Aramid
Encyclopedia
Synthetic fiber
Synthetic fibers are the result of extensive research by scientists to improve on naturally occurring animal and plant fibers. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes into the air, forming a thread...
s. They are used in aerospace and military applications, for ballistic rated body armor
Bulletproof vest
A ballistic vest, bulletproof vest or bullet-resistant vest is an item of personal armor that helps absorb the impact from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso...
fabric and ballistic composites, in bicycle tires, and as an asbestos
Asbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
substitute. The name is a portmanteau of "aromatic 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,...
". They are fibers in which the chain molecules are highly oriented along the fiber axis, so the strength of the chemical bond
Chemical bond
A chemical bond is an attraction between atoms that allows the formation of chemical substances that contain two or more atoms. The bond is caused by the electromagnetic force attraction between opposite charges, either between electrons and nuclei, or as the result of a dipole attraction...
can be exploited.
History
Aromatic polyamides were first introduced in commercial applications in the early 1960s, with a metaMeta- (chemistry)
In chemistry, meta is a prefix, used for systematic names in IUPAC nomenclature. It has several meanings. *In organic chemistry, meta indicates the positions of substituents in aromatic cyclic compounds...
-aramid fiber produced by DuPont
DuPont
E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...
as HT-1 and then under the trade name Nomex
Nomex
Nomex is a registered trademark for flame resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967.- Properties:...
. This fiber, which handles similarly to normal textile apparel fibers, is characterized by its excellent resistance to heat, as it neither melts nor ignites in normal levels of oxygen. It is used extensively in the production of protective apparel, air filtration, thermal and electrical insulation as well as a substitute for asbestos
Asbestos
Asbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
. Meta-aramid is also produced in the Netherlands and Japan by Teijin
Teijin
is a Japanese chemical and pharmaceutical company. It is listed on the Tokyo Stock Exchange with a market capitalisation of USD 3.9 billion. It operates in five main business segments: synthetic fibres; films and plastics; pharmaceuticals and home health care; trading and retail; and IT and new...
under the trade name Conex, in China by Yantai under the trade name New Star
New star
New star or New Star may refer to:*Star formation, a process of in which new stars are formed*Henderson New Star, formerly New Star Asset Management*New Star Games, an independent video game developer...
, by SRO Group (China) under the trade name X-Fiper, and a variant of meta-aramid in France by Kermel under the trade name Kermel.
Based on earlier research by Monsanto Company and Bayer
Bayer
Bayer AG is a chemical and pharmaceutical company founded in Barmen , Germany in 1863. It is headquartered in Leverkusen, North Rhine-Westphalia, Germany and well known for its original brand of aspirin.-History:...
, a fiber – para-aramid – with much higher tenacity
Tensile strength
Ultimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
and elastic modulus
Elastic modulus
An elastic modulus, or modulus of elasticity, is the mathematical description of an object or substance's tendency to be deformed elastically when a force is applied to it...
was also developed in the 1960s–1970s by DuPont and Akzo Nobel
Akzo Nobel
Akzo Nobel N.V., trading as AkzoNobel, is a Dutch multinational, active in the fields of decorative paints, performance coatings and specialty chemicals. Headquartered in Amsterdam, the company has activities in more than 80 countries, and employs approximately 55,000 people. Sales in 2010 were EUR...
, both profiting from their knowledge of rayon, polyester and nylon processing.
Much work was done by Stephanie Kwolek
Stephanie Kwolek
Stephanie Louise Kwolek is a Polish-American chemist who invented poly-paraphenylene terephtalamide—better known as Kevlar. She was born in the Pittsburgh suburb of New Kensington, Pennsylvania. Kwolek has won numerous awards for her work in polymer chemistry.- Early life and education :Kwolek was...
in 1961 while working at DuPont, and that company was the first to introduce a para-aramid called Kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
in 1973. A similar fiber called Twaron
Twaron
Twaron is the brandname of Teijin Aramid for a para-aramid. It is a heat-resistant and strong synthetic fibre developed in the early 1970s by the Dutch company AKZO, division Enka, later Akzo Industrial Fibers. The research name of the para-aramid fibre was originally Fiber X, but it was soon...
with roughly the same chemical structure was introduced by Akzo in 1978. Due to earlier patents on the production process, Akzo and DuPont engaged in a patent dispute in the 1980s. Twaron is currently owned by the Teijin
Teijin Aramid
Teijin Aramid, formerly known as Teijin Twaron, is a company in The Netherlands that produces various high-strength fibers for industrial purposes, most notably their Kevlar-like para-aramid, Twaron. Twaron finds applications in numerous markets, such as automotive , aerospace, civil engineering,...
company (see Production).
