Fire-safe polymers are

polymers A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic an ...

that are resistant to

degradation Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradatio ...

at high temperatures. There is need for fire-resistant polymers in the construction of small, enclosed spaces such as skyscrapers, boats, and airplane cabins.Zhang, H. ''Fire-Safe Polymers and Polymer Composites,'' Federal Aviation Administration technical report; U.S. Department of Transportation: Washington, D.C., 2004. In these tight spaces, ability to escape in the event of a

fire Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. At a certain point in the combustion reaction, called the ignition point, flames a ...

is compromised, increasing

risk. In fact, some studies report that about 20% of victims of airplane crashes are killed not by the crash itself but by ensuing

fires Fire is the rapid oxidation of a material (the fuel) in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. At a certain point in the combustion reaction, called the ignition point, flames are pr ...

.Sarkos, C. P. The Effect of Cabin Materials on Aircraft Postcrash Fire Survivability. ''Technical Papers of the Annual Technical Conference'' 1996, ''54'' (3), 3068-3071. Fire-safe

also find application as

adhesives Adhesive, also known as glue, cement, mucilage, or paste, is any non-metallic substance applied to one or both surfaces of two separate items that binds them together and resists their separation. The use of adhesives offers certain advant ...

in aerospace materials,Kumar, D.; Gupta, A. D.; Khullar, M. Heat-resistant thermosetting polymers based on a novel tetrakisaminophenoxycyclotriphosphazene. ''J. Polym. Sci. Part A: Polym. Chem.'' 1993, ''31'' (11), 2739-2745

insulation Insulation may refer to: Thermal * Thermal insulation, use of materials to reduce rates of heat transfer ** List of insulation materials ** Building insulation, thermal insulation added to buildings for comfort and energy efficiency *** Insulated ...

for

electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons using electronic devices. Electronics uses active devices to control electron flow by amplification ...

, and in military materials such as canvas tenting.Hindersinn, R. R. Historical Aspects of Polymer Fire Retardance. In ''Fire and Polymers – Hazards Identification and Prevention;'' Nelson, G. L., Ed.; American Chemical Society: Washington, D.C., 1990; pp 87-96. Some fire-safe

naturally exhibit an intrinsic resistance to

decomposition Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is e ...

, while others are synthesized by incorporating fire-resistant additives and fillers. Current research in developing fire-safe

is focused on modifying various properties of the

such as ease of

ignition Ignition may refer to: Science and technology * Firelighting, the human act of creating a fire for warmth, cooking and other uses * Combustion, an exothermic chemical reaction between a fuel and an oxidant * Fusion ignition, the point at which a ...

, rate of heat release, and the evolution of smoke and toxic gases. Standard methods for testing

polymer A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic a ...

flammability A combustible material is something that can burn (i.e., ''combust'') in air. A combustible material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable mat ...

vary among countries; in the United States common fire tests include the UL 94 small-flame test, the ASTM E 84 Steiner Tunnel, and the ASTM E 622

National Institute of Standards and Technology The National Institute of Standards and Technology (NIST) is an agency of the United States Department of Commerce whose mission is to promote American innovation and industrial competitiveness. NIST's activities are organized into physical s ...

(NIST) smoke chamber. Research on developing fire-safe

with more desirable properties is concentrated at the

University of Massachusetts Amherst The University of Massachusetts Amherst (UMass Amherst, UMass) is a public research university in Amherst, Massachusetts and the sole public land-grant university in Commonwealth of Massachusetts. Founded in 1863 as an agricultural college, ...

and at the

Federal Aviation Administration The Federal Aviation Administration (FAA) is the largest transportation agency of the U.S. government and regulates all aspects of civil aviation in the country as well as over surrounding international waters. Its powers include air traffic ...

where a long-term research program on developing fire-safe

was begun in 1995. The Center for UMass/Industry Research on Polymers (CUMIRP) was established in 1980 in Amherst, MA as a concentrated cluster of scientists from both academia and industry for the purpose of

science and engineering research.

History

Early history

Controlling the

of different materials has been a subject of interest since 450 B.C. when Egyptians attempted to reduce the

of wood by soaking it in potassium aluminum sulfate ( alum). Between 450 B.C. and the early 20th century, other materials used to reduce the flammability of different materials included mixtures of alum and

vinegar Vinegar is an aqueous solution of acetic acid and trace compounds that may include flavorings. Vinegar typically contains 5–8% acetic acid by volume. Usually, the acetic acid is produced by a double fermentation, converting simple sugars to eth ...

