Flame retardant
Encyclopedia
Flame retardants are chemicals used in thermoplastics, thermosets, textiles and coatings that inhibit or resist the spread of fire. These can be separated into several different classes of chemicals:
Mineral flame retardants are typically additive while organohalogen and organophosphorus can be either reactive or additive. The basic mechanisms of flame retardancy vary depending on the specific flame retardant and the substrate. Additive and reactive flame-retardant chemicals can function in the vapor or condensed phase.
The annual consumption of flame retardants is currently over 1.5 million tonnes per year, which is the equivalent of a sales volume of approx. 1.9 billion Euro (2.4 billion US-$).
s such as hydromagnesite
. The reaction removes heat from the substrate, thereby cooling the material. The use of hydroxides and hydrates is limited by their relatively low decomposition temperature, which limits the maximum processing temperature of the polymers (typically used in polyolefins for wire and cable applications).
additives are often employed; their role is to turn the polymer into a char, which separates the flame from the material and slows the heat transfer to the unburned fuel.
and water
) produced by thermal degradation of some materials act as diluents of the combustible gases, lowering their partial pressures and the partial pressure of oxygen, and slowing the reaction rate.
and hydrogen bromide
or if used in the presence of a synergist like antimony trioxide antimony halides. These react with the highly reactive H· and OH· radicals
in the flame, resulting in an inactive molecule and a Cl· or Br· radical. The halogen radical has much lower energy than H· or OH·, and therefore has much lower potential to propagate the radical oxidation reactions of combustion.
As of 2008 the United States, Europe and Asia have a annual consumption rate for flame retardants at 1.8 million metric tons and valued at $4.20-4.25 billion dollars. According to the Ceresana Research, the market for flame retardants is increasing due to rising safety standards worldwide and the increase use of flame retardants. It is forecasted that the global flame retardant market will generate $5.8 billion dollars (US). As of 2010, the Asia-Pacific region was the largest market for flame retardants which was approximately 41% of global demand followed by North America, and Western Europe.
released a report on polybrominated diphenyl ethers (PBDEs) and found that, in contrast to earlier reports, they were found throughout the U.S. coastal zone. This nationwide survey found that New York’s Hudson Raritan Estuary had the highest overall concentrations of PBDEs, both in sediments and shellfish. Individual sites with the highest PBDE measurements were found in shellfish taken from Anaheim Bay, California, and four sites in the Hudson Raritan Estuary. Watersheds that include the Southern California Bight, Puget Sound, the central and eastern Gulf of Mexico off the Tampa-St. Petersburg, Fla. coast, and Lake Michigan waters near Chicago and Gary, Ind. also were found to have high PBDE concentrations.
Firefighters who responded to the World Trade Center Attacks on 11 September 2011 are out a higher chance for having lung problems. Due to the fact the World Trade Center was built in the 1970’s and parts of the building construction contain asbestos materials. The first few days after the attack level of asbestos in the air where at evaluated rates and firefighter working in the area were not wearing proper PPE for the environment.
Nearly all Americans tested have trace levels of flame retardants in their body. Recent research links some of this exposure to dust on television sets, which may have been generated from the heating of of the flame retardants in the TV. Careless disposal of TVs and other appliances such as microwaves or old computers may greatly increase the amount of environmental contamination.
A recent study conducted by Harley et al. 2010 on pregnant women, living in a low-income, predominantly Mexican-immigrant community in California showed a significant decrease in fecundity associated with PBDE exposure in women.
Another study conducted by Chevrier et al. 2010 measured the concentration of 10 PBDE congeners, free thyroxine (T4), total T4, and thyroid-stimulating hormone (TSH) in 270 pregnant women around the 27th week of gestation. Associations between PBDEs and free and total T4 were found to be statistically insignificant. However, authors did find a significant association amongst exposure to PBDEs and lower TSH during pregnancy, which may have implications for maternal health and fetal development.
