- Flame retardant
Flame retardants are materials that inhibit or resist the spread of
fire. These can be separated into several categories:
*Minerals such as
asbestos, compounds such as aluminium hydroxide, magnesium hydroxide, antimony trioxide, various hydrates, red phosphorus, and boroncompounds, mostly borates.
*Tetrakis(hydroxymethyl)phosphonium salts, made by passing
phosphinegas through a solution of formaldehydeand a mineral acidsuch as hydrochloric acid, are used as flame retardants for textiles.
*Synthetic materials, usually
halocarbons. These include organochlorinessuch as polychlorinated biphenyls (PCBs), chlorendic acidderivates (most often dibutyl chlorendate and dimethyl chlorendate) and chlorinated paraffins; organobromines such as polybrominated diphenyl ether(PBDEs), which be further broken down into pentabromodiphenyl ether(pentaBDE), octabromodiphenyl ether(octaBDE), decabromodiphenyl ether(decaBDE) and hexabromocyclododecane(HBCD); organophosphates in the form of halogenated phosphorus compounds such as tri-o-cresyl phosphate, tris(2,3-dibromopropyl) phosphate (TRIS), bis(2,3-dibromopropyl) phosphate, tris(1-aziridinyl)-phosphine oxide (TEPA), and others.
James Gillraycaricatured the hazard of muslinclothing not treated with a flame retardant.] Many of these chemicals are considered harmful, having been linked to liver, thyroid, reproductive/developmental, and neurological effects. [ [http://www.epa.state.il.us/reports/decabde-study/index.html Illinois EPA Report on Flame Retardant] ] PCBs were banned in 1977ATSDR. (2001). [http://www.atsdr.cdc.gov/tfacts17.html#bookmark01 ToxFAQ PCBs] .] and the EU has banned several types of brominated flame retardants as of 2008, [http://www.ehponline.org/members/2008/116-5/innovations.html New Thinking on Flame Retardants] , "Environmental Health Perspectives," 116(5), May 2008] following evidence beginning in 1998 that the chemicals were accumulating in human breast milk. [Y. Lind, P. O. Darnerud, S. Atuma, M. Aune, W. Becker, R. Bjerselius, S. Cnattingius and A. Glynn (2003). "Polybrominated diphenyl ethers in breast milk from Uppsala County, Sweden." Environmental Research 93(2): 186–194. PMID 12963403] Currently some US states and various countries are investigating PBDEs as well; of the major ones only decaBDE remains on the North American market.
Aside from various conventional alternatives such as antinomony or phosphorus-based retardants which have toxicological problems of their own, "
Environmental Health Perspectives" surveys the halogen-free alternatives being explored. These include a technique to fuse flame retardants into products (so no chemicals leak), nanoclays incorporating montmorillonite, an entirely new plastic which produces water when burned called bishydroxydeoxybenzoin(BHDB), [ [UMass Scientists Create New Plastic] ] and possibly other nanomaterial solutions. Inherently flame-resistant products are ideal, and the aerospace industry uses such plastics, but they are too costly for widespread use.
Mechanisms of function
Some compounds break down endothermically when subjected to high temperatures. Magnesium and aluminium hydroxides are an example, together with various
hydrates. The reaction removes heat from the surrounding, thus 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.
Dilution of fuel
Inert fillers, eg.
talcor calcium carbonate, act as diluents, lowering the combustible portion of the material, thus lowering the amount of heat per volume of material it can produce while burning.
A way to stop spreading of the flame over the material is to create a thermal insulation barrier between the burning and unburned parts.
Intumescentadditives are often employed; their role is to turn the polymer into a carbonized foam, 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 dioxideand 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.
Gas phase radical quenching
Chlorinated and brominated materials undergo thermal degradation and release
hydrogen chlorideand hydrogen bromide. 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. Antimonycompounds tend to act in synergy with halogenated flame retardants. The HCl and HBr released during burning are highly corrosive, which has reliability implications for objects (especially fine electronics) subjected to the released smoke.
Flame retardants have faced renewed attention in recent years. The earliest flame retardants,
polychlorinated biphenyls(PCBs) were banned in the 1977 when it was discovered that they were 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(PDBEs) as of 2008, 10 years after Sweden discovered that they were accumulating in breast milk. 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 TV heating up 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. [Seattle-Times. (2008) [http://seattletimes.nwsource.com/html/health/2004406134_dust11.html Harmful chemical wafts from your TV] . Retrieved Sunday, May 11, 2008.]
udden 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 it, and eventually aired on
The Cook Reportin 1994. A 1998 UK government-sponsored study called the Limerick Report found that toxic gases were not created. [ [http://news.bbc.co.uk/2/low/uk_news/97992.stm BBC. (1998). Mattresses 'not responsible' for cot deaths] ] Sprott maintains that his findings were not refuted. [ [http://www.cotlife2000.co.nz/limerick.htm Critique of the UK Limerick Report] ]
Brominated flame retardant
* [http://bsef.com The Bromine Science Environmental Forum]
* [http://www.fireretardant-forum.com The Fire Retardant Forum]
* [http://www.cefic-efra.com/content/Default.asp?PageID=116 Flame retardants FAQ document]
* [http://www.flameretardants.eu European Flame Retardants Association website]
Wikimedia Foundation. 2010.
Look at other dictionaries:
flame-retardant — flame re|tar|dant [ fleım rı,tardnt ] adjective flame retardant clothing or substances have been treated with chemicals that stop them from burning easily in a fire … Usage of the words and phrases in modern English
flame-retardant — flame′ retard ant adj. tex not subject to quick or easy burning esp. through chemical treatment: flame retardant curtains[/ex] • Etymology: 1945–50 … From formal English to slang
flame-retardant — 1. adjective Used to describe something that is hard to ignite; that does not support or convey flame. 2. noun A substance used to make an object flameproof. The flame retardant used on the childs pajamas would keep them from bursting into flame … Wiktionary
flame retardant — antipirenas statusas T sritis chemija apibrėžtis Medžiaga, didinanti organinės kilmės medžiagos atsparumą degimui. atitikmenys: angl. antipyrene; fire retardant; fire retarder; flame retardant; flame retarder; flammable inhibitor rus. антипирен;… … Chemijos terminų aiškinamasis žodynas
flame-retardant — ADJ Flame retardant is the same as fire retardant … English dictionary
flame-retardant — UK [ˈfleɪm rɪˌtɑː(r)d(ə)nt] / US [ˈfleɪm rɪˌtɑrd(ə)nt] adjective flame retardant clothing or substances have been treated with chemicals that stop them from burning easily in a fire … English dictionary
flame-retardant — flame re·tar·dant (flāmʹrĭ tär dnt) adj. Resistant to catching fire. flameʹ re·tar dant n. * * * … Universalium
flame retardant — noun A chemical used to impart flame resistance … Wiktionary
flame-retardant — adjective Date: 1947 made or treated so as to resist burning … New Collegiate Dictionary
flame retardant — a compound used in cloth and plastic material to raise the ignition point of the material, thus making it resistant to fire. [1945 50] * * * … Universalium