003 DePierre 2003). BERs usually are classified as semi-volatile and hydrophobic, but these properties vary due to the large diversity of this group of compounds. 

HBCD distribution in the environment and its effects on humans were discussed in a review by Covaci et al. (2006). HBCD was reported to be capable of inducing cancer by a nonmutagenic mechanism (Helleday et al. 1999 Yamada-Okabe et al. 2005). Similar to the BPDEs, HBCD is considered capable of disrupting the thyroid 

Bromine radicals released during thermal decomposition of BFRs act as efficient electron scavengers to inhibit combustion. Other flame retardants that utilize chlorination or phosphorylation to inhibit combustion have been developed however, current usage of these materials is insignificant compared with brominated reagents. Methodologies used for the analysis 

BFRs can be categorized as additive or reactive materials. Additive BFRs are incorporated in the polymer as a physical mixture and are not chemically bonded. Reactive BFRs are selected to copolymerize with other polymer constituents and are typically more resistant to leaching into the environment than polymers formulated with additive BFRs. 

BDEs were the first widely used BFRs, available as three technical mixtures with different degrees of bromination. PentaBDE consists of a mixture of BDE-99/47/100/153/154 congeners octaBDE consists of a mixture of BDE-183/197/196/207 congeners, and decaBDE consists of BDE-209/206. The production of polybrominated biphenyls (PBBs), pentaBDE, and octaBDE technical mixtures has been discontinued due to bans or restrictive measures imposed by the EU, the EPA, and state governments in the United States [91,92]. Of the three BDE technical mixtures, only decaBDE remains in production. 

Decabromodiphenylethane was introduced in the mid-1980s as an alternative to decaBDE, and its usage is expected to increase as decaBDE is phased out. Because products containing penta-, octa-, and decaBDE BERs are in existence, measurement of the various BDE congeners is still relevant. 

The analysis of BDEs has been reviewed by Stapleton [10] Kierkegaard, Sellstrom, and McLachlan [93] Wang and Li [90] and Covaci et al. [88]. Because BDEs have similar physical and chemical properties to polychlorinated biphenyl congeners (and, in fact, the same naming conventions are used for BDEs as PCBs), similar methods have also been used for their analysis. With the exception of the higher brominated BDEs (i.e., certain octa-, nona-, and decaBDEs), gas chromatography-mass spectrometry (GC—MS) and related techniques are the methods of choice for determination of BDEs from complex samples [6,94]. Decabromodiphenyl ether, BDE-209, is thermally unstable and is observed to debrominate during analysis by GC consequently, LC methods of analysis are preferred. LC methods are also preferred for BDE metabolites and transformation products, which are often sufficiently polar to require derivitization for analysis by GC derivitization is not required for LC analysis. 

BFRs are one of the last classes of halogenated compounds that are still being produced worldwide and used in high quantities in many applications. In order to meet fire safety regulations, flame retardants (FRs) are applied to combustible materials such as polymers, plastics, wood, paper, and textiles. Approximately 25% of all FRs contain bromine as the active ingredient. More than 80 different aliphatic, cyclo-aliphatic, aromatic, and polymeric compounds are used as BFRs. BFRs, such as polybrominated biphenyls (PBBs), polybrominated diphenyl ethers (PBDEs), hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA), have been used in different consumer products in large quantities, and consequently they were detected in the environment, biota, and even in human samples [26, 27]. 

Due to the toxicological effect of PBDEs, the production and use of penta-, octa-, and deca-BDE mixtures have been banned in Europe. Moreover, and in response to increasing international regulations on BFR formulations, alternative FRs for achieving commercial product fire safety standards are being developed and used. Some of these non-BDE BFRs are pentabromoethylbenzene (PBEB), hexabromobenzene (HBB), and decabromodiphenylethane (DBDPE) [28], 

HBCD is a brominated aliphatic cyclic hydrocarbon used as a flame retardant in thermal insulation building materials, upholstery textiles, and electronics. In 2001, the world market demand for HBCD was 16,700 tons, from which 9,500 tons was sold in the EU. These figures make HBCD the second highest volume BFR used in Europe [29], HBCD may be used as an alternative for PBDEs in some applications. To date, there are no restrictions on the production or use of HBCD. As a result of their widespread use and their physical and chemical properties, HBCD are now ubiquitous contaminants in the environment and humans [30, 31]. 

