Brominated flame-retardant
Encyclopedia
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.
s, in components such as connector
s, in plastic covers, and in cable
s. BFRs are also used in a multitude of products, including, but not exclusively, plastic covers of television sets, carpets, paints, upholstery, and domestic kitchen appliances.
in 70 variants with very varying chemical properties. There are several groups:
Decabromodiphenyl ether
(Deca-BDE or DeBDE) is regarded as a not-dangerous substance (no risk-phrase awarded under EU regulation 67/769).
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 isomer
s. HBCD is toxic to water-living organism
s. Studies carried out on a HBCD product that is no longer manufactured indicate that Humans can develop allergy
at skin contact. This is not the case anymore with the current HBCD-based products.
Tetrabromobisphenol A
(TBBPA or TBBP-A) is regarded as toxic to water environment. This flame retardant is mainly used in printed circuit board
s, 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.. However given the current state of waste disposal in the world, the BFRs are released into the environment and bioaccumulate. TBBPA is also used as an additive in acrylonitrile butadiene styrene
(ABS).
Recently, with the introduction of a new analytical instrument IA-Mass, screening of plastic material alongside manufacturing line becomes possible. A 5 min. detection cycle and a 20 min. 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.
more common in Europe. They are lipophilic and bioaccumulative. BFRs have been found in people all over the world.
Production
Bromine based flame retardants are applied to 2.5 million tons of polymers annually, with the annual consumption of PBDEs being in excess of 40,000 metric tons. North American industry used about 34,000 metric tons of PBDEs in 1999, making it the largest user of these additives globally; however, a significant proportion of the flame-retarded products manufactured in North America is destined for international markets.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 boardPrinted circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
s, in components such as connector
Electrical connector
An electrical connector is an electro-mechanical device for joining electrical circuits as an interface using a mechanical assembly. The connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or...
s, in plastic covers, and in cable
Cable
A cable is two or more wires running side by side and bonded, twisted or braided together to form a single assembly. In mechanics cables, otherwise known as wire ropes, are used for lifting, hauling and towing or conveying force through tension. In electrical engineering cables are used to carry...
s. BFRs are also used in a multitude of products, including, but not exclusively, plastic covers of television sets, carpets, paints, upholstery, and domestic kitchen appliances.
Types of compounds
They are produced syntheticallyOrganic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
in 70 variants with very varying chemical properties. There are several groups:
- Polybrominated diphenyl ethers (PBDEs): DecaBDE, OctaBDE (not manufactured anymore), PentaBDE (not manufactured anymore, the first BFR, commercialized in the 1950s)
- Polybrominated biphenylPolybrominated biphenylPolybrominated biphenyls , also called brominated biphenyls or polybromobiphenyls, are a group of manufactured chemicals, of the polyhalogenated compounds. Their chlorine analogs are the PCBs...
(PBB), not manufactured anymore - Brominated cyclohydrocarbons
Decabromodiphenyl ether
Decabromodiphenyl ether
Decabromodiphenyl ether is a brominated flame retardant which belongs to the group of polybrominated diphenyl ethers ....
(Deca-BDE or DeBDE) is regarded as a not-dangerous substance (no risk-phrase awarded under EU regulation 67/769).
Hexabromocyclododecane
Hexabromocyclododecane
Hexabromocyclododecane is a brominated flame retardant. It consists of twelve carbon, eighteen hydrogen, and six bromine atoms tied to the ring. Its primary application is in extruded and expanded polystyrene foam that is used as thermal insulation in the building industry...
(HBCD or HBCDD) is a ring consisting of twelve carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
atoms with six bromine
Bromine
Bromine ") is a chemical element with the symbol Br, an atomic number of 35, and an atomic mass of 79.904. It is in the halogen element group. The element was isolated independently by two chemists, Carl Jacob Löwig and Antoine Jerome Balard, in 1825–1826...
atoms tied to the ring. The commercially used HBCD is in fact a mixture of different isomer
Isomer
In chemistry, isomers are compounds with the same molecular formula but different structural formulas. Isomers do not necessarily share similar properties, unless they also have the same functional groups. There are many different classes of isomers, like stereoisomers, enantiomers, geometrical...
s. HBCD is toxic to water-living organism
Organism
In biology, an organism is any contiguous living system . In at least some form, all organisms are capable of response to stimuli, reproduction, growth and development, and maintenance of homoeostasis as a stable whole.An organism may either be unicellular or, as in the case of humans, comprise...
s. Studies carried out on a HBCD product that is no longer manufactured indicate that Humans can develop allergy
Allergy
An Allergy is a hypersensitivity disorder of the immune system. Allergic reactions occur when a person's immune system reacts to normally harmless substances in the environment. A substance that causes a reaction is called an allergen. These reactions are acquired, predictable, and rapid...
at skin contact. This is not the case anymore with the current HBCD-based products.