A prospective, longitudinal cohort study initiated after 11 September 2001, including 329 mothers who delivered in one of three hospitals in lower Manhattan, New York, was conducted by Herbstman et al. 2010. Authors of this study analyzed 210 cord blood specimens for selected PBDE congeners and assessed neurodevelopmental effects in the children at 12–48 and 72 months of age. Results showed that children who had higher cord blood concentrations of polybrominated diphenyl ethers (PBDEs) scored lower on tests of mental and motor development at 1–4 and 6 years of age. This was the first study to report any such associations in humans.
A similar study was conducted by Roze et al. 2009 in Netherlands on 62 mothers and children to estimate associations between 12 Organohalogen compounds (OHCs), including polychlorinated biphenyls (PCBs) and brominated diphenyl ether (PBDE) flame retardants, measured in maternal serum during the 35th week of pregnancy and motor performance (coordination, fine motor skills), cognition (intelligence, visual perception, visuomotor integration, inhibitory control, verbal memory, and attention), and behavior scores at 5–6 years of age. Authors demonstrated for the first time that transplacental transfer of polybrominated flame retardants was associated with the development of children at school age.
Another interesting study was conducted by Rose et al. 2010 to measure circulating PBDE levels in 100 children between 2 to 5 years of age from California. The PBDE levels according to this study, in 2- to 5-year-old California children was 10 to 1,000 fold higher than European children, 5 times higher than other U.S. children and 2 to 10 times higher than U.S. adults. They also found that diet, indoor environment, and social factors influenced children’s body burden levels. Eating poultry and pork contributed to elevated body burdens for nearly all types of flame retardants. Study also found that lower maternal education was independently and significantly associated with higher levels of most flame retardant congeners in the children.
San Antonio Statement on Brominated and Chlorinated Flame Retardants 2010: A group of 145 prominent scientists from 22 countries signed the first-ever consensus statement documenting health hazards from flame retardant chemicals found at high levels in home furniture
, electronics
, insulation
, and other products. This statement documents that, with limited fire safety benefit, these flame retardants can cause serious health issues, and, as types of flame retardants are banned, the alternatives should be proven safe before being used. The group also wants to change widespread policies that require use of flame retardants.
A number of recent studies suggest that dietary intake is one of the main routes to human exposure to PBDEs. In recent years, PBDEs have become widespread environmental pollutants, while body burden in the general population has been increasing. The results do show notable coincidences between the China, Europe, Japan, and United States such as dairy products, fish, and seafood being a cause of human exposure to PBDEs due to the environmental pollutant.
This checklist is cited from the Department of Health in Washington state.
• Cleaning - PBDEs in indoor dust is one of the primary sources of people's exposure. Reduce your exposure to indoor dust. Use a damp cloth to dust indoor living and working areas. Avoid stirring the dust into the air. Use a vacuum with a HEPA filter. Open windows and doors while you clean. Wash hands after dusting and cleaning.
• Foam products - New foam items that you purchase today are unlikely to contain PBDEs. However, mattresses, mattress pads, couches, easy chairs, foam pillows, carpet padding, and other foam products purchased before 2005 likely contain PBDEs. Replace older foam products that have ripped covers or foam that is misshapen or breaking down. If you can't replace the item, try to keep the covers intact. When removing old carpet foam, keep the work area sealed from other areas of the house, avoid breathing in the dust, and use a HEPA-filter vacuum for cleanup.
• Electronics - Deca-BDE has been used in electronics for years but is now being phased out of most electronics. When purchasing electronics, request products that contain no Deca-BDE or other bromine-containing fire retardants.
• Foods - PBDEs can concentrate in the fat of poultry, red meat, fish and other fatty meats. See how to reduce the fat when preparing and cooking fish (these tips can be applied to other meats). Wash hands before preparing and eating food.
• Disposal and recycling - PBDEs will continue to pollute the environment unless flame retardant products are disposed of properly. To keep PBDEs out of the environment, dispose of foam containing products and electronics such as TVs and computers at your nearest hazardous waste collection site.
in 1994. A 1998 UK government-sponsored study called the Limerick Report found that toxic gases were not created. Based on the Limerick report, position papers publicized by US SIDS organizations say there is not enough evidence to support the toxic gas theory, and that parents should continue to put their babies to sleep on vinyl-covered crib mattresses. However, Sprott maintains that his findings were not refuted.