Para-aramids are used in many high-tech applications, such as aerospace and military applications, for "bullet-proof" body armor
Bulletproof vest
A ballistic vest, bulletproof vest or bullet-resistant vest is an item of personal armor that helps absorb the impact from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso...
fabric.
The Federal Trade Commission
Federal Trade Commission
The Federal Trade Commission is an independent agency of the United States government, established in 1914 by the Federal Trade Commission Act...
definition for aramid fiber is:
A manufactured fiber in which the fiber-forming substance is a long-chain synthetic polyamide in which at least 85% of the amide linkages, (-CO-NH-)Peptide bondThis article is about the peptide link found within biological molecules, such as proteins. A similar article for synthetic molecules is being created...
are attached directly to two aromatic rings.
Production
World capacity of para-aramid production is estimated at about 41,000 tonneTonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
s/year in 2002 and increases each year by 5–10%. In 2007 this means a total production capacity of around 55,000 tonnes/year.
Polymer preparation
Aramids are generally prepared by the reaction between an amine group and a carboxylic acid halide group. Simple AB homopolymers may look like:- nNH2-Ar-COCl → -(NH-Ar-CO)n- + nHCl
The most well-known aramids (Kevlar
Kevlar
Kevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
, Twaron
Twaron
Twaron is the brandname of Teijin Aramid for a para-aramid. It is a heat-resistant and strong synthetic fibre developed in the early 1970s by the Dutch company AKZO, division Enka, later Akzo Industrial Fibers. The research name of the para-aramid fibre was originally Fiber X, but it was soon...
, Nomex
Nomex
Nomex is a registered trademark for flame resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967.- Properties:...
, New Star and Teijinconex) are AABB polymers. Nomex, Teijinconex and New Star contain predominantly the meta-linkage and are poly-metaphenylene isophtalamides (MPIA).
Kevlar and Twaron are both p-phenylene terephtalamides (PPTA), the simplest form of the AABB para-polyaramide. PPTA is a product of p-phenylene diamine (PPD
P-Phenylenediamine
p-Phenylenediamine is an organic compound with the formula C6H42. This derivative of aniline is a colorless solid, but typically samples can contain yellowish impurities arising from oxidation. It is mainly used as a component of engineering polymers and composites. It is also an ingredient in...
) and terephtaloyl dichloride (TDC or TCl)
Terephthaloyl chloride
Terephthaloyl chloride is the acid chloride of terephthalic acid and is one of two monomers used to make Kevlar, the other being p-phenylenediamine...
.
Production of PPTA relies on a co-solvent with an ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
ic component (calcium chloride
Calcium chloride
Calcium chloride, CaCl2, is a salt of calcium and chlorine. It behaves as a typical ionic halide, and is solid at room temperature. Common applications include brine for refrigeration plants, ice and dust control on roads, and desiccation...
(CaCl2)) to occupy the hydrogen bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...
s of the amide groups, and an organic component (N-methyl pyrrolidone (NMP)
Methylpyrrolidone
N-Methyl-2-pyrrolidone is a chemical compound with 5-membered lactam structure. It is a clear to slightly yellow liquid miscible with water and solvents like ethyl acetate, chloroform, benzene and lower alcohols or ketones. It also belongs to the class of dipolar aprotic solvents which includes...
) to dissolve the aromatic polymer
Polymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
. Prior to the invention of this process by Leo Vollbracht, who worked at the Dutch chemical firm Akzo, no practical means of dissolving the polymer was known. The use of this system led to an extended patent dispute between Akzo and DuPont.
Spinning
After production of the polymer, the aramid fiber is produced by spinningSpinneret (polymers)
Spinneret refers to a multi-pored device through which a plastic polymer melt is extruded to form fibers. Streams of viscous polymer usually exit into cool air or liquid to solidify. The individual polymer chains tend to align in the fiber because of viscous flow. This airstream liquid-to-fiber...
the solved polymer to a solid
Solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...
fiber from a liquid
Liquid
Liquid is one of the three classical states of matter . Like a gas, a liquid is able to flow and take the shape of a container. Some liquids resist compression, while others can be compressed. Unlike a gas, a liquid does not disperse to fill every space of a container, and maintains a fairly...
chemical blend. Polymer solvent for spinning PPTA is generally 100% anhydrous sulfuric acid
Sulfuric acid
Sulfuric acid is a strong mineral acid with the molecular formula . Its historical name is oil of vitriol. Pure sulfuric acid is a highly corrosive, colorless, viscous liquid. The salts of sulfuric acid are called sulfates...
(H2SO4).