;

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

and hair;

and

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, blackboard or sidewalk chalk, and drywal ...

; alum,

ferrous sulfate Iron(II) sulfate (British English: iron(II) sulphate) or ferrous sulfate denotes a range of salts with the formula Fe SO4·''x''H2O. These compounds exist most commonly as the hepta hydrate (''x'' = 7) but several values for x are kn ...

, and

; and ammonium chloride,

ammonium phosphate Ammonium phosphate is the inorganic compound with the formula (NH4)3PO4. It is the ammonium salt of orthophosphoric acid. A related "double salt", (NH4)3PO4.(NH4)2HPO4 is also recognized but is impractical use. Both triammonium salts evolve ammoni ...

borax Borax is a salt ( ionic compound), a hydrated borate of sodium, with chemical formula often written . It is a colorless crystalline solid, that dissolves in water to make a basic solution. It is commonly available in powder or granular for ...

, and various

acids In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a ...

. These early attempts found application in reducing the flammability of wood for military materials, theater curtains, and other textiles, for example. Important milestones during this early work include the first

patent A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A ...

for a mixture for controlling flammability issued to Obadiah Wyld in 1735, and the first scientific exploration of controlling flammability, which was undertaken by

Joseph Louis Gay-Lussac Joseph Louis Gay-Lussac (, , ; 6 December 1778 – 9 May 1850) was a French chemist and physicist. He is known mostly for his discovery that water is made of two parts hydrogen and one part oxygen (with Alexander von Humboldt), for two laws ...

in 1821.

Developments since WWII

Research on fire-retardant

was bolstered by the need for new types of synthetic polymers in

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

. The combination of a

halogenated In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transformation important, e.g. in the production of polymers, ...

paraffin Paraffin may refer to: Substances * Paraffin wax, a white or colorless soft solid that is used as a lubricant and for other applications * Liquid paraffin (drug), a very highly refined mineral oil used in cosmetics and for medical purposes * Alkan ...

and antimony oxide was found to be successful as a

fire retardant A fire retardant is a substance that is used to slow down or stop the spread of fire or reduce its intensity. This is commonly accomplished by chemical reactions that reduce the flammability of fuels or delay their combustion. Fire retardants m ...

for canvas tenting. Synthesis of

, such as

polyesters Polyester is a category of polymers that contain the ester functional group in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include natural ...

, with

monomers were also developed around this time.Robitschek, P.; Bean, C. T. Flame-Resistant Polyesters from Hexachlorocyclopentadiene. ''Ind. Eng. Chem.'' 1954, ''46'' (8), 1628-1632

Incorporating flame-resistant additives into

became a common and relatively cheap way to reduce the flammability of

,Connolly, W. J.; Thornton, A. M. Aluminum Hydrate Filler in Polyester Systems. ''Mod. Plastics'' 1965, ''43'' (2), 154-202. while synthesizing intrinsically fire-resistant

has remained a more expensive alternative, although the properties of these

are usually more efficient at deterring

combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combus ...

Polymer combustion

General mechanistic scheme

Traditional

decompose Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is ...

under heat and produce combustible products; thus, they are able to originate and easily propagate

(as shown in Figure 1). The

process begins when heating a

yields volatile products. If these products are sufficiently concentrated, within the

flammability limits Mixtures of dispersed combustible materials (such as gaseous or vaporised fuels, and some dusts) and oxygen in the air will burn only if the fuel concentration lies within well-defined lower and upper bounds determined experimentally, referred to a ...