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Brominated Diphenyl Oxides. Brominated diphenyl oxides are prepared by the bromination of diphenyl oxide. They are often referred to as diphenyl ethers. Taken together, the class constitutes the largest volume of brominated flame retardants. They range ia properties from high melting sohds to hquids. They are used, as additives, ia virtually every polymer system. 

Decabrom has poor uv stabiUty ia styrenic resias and causes significant discoloration. The use of uv stabilizers can minimize, but not eliminate, this effect. For styrenic apphcations that require uv stabiUty, several other brominated flame retardants are more suitable. In polyolefins, the uv stabiUty of decabrom is more easily improved by the use of stabilizers. 

Octabromodiphenyl Oxide. Octabromodiphenyl oxide [32536-52-0] (OBDPO) is prepared by bromination of diphenyl oxide. The degree of bromination is controlled either through stoichiometry (34) or through control of the reaction kinetics (35). The melting poiat and the composition of the commercial products vary somewhat. OBDPO is used primarily ia ABS resias where it offers a good balance of physical properties. Poor uv stabiUty is the primary drawback and use ia ABS is being supplanted by other brominated flame retardants, primarily TBBPA. 

Ethylenebis(tetrabromophthalimide). The additive ethylenebis(tetrabromophthalimide) [41291 -34-3] is prepared from ethylenediamine and tetrabromophthabc anhydride [632-79-1]. It is a specialty product used ia a variety of appHcations. It is used ia engineering thermoplastics and polyolefins because of its thermal stabiUty and resistance to bloom (42). It is used ia styrenic resias because of its uv stabiUty (43). This flame retardant has been shown to be more effective on a contained bromine basis than other brominated flame retardants ia polyolefins (10). 

Bis(bexacbIorocycIopentadieno)cycIooctane. The di-Diels-Alder adduct of hexachlorocyclopentadiene [77 7 ] and cyclooctadiene (44) is a flame retardant having unusually good thermal stabiUty for a chlotinated aUphatic. In fact, this compound is comparable ia thermal stabiUty to brominated aromatics ia some appHcations. Bis(hexachlorocyclopentadieno)cyclooctane is usedia several polymers, especially polyamides (45) and polyolefins (46) for wire and cable appHcations. Its principal drawback is the relatively high use levels required compared to some brominated flame retardants. 

There are a relatively small number of producers of halogenated flame retardants, especially for brominated flame retardants, where three producers account for greater than 80% of world production. Table 10 gives estimates of the volumes of brominated and chlorinated flame retardants used worldwide. Volumes of flame retardants consumed in Japan have been summarized (61). Prices of halogenated flame retardants vary from less than 2.00/kg to as high as 13.00/kg. Cost to the user depends on the level of use of the specific flame retardant and other factors such as the use of stabilizers. 

The Brominated Flame Retardants Industry Panel (BFRIP) was formed ia 1985 within the Flame Retardant Chemicals Association (FRCA) to address such concerns about the use of decabromodiphenyl oxide. Siace 1990 the BFRIP has operated as a Chemical Self-Funded Technical Advocacy and Research (CHEMSTAR) panel within the Chemical Manufacturers Association (CMA) (64). As of 1993, members of BFRIP are Ak2o, Amerihaas (Dead Sea Bromine Group), Ethyl Corp., and Great Lakes Chemical. Siace its formation, BFRIP has presented updates to iadustry on a regular basis (65,66), and has pubhshed a summary of the available toxicity information on four of the largest volume brominated flame retardants (67,68) tetrabromo bisphenol A, pentabromodiphenyl oxide, octabromodiphenyl oxide, and decabromodiphenyl oxide. This information supplements that summarized ia Table 11. 

Research sponsored by BFRIP regarding the use of brominated flame retardants shows that there is no evidence that the use of decabromodiphenyl oxide leads to any unusual risk. In addition, a study by the National Bureau of Standards (now National Institute of Science and Technology) showed that the use of flame retardants significantly decreased the ha2ards associated with burning of common materials under reaUstic fire conditions (73). Work ia Japan confirms this finding (74). 

Phosphorus -bromine flame retardant synergy was demonstrated in a 2/1 polycarbonate/polyethylene blend. These data also show phosphorus to be about ten times more effective than bromine in this blend. Brominated phosphates, where both bromine and phosphorus are in the same molecule, were also studied. In at least one case, synergy is further enhanced when both phosphorus and bromine are in the same molecule as compared with a physical blend of a phosphorus and a bromine compound. On a weight basis, phosphorus and bromine in the same molecule are perhaps the most efficient flame retardant combination. The effect of adding an impact modifier was also shown. 