Other types of aramids
Besides meta-aramids like Nomex, other variations belong to the aramid fiber range. These are mainly of the copolyamide type, best known under the brand name TechnoraTechnora
Technora is an Aramid that is useful for a variety of applications that require high strength or chemical resistance. It is a brandname of the company Teijin.-Production:...
, as developed by Teijin
Teijin
is a Japanese chemical and pharmaceutical company. It is listed on the Tokyo Stock Exchange with a market capitalisation of USD 3.9 billion. It operates in five main business segments: synthetic fibres; films and plastics; pharmaceuticals and home health care; trading and retail; and IT and new...
and introduced in 1976. The manufacturing process of Technora reacts PPD
P-Phenylenediamine
p-Phenylenediamine is an organic compound with the formula C6H42. This derivative of aniline is a colorless solid, but typically samples can contain yellowish impurities arising from oxidation. It is mainly used as a component of engineering polymers and composites. It is also an ingredient in...
and 3,4'-diaminodiphenylether (3,4'-ODA) with terephtaloyl chloride (TCl)
Terephthaloyl chloride
Terephthaloyl chloride is the acid chloride of terephthalic acid and is one of two monomers used to make Kevlar, the other being p-phenylenediamine...
.
This relatively simple process uses only one amide solvent and therefore spinning can be done directly after the polymer production.
Aramid fiber characteristics
Aramids share a high degree of orientation with other fibers such as ultra high molecular weight polyethyleneUltra high molecular weight polyethylene
Ultra-high-molecular-weight polyethylene , also known as high-modulus polyethylene or high-performance polyethylene , is a subset of the thermoplastic polyethylene. It has extremely long chains, with molecular weight numbering in the millions, usually between 2 and 6 million...
, a characteristic which dominates their properties.
General
- good resistance to abrasion
- good resistance to organic solvents
- nonconductive
- no melting pointMelting pointThe melting point of a solid is the temperature at which it changes state from solid to liquid. At the melting point the solid and liquid phase exist in equilibrium. The melting point of a substance depends on pressure and is usually specified at standard atmospheric pressure...
, degradation starts from 500°C - low flammability
- good fabric integrity at elevated temperatureTemperatureTemperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
s - sensitive to acids and salts
- sensitive to ultravioletUltravioletUltraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiationRadiationIn physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing... - prone to static build-up unless finished
Para-aramids
- para-aramid fibers such as Kevlar and Twaron, provide outstanding strength-to-weight properties
- high Young's modulusYoung's modulusYoung's modulus is a measure of the stiffness of an elastic material and is a quantity used to characterize materials. It is defined as the ratio of the uniaxial stress over the uniaxial strain in the range of stress in which Hooke's Law holds. In solid mechanics, the slope of the stress-strain...
- high tenacityTensile strengthUltimate tensile strength , often shortened to tensile strength or ultimate strength, is the maximum stress that a material can withstand while being stretched or pulled before necking, which is when the specimen's cross-section starts to significantly contract...
- low creepCreep (deformation)In materials science, creep is the tendency of a solid material to slowly move or deform permanently under the influence of stresses. It occurs as a result of long term exposure to high levels of stress that are below the yield strength of the material....
- low elongation at break (~3.5%)
- difficult to dye – usually solution dyed
Major industrial uses
- flame-resistant clothingClothingClothing refers to any covering for the human body that is worn. The wearing of clothing is exclusively a human characteristic and is a feature of nearly all human societies...
- heat protective clothing and helmetHelmetA helmet is a form of protective gear worn on the head to protect it from injuries.Ceremonial or symbolic helmets without protective function are sometimes used. The oldest known use of helmets was by Assyrian soldiers in 900BC, who wore thick leather or bronze helmets to protect the head from...
s - body armorBulletproof vestA ballistic vest, bulletproof vest or bullet-resistant vest is an item of personal armor that helps absorb the impact from firearm-fired projectiles and shrapnel from explosions, and is worn on the torso...
, competing with PEPolyethylenePolyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
based fiber products such as Dyneema and SpectraUltra high molecular weight polyethyleneUltra-high-molecular-weight polyethylene , also known as high-modulus polyethylene or high-performance polyethylene , is a subset of the thermoplastic polyethylene. It has extremely long chains, with molecular weight numbering in the millions, usually between 2 and 6 million... - composite materialComposite materialComposite materials, often shortened to composites or called composition materials, are engineered or naturally occurring materials made from two or more constituent materials with significantly different physical or chemical properties which remain separate and distinct at the macroscopic or...
s - asbestosAsbestosAsbestos is a set of six naturally occurring silicate minerals used commercially for their desirable physical properties. They all have in common their eponymous, asbestiform habit: long, thin fibrous crystals...