, and at a temperature above the ignition temperature, then

proceeds. As long as the heat supplied to the

remains sufficient to sustain its

thermal decomposition Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is re ...

at a rate exceeding that required to feed the flame,

will continue.Camino, G.; Costa, L.; Luda di Cortemiglia, M. P. Overview of Fire Retardant Mechanisms. ''Polym. Degrad. Stabil.'' 1991, ''33'' (2), 131-154

Purpose and methods of fire-retardant systems

The purpose is to control heat below the critical level. To achieve this, one can create an

endothermic In thermochemistry, an endothermic process () is any thermodynamic process with an increase in the enthalpy (or internal energy ) of the system.Oxtoby, D. W; Gillis, H.P., Butler, L. J. (2015).''Principle of Modern Chemistry'', Brooks Cole. ...

environment, produce non-combustible products, or add chemicals that would remove fire-propagating radicals (H and OH), to name a few. These specific chemicals can be added into the

molecules permanently (see Intrinsically Fire-Resistant Polymers) or as additives and fillers (see Flame-Retardant Additives and Fillers).

Role of oxygen

Oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

catalyzes the

pyrolysis The pyrolysis (or devolatilization) process is the thermal decomposition of materials at elevated temperatures, often in an inert atmosphere. It involves a change of chemical composition. The word is coined from the Greek-derived elements ''py ...

at low concentration and initiates

oxidation Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is the gain of electrons or a ...

at high concentration. Transition concentrations are different for different

. (e.g.,

polypropylene Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene. Polypropylene belongs to the group of polyolefins a ...

, between 5% and 15%). Additionally,

exhibit a structural-dependent relationship with

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

. Some structures are intrinsically more sensitive to

upon reaction with

. The amount of access that

has to the surface of the

also plays a role in

is better able to interact with the

before a flame has actually been ignited.

Role of heating rate

In most cases, results from a typical heating rate (e.g. 10℃/min for mechanical

thermal degradation Thermal decomposition, or thermolysis, is a chemical decomposition caused by heat. The decomposition temperature of a substance is the temperature at which the substance chemically decomposes. The reaction is usually endothermic as heat is req ...

studies) do not differ significantly from those obtained at higher heating rates. The extent of reaction can, however, be influenced by the heating rate. For example, some reactions may not occur with a low heating rate due to evaporation of the products.

Role of pressure

Volatile products are removed more efficiently under low pressure, which means the stability of the

might have been compromised. Decreased pressure also slows down

of high boiling products.

Intrinsically fire-resistant polymers

The

that are most efficient at resisting

are those that are synthesized as intrinsically fire-resistant. However, these types of

can be difficult as well as costly to synthesize. Modifying different properties of the

can increase their intrinsic fire-resistance; increasing rigidity or stiffness, the use of

polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates * Polar climate, the c ...

monomers In chemistry, a monomer ( ; ''mono-'', "one" + '' -mer'', "part") is a molecule that can react together with other monomer molecules to form a larger polymer chain or three-dimensional network in a process called polymerization. Classification Mo ...

, and/or

hydrogen bonding In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a l ...

between the

chains can all enhance fire-resistance.Frazer, A.H. ''High Temperature Resistant Polymers;'' John Wiley & Sons: New York, 1968

Linear, single-stranded polymers with cyclic aromatic components

Most intrinsically fire-resistant

are made by incorporation of aromatic cycles or heterocycles, which lend rigidity and stability to the

.Mallakpour, S. E.; Hajipour, A.-R.; Mahdavian, A.-R.; Khoee, S. Synthesis and characterization of novel optically active and flame-retardant heterocyclic polyimides. ''J. Appli. Polym. Sci.'' 2000, ''76'' (2), 240-248. Polyimides, polybenzoxazoles (PBOs), polybenzimidazoles, and polybenzthiazoles (PBTs) are examples of

made with aromatic heterocycles (Figure 2).

Polymers A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic an ...

made with aromatic monomers have a tendency to condense into chars upon

, decreasing the amount of flammable gas that is released. Syntheses of these types of

generally employ prepolymers which are further reacted to form the fire-resistant

.Akinseye, T. D.; Harruna, I. I.; Bota, K. B. Processable Precursors .4. Synthesis and Characterization of Processable Precursors to Poly (Phenylene Bixbenzoxazoles). ''Polymer'' 1997, ''38'' (10), 2507-2513

Ladder polymers

Ladder polymer In chemistry, a ladder polymer is a type of double stranded polymer with the connectivity of a ladder. In a typical one-dimensional polymer, e.g. polyethylene and polysiloxanes, the monomers form two bonds, giving a chain. In a ladder polymer the ...

s are a subclass of

made with aromatic cycles or heterocycles. Ladder

generally have one of two types of general structures, as shown in Figure 3.
One type of ladder

links two

chains with periodic

covalent bonds A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...