Table 1. Oxygen Index of PET Fibers Containing Phosphorus or Bromine Flame Retardants ...

Table 2. Enhancement of Bromine Flame Retardancy by Antimony and Phosphorus in a PET Fiberl... 

Incineration of a collection of polymers with 10 different kinds of brominated flame retardants has been studied under standardized laboratory conditions using varying parameters including temperature and air flow. Polybrominated diphenyl ethers like the deca-, octa-, and pentabromo compounds yield a mixture of brominated dibenzofurans while burning in polymeric matrices. Besides cyclization, debromination/hydrogenation is observed. Influence of matrix effects and burning conditions on product pattern has been studied the relevant mechanisms have been proposed and the toxicological relevance is discussed. 

M. Freiberg, D.L. McAllister, C.J. Mazac, P. Ranken Analysis of Trace Levels of Polybrominated Dibenzo-p-dioxins and Dibenzofurans in Brominated Flame Retardants Presented on June 30, 1993 at Orgabrom 93 in Jerusalem. 

See report of European Brominated Flame Retardant Industry Panel, March 1992, Bruxelles. 

The use of aromatic brominated compounds as flame retardants has been a potential source of environmental contamination. Incomplete incineration of these compounds and wastes (plastics, textiles, oils etc...) containing brominated flame retardants caused formation of brominated/chlorinated dibenzodioxines (PBDDs/ PCDDs) and dibenzofurans (PCDFs/PBDFs) (refs. 1 - 4). 

Algal and cyanobacterial toxins Brominated flame retardants Disinfection by-products Gasoline additives... 

Canton, R.F., Sanderson, J.T., and Nijmeijer, S. et al. (2006). In vitro effects of brominated flame retardants and metabolites on CYP17 catalytic activity A novel mechanism of action Toxicology and Applied Pharmacology 216, 274—281. 

Hewlett-Packard Development Company, L.P. (2005) HP to Ehminate Brominated Flame Retardants from External Case Parts of AH New HP Brand Products. [Online - cited 24 April 2007] Available from URL http //www.hp.eom/hpinfo/newsroom/press/2005/051101a.html... 

Data on additive production are mostly absent in LCI databases. Some data are available for metals production and for bisphenol-A, but even for widely used additives such as phthalates and brominated flame retardants, production data are not available. 

Covaci A, Harrad S, Abdallah MAE, Ali N, Law RJ, Herzke D, de Wit CA (2011) Novel brominated flame retardants a review of their analysis, environmental fate and behaviour. 

In addition, the concern about e-waste not only focuses on its vast quantity generated daily, but also more on the need to handle the toxic chemicals embedded in it. It is well known that e-waste contains lead, beryllium, mercury, cadmium (Cd), and brominated flame retardants (BFRs) among other chemical materials [3]. Furthermore, highly toxic chemicals such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and polybrominated dibenzo-p-dioxins and dibenzo-furans (PBDD/Fs) can be formed during the recycling process [4]. 

Shi T, Chen SJ, Luo XJ, Zhang XL, Tang CM, Luo Y, Ma YJ, Wu JP, Peng XZ, Mai BX (2009) Occurrence of brominated flame retardants other than polybrominated diphenyl ethers in environmental and biota samples from southern China Chemosphere 74(7) 910-916. doi 10.1016/j. chemosphere.2008.10.047... 

Choi K-I, Lee S-H, Osako M (2009) Leaching of brominated flame retardants from TV housing plastics in the presence of dissolved humic matter. Chemosphere 74(3) 460-466. doi 10.1016/j. chemosphere.2008.08.030... 

Keywords Brominated flame retardants, E-waste, Substance Flow Analysis SFA, Informal Recycling, Waste Electric and Electronic Equipment WEEE... 

Tasaki T, Takasuga T, Osako M, Sakai S-i (2004) Substance flow analysis of brominated flame retardants and related compounds in waste TV sets in Japan. Waste Manag 24(6) 571-580... 

The importance of assessing human and environmental impacts caused by emissions of metals and brominated flame retardants (BFRs) has been growing in... 

DEPA (Danish Environmental Protection Agency) 1999 Brominated flame retardants, Project No. 494... 

PBDEs are a class of brominated flame retardants (BFRs) used in textiles, plastics and electronic products. The effects of BFRs are associated with three commercial mixtures of PBDEs decaBDE, octaBDE and pentaBDE. In laboratory animal experiments, the toxicity of PBDEs was linked to damage to liver function and,... 

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