Tetrabromobisphenol A
Tetrabromobisphenol A
Tetrabromobisphenol A is a brominated flame retardant.- Synthesis :TBBPA is a derivative of bisphenol A and is synthesized from this substance. Most commercial TBBPA products are of a relatively low purity, in fact containing a mixture of products brominated to varying extents. This is not...
(TBBPA or TBBP-A) is regarded as toxic to water environment. This flame retardant is mainly used in printed circuit board
Printed circuit board
A printed circuit board, or PCB, is used to mechanically support and electrically connect electronic components using conductive pathways, tracks or signal traces etched from copper sheets laminated onto a non-conductive substrate. It is also referred to as printed wiring board or etched wiring...
s, 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.. However given the current state of waste disposal in the world, the BFRs are released into the environment and bioaccumulate. TBBPA is also used as an additive in acrylonitrile butadiene styrene
Acrylonitrile butadiene styrene
Acrylonitrile butadiene styrene is a common thermoplastic. Its melting point is approximately 105 °C ....
(ABS).
Contents in plastics
Content of brominated flame retardants in different polymers:| Polymer | Content [%] | Substances |
|---|---|---|
| Polystyrene Polystyrene Polystyrene ) also known as Thermocole, abbreviated following ISO Standard PS, is an aromatic polymer made from the monomer styrene, a liquid hydrocarbon that is manufactured from petroleum by the chemical industry... foam |
0,8–4 | HBCD |
| High impact polystyrene | 11–15 | DecaBDE, brominated polystyrene |
| Epoxy resin | 0-0,1 | TBBPA |
| Polyamide Polyamide A polyamide is a polymer containing monomers of amides joined by peptide bonds. They can occur both naturally and artificially, examples being proteins, such as wool and silk, and can be made artificially through step-growth polymerization or solid-phase synthesis, examples being nylons, aramids,... s |
13–16 | DecaBDE, brominated polystyrene |
| Polyolefin Polyolefin A polyolefin is a polymer produced from a simple olefin as a monomer. For example, polyethylene is the polyolefin produced by polymerizing the olefin ethylene. An equivalent term is polyalkene; this is a more modern term, although polyolefin is still used in the petrochemical industry... s |
5–8 | DecaBDE, propylene dibromo styrene |
| Polyurethane Polyurethane A polyurethane is any polymer composed of a chain of organic units joined by carbamate links. Polyurethane polymers are formed through step-growth polymerization, by reacting a monomer with another monomer in the presence of a catalyst.Polyurethanes are... s |
n/a | No brominated FR available |
| Polyterephthalate | 8–11 | Brominated polystyrene |
| Unsaturated polyester Polyester Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate... s |
13–28 | TBBPA |
| Polycarbonate Polycarbonate PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%... |
4–6 | Brominated polystyrene |
| Styrene copolymers | 12–15 | Brominated polystyrene |
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 component 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 manufacturing line becomes possible. A 5 min. detection cycle and a 20 min. 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)
Institute for Reference Materials and Measurements
The Institute for Reference Materials and Measurements , located in Geel, Belgium, is one of the seven institutes of the Joint Research Centre , a Directorate-General of the European Commission ....
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 coming under increasing criticism in their use in household furnishings and where children would come into contact with them. Some believe the chemicals, including PBDE could have harmful effects on humans and animals. Increasing concern has prompted some European countries to ban some of them, following the precautionary principlePrecautionary principle
The precautionary principle or precautionary approach states that if an action or policy has a suspected risk of causing harm to the public or to the environment, in the absence of scientific consensus that the action or policy is harmful, the burden of proof that it is not harmful falls on those...
more common in Europe. They are lipophilic and bioaccumulative. BFRs have been found in people all over the world.