Brominated flame retardant
Brominated flame retardants (BFRs) are organobromide compounds that have an inhibitory effect on the ignition of combustible organic materials. Of the commercialized chemical flame retardants, the brominated variety are most widely used. They are very effective in plastics and textile applications, e.g. electronics, clothes and furniture. BFRs are commonly used in electronic products as a means of reducing the flammability of the product.
Types of compounds
- Polybrominated diphenyl ethers (PBDEs): DecaBDE, OctaBDE (not manufactured anymore), PentaBDE (not manufactured anymore, the first BFR, commercialized in the 1950s)
- Polybrominated biphenyl (PBB), not manufactured anymore
- Brominated cyclohydrocarbons
- Other brominated flame retardants with different properties and mechanisms
Decabromodiphenyl ether (Deca-BDE or DeBDE) - In August 2012, the UK authorities proposed decabromodiphenyl ether (Deca-BDE or DeBDE) as a candidate for Authorisation under the EU‘s regulatory regime on chemicals, REACH. On 5 July 2013 ECHA withdrew Deca-BDE from its list of priority substances for Authorisation under REACH, therefore closing the public consultation. On 1 August 2014, ECHA submitted a restriction proposal for Deca-BDE. The agency is proposing a restriction on the manufacture, use and placing on the market of the substance and of mixtures and articles containing it. On 17 September 2014, ECHA submitted the restriction report which initiates a six months public consultation. A decision could be adopted by mid-2016.
Hexabromocyclododecane (HBCD or HBCDD) is a ring consisting of twelve carbon atoms with six bromine atoms tied to the ring. The commercially used HBCD is in fact a mixture of different isomers. HBCD is toxic to water-living organisms. The UNEP Stockholm Convention has listed HBCD for elimination, but allowing a temporary exemption for the use in polystyrene insulation foams in buildings.
Tetrabromobisphenol A (TBBPA or TBBP-A) is regarded as toxic to water environment. This flame retardant is mainly used in printed circuit boards, as a reactive. Since TBBPA is chemically bound to the resin of the printed circuit board, it is less easily released than the loosely applied mixtures in foams such that an EU risk assessment concluded in 2005 that TBBPA poses no risk to human health in that application. TBBPA is also used as an additive in acrylonitrile butadiene styrene (ABS).
Contents in plastics
Content of brominated flame retardants in different polymers:
|High impact polystyrene||11–15||DecaBDE, brominated polystyrene|
|Polyamides||13–16||DecaBDE, brominated polystyrene|
|Polyolefins||5–8||DecaBDE, propylene dibromo styrene|
|Polyurethanes||n/a||No brominated FR available|
|Styrene copolymers||12–15||Brominated polystyrene|
390,000 tons of brominated flame retardants were sold in 2011. This represents 19.7% of the flame retardants market.
Types of applications
The electronics industry accounts for the greatest consumption of BFRs. In computers, BFRs are used in four main applications: in printed circuit boards, in components such as connectors, in plastic covers, and in cables. BFRs are also used in a multitude of products, including, but not exclusively, plastic covers of television sets, carpets, pillows, paints, upholstery, and domestic kitchen appliances.
Testing for BFR in plastics
Until recently testing for BFR has been cumbersome. Cycle time, cost and level of expertise required for the test engineer has precluded the implementation of any screening of plastic components in a manufacturing or in a product qualification/validation environment.
Recently, with the introduction of a new analytical instrument IA-Mass, screening of plastic material alongside a manufacturing line became possible. A five minute detection cycle and a 20 minute quantification cycle is available to test and to qualify plastic parts as they reach the assembly line. IA-Mass identifies the presence of bromine (PBB, PBDE, and some others), but cannot characterize all the BFRs present in the plastic matrix.
In February 2009, the Institute for Reference Materials and Measurements (IRMM) released two certified reference materials (CRMs) to help analytical laboratories better detect two classes of flame retardants, namely polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs). The two reference materials were custom made to contain all relevant PBDEs and PBBs at levels close to the legal limit set out in the RoHS Directive of 1 g/kg for the sum of PBBs and PBDEs.
Environmental and safety issues
Many brominated chemicals are under increasing criticism in their use in household furnishings and where children would come into contact with them. Some believe PBDEs could have harmful effects on humans and animals. Increasing concern has prompted some European countries to ban some of them, following the precautionary principle more common in Europe. Some PBDEs are lipophilic and bioaccumulative. PBDEs have been found in people all over the world.
Some brominated flame retardants were identified as persistent, bioaccumulative, and toxic to both humans and the environment and were suspected of causing neurobehavioral effects and endocrine disruption. As an example, in Europe, brominated flame retardants have gone through REACH and when risks were identified appropriate risk management options were put in place; such was the case for commercial Penta-BDE and commercial Octa-BDE. Given the current state of waste disposal in the world, there is a potential for BFRs to be released into the environment.
- Michael J. Dagani, Henry J. Barda, Theodore J. Benya, David C. Sanders “Bromine Compounds” Ullmann's Encyclopedia of Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a04_405
- The final decision is available on the UNEP Stockholm Convention website here: http://chm.pops.int/Convention/ConferenceoftheParties(COP)/Decisions/tabid/208/Default.aspx
- EU Risk Assessment Report (2006) http://www.bsef.com/uploads/library/final_tbbpa_human_health_report.pdf
- Pedro Arias (2001): Brominated flame retardants – an overview. The Second International Workshop on Brominated Flame Retardants, Stockholm
- Townsend Solutions Estimate, http://www.flameretardants-online.com/web/en/106/7ae3d32234954e28e661e506e284da7f.htm
- Stiffler, Lisa (March 28, 2007). "PBDEs: They are everywhere, they accumulate and they spread". Seattle Post Intelligencer.
- Kim Hooper ,Jianwen She (2003). "Lessons from the Polybrominated Diphenyl Ethers (PBDEs): Precautionary Principle, Primary Prevention, and the Value of Community-Based Body-Burden Monitoring Using Breast Milk". Environmental Health Perspectives 111 (1).
- European Union Risk Assessment Report of diphenyl ether, pentabromo deriv., 2000 http://echa.europa.eu/documents/10162/781ee1e9-6c90-467e-998b-8910ca2793e5
- European Union Risk Assessment Report of diphenyl ether, octabromo deriv., 2003 http://echa.europa.eu/documents/10162/5b10aa46-9a88-4aed-b338-1e06105b924c
- Kyle D'Silva, Alwyn Fernandes and Martin Rose (2004). "Brominated Organic Micropollutants—Igniting the Flame Retardant Issue". Critical Reviews in Environmental Science and Technology 34 (2): 141–207. doi:10.1080/10643380490430672.
- Law, Robin J.; Kohler, Martin; Heeb, Norbert V.; Gerecke, Andreas C.; Schmid, Peter; Voorspoels, Stefan; Covaci, Adrian; Becher, Georg; Janak, Karel (2005). "Hexabromocyclododecane Challenges Scientists and Regulators". Environmental Science & Technology 39 (13): 281A. doi:10.1021/es053302f.
- Cynthia A. de Wit (2002). "An overview of brominated flame retardants in the environment". Chemosphere 46 (5): 583–624. doi:10.1016/S0045-6535(01)00225-9. PMID 11999784.
- Young Ran Kim et al. (2014). "Health consequences of exposure to brominated flame retardants: A systematic review". Chemosphere 106: 1–19. doi:10.1016/j.chemosphere.2013.12.064.