- Minerals such as aluminium hydroxideAluminium hydroxideAluminium hydroxide, Al3, ATH, sometimes erroneously called Hydrate of alumina, is found in nature as the mineral gibbsite and its three, much more rare forms, polymorphs: bayerite, doyleite and nordstrandite. Closely related are aluminium oxide hydroxide, AlO, and aluminium oxide, Al2O3,...
ATH, magnesium hydroxideMagnesium hydroxideMagnesium hydroxide is an inorganic compound with the chemical formula Mg2. As a suspension in water, it is often called milk of magnesia because of its milk-like appearance. The solid mineral form of magnesium hydroxide is known as brucite....
MDH, hydromagnesiteHydromagnesiteHydromagnesite is a hydrated magnesium carbonate mineral with the formula: Mg542.4H2O.It generally occurs associated with the weathering products of magnesium containing minerals such as serpentine or brucite. It occurs as incrustations and vein or fracture fillings in ultramafic rocks and...
, various hydrateHydrateHydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
s, red phosphorus, and boronBoronBoron is the chemical element with atomic number 5 and the chemical symbol B. Boron is a metalloid. Because boron is not produced by stellar nucleosynthesis, it is a low-abundance element in both the solar system and the Earth's crust. However, boron is concentrated on Earth by the...
compounds, mostly borateBorateBorates are chemical compounds which contain oxoanions of boron in oxidation state +3. The simplest borate ion, BO33−, has a trigonal planar structure. Other borates are made up of trigonal BO3 or tetrahedral BO4 structural units, sharing oxygen atoms...
s. - Organohalogen Compounds. These include organochlorines such as, chlorendic acidChlorendic acidChlorendic acid, or 1,4,5,6,7,7-hexachlorobicyclo[2.2.1]-hept-5-ene-2,3-dicarboxylic acid, is a chlorinated hydrocarbon used in the synthesis of some flame retardants and polymers. It is a common breakdown product of several organochlorine insecticides....
derivatives and chlorinatedHalogenationHalogenation is a chemical reaction that incorporates a halogen atom into a molecule in substitution of hydrogen atom. Halogenation takes place in the gas phase. There are four types of halogenation: fluorination, chlorination, bromination, and iodination...
paraffinParaffinIn chemistry, paraffin is a term that can be used synonymously with "alkane", indicating hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to a mixture of alkanes that falls within the 20 ≤ n ≤ 40 range; they are found in the solid state at room temperature and begin to enter the...
s; organobromines such as decabromodiphenyl etherDecabromodiphenyl etherDecabromodiphenyl ether is a brominated flame retardant which belongs to the group of polybrominated diphenyl ethers ....
(decaBDE), decabromodiphenyl ethane (a replacement for decaBDE), polymeric brominated compounds such as brominated polystyrenes, brominated carbonate oligomers (BCOs), brominated epoxy oligomers (BEOs), tetrabromophthalic anyhydride, tetrabromobisphenol ATetrabromobisphenol ATetrabromobisphenol 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) and hexabromocyclododecaneHexabromocyclododecaneHexabromocyclododecane 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). Most but not all halogenated flame retardants are used in conjunction with a synergist to enhance their efficiency. Antimony trioxide is widely used but other forms of antimony such as the pentoxide and sodium antimonate are also used. - Organophosphorus compounds such as organophosphateOrganophosphateAn organophosphate is the general name for esters of phosphoric acid. Phosphates are probably the most pervasive organophosphorus compounds. Many of the most important biochemicals are organophosphates, including DNA and RNA as well as many cofactors that are essential for life...
s, tris(2,3-dibromopropyl) phosphateTris(2,3-dibromopropyl) phosphateTris phosphate is a chemical once widely used as a flame retardant in plastics and textiles.-Safety and regulation:...