replacement (e.g. brake liningBrake liningBrake linings are the consumable surfaces in brake systems, such as drum brakes and disc brakes used in transport vehicles.-History:Brake linings were invented by Bertha Benz during her historic first long distance car trip in the world in August 1888.-Structure and function:Brake linings are...
s) - hot air filtrationFiltrationFiltration is commonly the mechanical or physical operation which is used for the separation of solids from fluids by interposing a medium through which only the fluid can pass...
fabricTextileA textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...
s - tireTireA tire or tyre is a ring-shaped covering that fits around a wheel rim to protect it and enable better vehicle performance by providing a flexible cushion that absorbs shock while keeping the wheel in close contact with the ground...
s, newly as Sulfron (sulfur modified Twaron) - mechanical rubberRubberNatural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
goods reinforcement - ropeRopeA rope is a length of fibres, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength...
s and cableCableA 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 - wicks for fire dancingFire dancingFire dancing is a group of performance arts or disciplines that involve manipulation of objects on fire...
- optical fiber cable systems
- sailSailA sail is any type of surface intended to move a vessel, vehicle or rotor by being placed in a wind—in essence a propulsion wing. Sails are used in sailing.-History of sails:...
cloth (not necessarily racing boatBoatA boat is a watercraft of any size designed to float or plane, to provide passage across water. Usually this water will be inland or in protected coastal areas. However, boats such as the whaleboat were designed to be operated from a ship in an offshore environment. In naval terms, a boat is a...
sails) - sportSportA Sport is all forms of physical activity which, through casual or organised participation, aim to use, maintain or improve physical fitness and provide entertainment to participants. Sport may be competitive, where a winner or winners can be identified by objective means, and may require a degree...
ing goods - drumDrumThe drum is a member of the percussion group of musical instruments, which is technically classified as the membranophones. Drums consist of at least one membrane, called a drumhead or drum skin, that is stretched over a shell and struck, either directly with the player's hands, or with a...
heads - wind instrument reedReed (instrument)A reed is a thin strip of material which vibrates to produce a sound on a musical instrument. The reeds of most Woodwind instruments are made from Arundo donax or synthetic material; tuned reeds are made of metal or synthetics.-Single reeds:Single reeds are used on the mouthpieces of clarinets...
s, such as the Fibracell brand - loudspeakerLoudspeakerA loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
diaphragms - boathull material
- fiber reinforced concreteFiber reinforced concreteFiber-reinforced concrete is concrete containing fibrous material which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers...
- reinforced thermoplastic pipeReinforced thermoplastic pipeRTP is a generic term referring to a reelable high strength synthetic fibre reinforced thermoplastic pipe, initially developed in the early 1990s by Wavin Repox, Akzo Nobel and by Tubes d'Aquitaine from France, who developed the first pipes reinforced with synthetic fibre to replace medium...
s - tennis strings (e.g. by Ashaway and Prince tennis companies)
- hockey sticks (normally in composition with such materials as wood and carbon)
- snowboards
- jet engineJet engineA jet engine is a reaction engine that discharges a fast moving jet to generate thrust by jet propulsion and in accordance with Newton's laws of motion. This broad definition of jet engines includes turbojets, turbofans, rockets, ramjets, pulse jets...
enclosures
See also
Para-aramid- KevlarKevlarKevlar is the registered trademark for a para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. Developed at DuPont in 1965, this high strength material was first commercially used in the early 1970s as a replacement for steel in racing tires...
- TechnoraTechnoraTechnora is an Aramid that is useful for a variety of applications that require high strength or chemical resistance. It is a brandname of the company Teijin.-Production:...
- TwaronTwaronTwaron is the brandname of Teijin Aramid for a para-aramid. It is a heat-resistant and strong synthetic fibre developed in the early 1970s by the Dutch company AKZO, division Enka, later Akzo Industrial Fibers. The research name of the para-aramid fibre was originally Fiber X, but it was soon...
- Heracron
Meta-aramid
- NomexNomexNomex is a registered trademark for flame resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967.- Properties:...
Others
- Innegra SInnegra SInnegra S is the brandname of Innegrity for a polyolefin .-History:Dr. Brian Morin, current CEO of Innegrity began work on Innegra in 2004...
- NylonNylonNylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station...
- TextileTextileA textile or cloth is a flexible woven material consisting of a network of natural or artificial fibres often referred to as thread or yarn. Yarn is produced by spinning raw fibres of wool, flax, cotton, or other material to produce long strands...
- Ultra high molecular weight polyethyleneUltra high molecular weight polyethyleneUltra-high-molecular-weight polyethylene , also known as high-modulus polyethylene or high-performance polyethylene , is a subset of the thermoplastic polyethylene. It has extremely long chains, with molecular weight numbering in the millions, usually between 2 and 6 million...