.Sirkecioglu, O.; Tunca, A. A.; Talinli, N.; Akar, A. Ladder type polymers from dihydroxyaromatic compounds and dialdehydes. ''Angew. Makrom. Chem.'' 1999, ''271'' (1), 8-10. In another type, the ladder

consists of a single chain that is double-stranded. Both types of ladder

exhibit good resistance to

from heat because the chains do not necessarily fall apart if one covalent bond is broken. However, this makes the processing of ladder

difficult because they are not easily melted. These difficulties are compounded because ladder polymers are often highly

insoluble In chemistry, solubility is the ability of a substance, the solute, to form a solution with another substance, the solvent. Insolubility is the opposite property, the inability of the solute to form such a solution. The extent of the solubil ...

Inorganic and semiorganic polymers

Inorganic and semiorganic

often employ

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

, boron-

, and

phosphorus Phosphorus is a chemical element with the symbol P and atomic number 15. Elemental phosphorus exists in two major forms, white phosphorus and red phosphorus, but because it is highly reactive, phosphorus is never found as a free element on Ear ...

monomers. The non-burning characteristics of the

inorganic In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemist ...

components of these

contribute to their controlled

. For example, instead of forming toxic, flammable gasses in abundance,

prepared with incorporation of cyclotriphosphazene rings give a high char yield upon

. Polysialates (

containing frameworks of

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

, and

) are another type of

that can be thermally stable up to temperatures of 1300-1400 °C.Barbosa, V. F. F.; MacKenzie, K. J. D.; Thaumaturgo, C. Synthesis and characterization of materials based on inorganic polymers of alumina and silica: sodium polysialate polymers. ''Int. J. Inorg. Mater.'' 2000, ''2'' (4), 309-317.

Flame-retardant additives and fillers

Additives are divided into two basic types depending on the interaction of the additive and

. Reactive

flame retardant The term flame retardants subsumes a diverse group of chemicals that are added to manufactured materials, such as plastics and textiles, and surface finishes and coatings. Flame retardants are activated by the presence of an ignition source and ...

s are compounds that are chemically built into the

. They usually contain heteroatoms. Additive

s, on the other hand, are compounds that are not

covalently A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atom ...

bound to the

; the flame retardant and the

are just physically mixed together. Only a few elements are being widely used in this field:

antimony Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient t ...

chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...

bromine Bromine is a chemical element with the symbol Br and atomic number 35. It is the third-lightest element in group 17 of the periodic table ( halogens) and is a volatile red-brown liquid at room temperature that evaporates readily to form a simi ...

, and in specific applications

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...

zinc Zinc is a chemical element with the symbol Zn and atomic number 30. Zinc is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodi ...

and

carbon Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...

. One prominent advantage of the flame retardants (FRs) derived from these elements is that they are relatively easy to manufacture. They are used in important quantities: in 2013, the world consumption of FRs amounted to around 1.8/2.1 Mio t for 2013 with sales of 4.9/5.2 billion USD. Market studies estimate FRs demand to rise between 5/7 % pa to 2.4/2.6 Mio t until 2016/2018 with estimated sales of 6.1/7.1 billion USD. The most important flame retardants systems used act either in the gas phase where they remove the high energy radicals H and OH from the flame or in the solid phase, where they shield the polymer by forming a charred layer and thus protect the polymer from being attacked by oxygen and heat. Flame retardants based on bromine or chlorine, as well as a number of phosphorus compounds act chemically in the gas phase and are very efficient. Others only act in the condensed phase such as metal hydroxides ( aluminum trihydrate, or ATH, magnesium hydroxide, or MDH, and boehmite), metal oxides and salts (zinc borate and zinc oxide, zinc hydroxystannate), as well as expandable graphite and some nanocomposites (see below). Phosphorus and nitrogen compounds are also effective in the condensed phase, and as they also may act in the gas phase, they are quite efficient flame retardants. Overviews of the main flame retardants families, their mode of action and applications are given in. Further handbooks on these topics are A good example for a very efficient phosphorus-based flame retardant system acting in the gas and condensed phases is

aluminium diethyl phosphinate Aluminium diethyl phosphinate is a chemical compound with formula Al()3. It decomposes above 300 °C. Applications In the family of dialkyl phosphinic acid salts, aluminium diethyl phosphinate has been found to be an excellent flame retar ...