, TPP, RDP, BPADP, tri-o-cresyl phosphateTricresyl phosphateTricresyl phosphate, abbreviated TCP, is an organophosphate compound that is used as a plasticizer and diverse other applications. It is a colourless, viscous liquid, although commercial samples are typically yellow...
, phosphonates such as DMMP and phosphinates. There is also an important class of flame retardants that contain both phosphorus and halogen, examples of such are the chlorophosphates like TMCP and TDCP.
Mineral flame retardants are typically additive while organohalogen and organophosphorus can be either reactive or additive. The basic mechanisms of flame retardancy vary depending on the specific flame retardant and the substrate. Additive and reactive flame-retardant chemicals can function in the vapor or condensed phase.
The annual consumption of flame retardants is currently over 1.5 million tonnes per year, which is the equivalent of a sales volume of approx. 1.9 billion Euro (2.4 billion US-$).
Endothermic degradation
Some compounds break down endothermically when subjected to high temperatures. Magnesium and aluminium hydroxides are an example, together with various hydrateHydrate
Hydrate is a term used in inorganic chemistry and organic chemistry to indicate that a substance contains water. The chemical state of the water varies widely between hydrates, some of which were so labeled before their chemical structure was understood....
s such as hydromagnesite
Hydromagnesite
Hydromagnesite is a hydrated magnesium carbonate mineral with the formula: Mg542.4H2O.It generally occurs associated with the weathering products of magnesium containing minerals such as serpentine or brucite. It occurs as incrustations and vein or fracture fillings in ultramafic rocks and...
. The reaction removes heat from the substrate, thereby cooling the material. The use of hydroxides and hydrates is limited by their relatively low decomposition temperature, which limits the maximum processing temperature of the polymers (typically used in polyolefins for wire and cable applications).
Thermal shielding
A way to stop spreading of the flame over the material is to create a thermal insulation barrier between the burning and unburned parts. IntumescentIntumescent
An intumescent is a substance which swells as a result of heat exposure, thus increasing in volume, and decreasing in density. Intumescents are typically used in passive fire protection and, in America, require listing and approval use and compliance in their installed configurations in order to...
additives are often employed; their role is to turn the polymer into a char, which separates the flame from the material and slows the heat transfer to the unburned fuel.
Dilution of gas phase
Inert gases (most often carbon dioxideCarbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
) produced by thermal degradation of some materials act as diluents of the combustible gases, lowering their partial pressures and the partial pressure of oxygen, and slowing the reaction rate.
Gas phase radical quenching
Chlorinated and brominated materials undergo thermal degradation and release hydrogen chlorideHydrogen chloride
The compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...
and hydrogen bromide
Hydrogen bromide
Hydrogen bromide is the diatomic molecule HBr. HBr is a gas at standard conditions. Hydrobromic acid forms upon dissolving HBr in water. Conversely, HBr can be liberated from hydrobromic acid solutions with the addition of a dehydration agent, but not by distillation. Hydrogen bromide and...
or if used in the presence of a synergist like antimony trioxide antimony halides. These react with the highly reactive H· and OH· radicals
Radical (chemistry)
Radicals are atoms, molecules, or ions with unpaired electrons on an open shell configuration. Free radicals may have positive, negative, or zero charge...
in the flame, resulting in an inactive molecule and a Cl· or Br· radical. The halogen radical has much lower energy than H· or OH·, and therefore has much lower potential to propagate the radical oxidation reactions of combustion.
As of 2008 the United States, Europe and Asia have a annual consumption rate for flame retardants at 1.8 million metric tons and valued at $4.20-4.25 billion dollars. According to the Ceresana Research, the market for flame retardants is increasing due to rising safety standards worldwide and the increase use of flame retardants. It is forecasted that the global flame retardant market will generate $5.8 billion dollars (US). As of 2010, the Asia-Pacific region was the largest market for flame retardants which was approximately 41% of global demand followed by North America, and Western Europe.
Environmental prevalence
In 2009, the U.S. National Oceanic and Atmospheric Administration (NOAA)National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...
released a report on polybrominated diphenyl ethers (PBDEs) and found that, in contrast to earlier reports, they were found throughout the U.S. coastal zone. This nationwide survey found that New York’s Hudson Raritan Estuary had the highest overall concentrations of PBDEs, both in sediments and shellfish. Individual sites with the highest PBDE measurements were found in shellfish taken from Anaheim Bay, California, and four sites in the Hudson Raritan Estuary. Watersheds that include the Southern California Bight, Puget Sound, the central and eastern Gulf of Mexico off the Tampa-St. Petersburg, Fla. coast, and Lake Michigan waters near Chicago and Gary, Ind. also were found to have high PBDE concentrations.
Health concerns
Flame retardants have faced renewed attention in recent years. The earliest flame retardants, polychlorinated biphenyls (PCBs) were banned in 1977 when it was discovered that they are toxic. Industries shifted to using brominated flame retardants instead, but these are now receiving closer scrutiny. The EU has banned several types of polybrominated diphenyl ethers (PBDEs) as of 2008, 10 years after Sweden discovered that they were accumulating in breast milk. As of December 2009, negotiations between EPA and the two U.S. producers of DecaBDE (a flame retardant that has been used in electronics, wire and cable insulation, textiles, automobiles and airplanes, and other applications), Albemarle Corporation and Chemtura Corporation, and the largest U.S. importer, ICL Industrial Products, Inc., resulted in commitments by these companies to phase out decaBDE for most uses in the United States by December 31, 2012, and to end all uses by the end of 2013.Firefighters who responded to the World Trade Center Attacks on 11 September 2011 are out a higher chance for having lung problems. Due to the fact the World Trade Center was built in the 1970’s and parts of the building construction contain asbestos materials. The first few days after the attack level of asbestos in the air where at evaluated rates and firefighter working in the area were not wearing proper PPE for the environment.
Nearly all Americans tested have trace levels of flame retardants in their body. Recent research links some of this exposure to dust on television sets, which may have been generated from the heating of of the flame retardants in the TV. Careless disposal of TVs and other appliances such as microwaves or old computers may greatly increase the amount of environmental contamination.
A recent study conducted by Harley et al. 2010 on pregnant women, living in a low-income, predominantly Mexican-immigrant community in California showed a significant decrease in fecundity associated with PBDE exposure in women.
Another study conducted by Chevrier et al. 2010 measured the concentration of 10 PBDE congeners, free thyroxine (T4), total T4, and thyroid-stimulating hormone (TSH) in 270 pregnant women around the 27th week of gestation. Associations between PBDEs and free and total T4 were found to be statistically insignificant. However, authors did find a significant association amongst exposure to PBDEs and lower TSH during pregnancy, which may have implications for maternal health and fetal development.
A prospective, longitudinal cohort study initiated after 11 September 2001, including 329 mothers who delivered in one of three hospitals in lower Manhattan, New York, was conducted by Herbstman et al. 2010. Authors of this study analyzed 210 cord blood specimens for selected PBDE congeners and assessed neurodevelopmental effects in the children at 12–48 and 72 months of age. Results showed that children who had higher cord blood concentrations of polybrominated diphenyl ethers (PBDEs) scored lower on tests of mental and motor development at 1–4 and 6 years of age. This was the first study to report any such associations in humans.
A similar study was conducted by Roze et al. 2009 in Netherlands on 62 mothers and children to estimate associations between 12 Organohalogen compounds (OHCs), including polychlorinated biphenyls (PCBs) and brominated diphenyl ether (PBDE) flame retardants, measured in maternal serum during the 35th week of pregnancy and motor performance (coordination, fine motor skills), cognition (intelligence, visual perception, visuomotor integration, inhibitory control, verbal memory, and attention), and behavior scores at 5–6 years of age. Authors demonstrated for the first time that transplacental transfer of polybrominated flame retardants was associated with the development of children at school age.