in conjunction with synergists such as melamine polyphosphate (MPP) and others. These phosphinates are mainly used to flame retard polyamides (PA) and polybutylene terephthalate (PBT) for flame retardant applications in electrical engineering/electronics (E&E).Huang, K.J., Hörold, S., Dietz, M., Schmitt, E. Phosphinates as flame retardants for plastics in electronics. 1st International SKZ Conference on Flame Retardant Plastics, Shanghai, China, 21 September 2009

Natural fiber-containing composites

Besides providing satisfactory mechanical properties and renewability, natural fibers are easier to obtain and much cheaper than man-made materials. Moreover, they are more environmentally friendly.Kozlowski, R.; Wladyka-Przybylak, M. Flammability and fire resistance of composites reinforced by natural fibers. ''Polymer Advan. Technol.'' 2008, ''19'' (6), 446-453

Recent research focuses on application of different types of

s during the manufacturing process as well as applications of

s (especially

intumescent An intumescent is a substance that swells as a result of heat exposure, leading to an increase in volume and decrease in density. Intumescent materials are typically used in passive fire protection and require listing, approval, and compliance in ...

coatings) at the finishing stage.

Nanocomposites

Nanocomposites have become a hotspot in the research of fire-safe

because of their relatively low cost and high flexibility for multifunctional properties.Bourbigot, S.; Duquesne, S.; Jama C. Polymer Nanocomposites: How to Reach Low Flammability? ''Macromol. Symp.'' 2006, ''233'' (1), 180-190

Gilman and colleagues did the pioneering work by demonstrating the improvement of fire-retardancy by having nanodispersed

montmorillonite Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite gro ...

clay in the polymer matrix. Later, organomodified

clays Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay par ...

, TiO₂ nanoparticles,

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

nanoparticles,

layered double hydroxides Layered double hydroxides (LDH) are a class of ionic solids characterized by a layered structure with the generic layer sequence cB Z AcBsub>''n'', where c represents layers of metal cations, A and B are layers of hydroxide () anions, and Z are l ...

carbon nanotubes A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon na ...

and polyhedral

silsesquioxane 220x220px, thumbnail, A cubic silsesquioxane. A silsesquioxane is an organosilicon compound with the chemical formula SiO3/2sub>n (R = H, alkyl, aryl, alkenyl or alkoxyl.). Silsesquioxanes are colorless solids that adopt cage-like or polymeric ...

s were proved to work as well. Recent research has suggested that combining nanoparticles with traditional

s (e.g.,

s) or with surface treatment (e.g., plasma treatment) effectively decreases

Problems with additives and fillers

Although effective at reducing

, flame-retardant additives and fillers have disadvantages as well. Their poor compatibility, high volatility and other deleterious effects can change properties of

. Besides, addition of many fire-retardants produces

soot Soot ( ) is a mass of impure carbon particles resulting from the incomplete combustion of hydrocarbons. It is more properly restricted to the product of the gas-phase combustion process but is commonly extended to include the residual pyrolysed ...

and

carbon monoxide Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...

during

. Halogen-containing materials cause even more concerns on environmental

pollution Pollution is the introduction of contaminants into the natural environment that cause adverse change. Pollution can take the form of any substance (solid, liquid, or gas) or energy (such as radioactivity, heat, sound, or light). Pollutants, the ...

.Porter, D.; Metcalfe, E.; Thomas, M. J. K. Nanocomposite Fire Retardants – A Review. ''Fire Mater.'' 2000, ''24'' (1), 45-52.

References

{{reflist

External links

Fire-Safety Branch of the Federal Aviation Administration
Polymers Fire protection Flame retardants

History

Early history

Developments since WWII

Polymer combustion

General mechanistic scheme

Purpose and methods of fire-retardant systems

Role of oxygen

Role of heating rate

Role of pressure

Intrinsically fire-resistant polymers

Linear, single-stranded polymers with cyclic aromatic components

Ladder polymers

Inorganic and semiorganic polymers

Flame-retardant additives and fillers

Natural fiber-containing composites

Nanocomposites

Problems with additives and fillers

See also

References

External links