Another interesting study was conducted by Rose et al. 2010 to measure circulating PBDE levels in 100 children between 2 to 5 years of age from California. The PBDE levels according to this study, in 2- to 5-year-old California children was 10 to 1,000 fold higher than European children, 5 times higher than other U.S. children and 2 to 10 times higher than U.S. adults. They also found that diet, indoor environment, and social factors influenced children’s body burden levels. Eating poultry and pork contributed to elevated body burdens for nearly all types of flame retardants. Study also found that lower maternal education was independently and significantly associated with higher levels of most flame retardant congeners in the children.
San Antonio Statement on Brominated and Chlorinated Flame Retardants 2010: A group of 145 prominent scientists from 22 countries signed the first-ever consensus statement documenting health hazards from flame retardant chemicals found at high levels in home furniture
Couch
A couch, also called a sofa, is an item of furniture designed to seat more than one person, and providing support for the back and arms. Typically, it will have an armrest on either side. In homes couches are normally found in the family room, living room, den or the lounge...
, electronics
Electronics
Electronics is the branch of science, engineering and technology that deals with electrical circuits involving active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies...
, insulation
Insulation
Insulation means:* Building insulation, added to buildings for comfort and energy efficiency* Soundproofing, also known as acoustic insulation, any means of reducing the intensity of sound...
, and other products. This statement documents that, with limited fire safety benefit, these flame retardants can cause serious health issues, and, as types of flame retardants are banned, the alternatives should be proven safe before being used. The group also wants to change widespread policies that require use of flame retardants.
A number of recent studies suggest that dietary intake is one of the main routes to human exposure to PBDEs. In recent years, PBDEs have become widespread environmental pollutants, while body burden in the general population has been increasing. The results do show notable coincidences between the China, Europe, Japan, and United States such as dairy products, fish, and seafood being a cause of human exposure to PBDEs due to the environmental pollutant.
This checklist is cited from the Department of Health in Washington state.
• Cleaning - PBDEs in indoor dust is one of the primary sources of people's exposure. Reduce your exposure to indoor dust. Use a damp cloth to dust indoor living and working areas. Avoid stirring the dust into the air. Use a vacuum with a HEPA filter. Open windows and doors while you clean. Wash hands after dusting and cleaning.
• Foam products - New foam items that you purchase today are unlikely to contain PBDEs. However, mattresses, mattress pads, couches, easy chairs, foam pillows, carpet padding, and other foam products purchased before 2005 likely contain PBDEs. Replace older foam products that have ripped covers or foam that is misshapen or breaking down. If you can't replace the item, try to keep the covers intact. When removing old carpet foam, keep the work area sealed from other areas of the house, avoid breathing in the dust, and use a HEPA-filter vacuum for cleanup.
• Electronics - Deca-BDE has been used in electronics for years but is now being phased out of most electronics. When purchasing electronics, request products that contain no Deca-BDE or other bromine-containing fire retardants.
• Foods - PBDEs can concentrate in the fat of poultry, red meat, fish and other fatty meats. See how to reduce the fat when preparing and cooking fish (these tips can be applied to other meats). Wash hands before preparing and eating food.
• Disposal and recycling - PBDEs will continue to pollute the environment unless flame retardant products are disposed of properly. To keep PBDEs out of the environment, dispose of foam containing products and electronics such as TVs and computers at your nearest hazardous waste collection site.
Sudden infant death syndrome
UK scientist Barry Richardson claimed in 1989 that a fungus in bedding broke down the antimony, phosphorus, and arsenic flame retardants in infant bedding to form toxic gases. This research was taken up by New Zealand scientist Jim Sprott, who published a book on the topic, and eventually aired on The Cook ReportThe Cook Report
The Cook Report was a British current affairs television programme shown on ITV, produced for the network by Central Television from 1987 to 1998.-History:...
in 1994. A 1998 UK government-sponsored study called the Limerick Report found that toxic gases were not created. Based on the Limerick report, position papers publicized by US SIDS organizations say there is not enough evidence to support the toxic gas theory, and that parents should continue to put their babies to sleep on vinyl-covered crib mattresses. However, Sprott maintains that his findings were not refuted.