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Kevlar (para-aramid) is a strong, heat-resistant
synthetic fiber Synthetic fibers or synthetic fibres (in British English; see spelling differences) are fibers made by humans through chemical synthesis, as opposed to natural fibers that are directly derived from living organisms, such as plants like cott ...
, related to other
aramid Aramid fibers, short for aromatic polyamide, are a class of heat-resistant and strong synthetic fibers. They are used in aerospace and military applications, for ballistic-rated bulletproof vest, body armor cloth, fabric and ballistic composites ...
s such as
Nomex Nomex is a trademarked term for an inherently flame-resistant fabric with meta-aramid chemistry widely used for industrial applications and fire protection equipment. It was developed in the early 1960s by DuPont and first marketed in 1967. ...
and
Technora Technora is an aramid that is useful for a variety of applications that require high strength or chemical resistance. It is a brand name of the company Teijin Aramid. Technora was used on January 25, 2004 to suspend the NASA Mars rover '' Oppor ...
. Developed by
Stephanie Kwolek Stephanie Louise Kwolek (; July 31, 1923 – June 18, 2014) was an American chemist best known for inventing Kevlar (poly-paraphenylene terephthalamide). Her career at the DuPont company spanned more than 40 years. For her discovery, Kwolek was ...
at
DuPont Dupont, DuPont, Du Pont, duPont, or du Pont may refer to: People * Dupont (surname) Dupont, also spelled as DuPont, duPont, Du Pont, or du Pont is a French surname meaning "of the bridge", historically indicating that the holder of the surname re ...
in 1965, the high-strength material was first used commercially in the early 1970s as a replacement for steel in racing tires. It is typically spun into ropes or
fabric Textile is an umbrella term that includes various fiber-based materials, including fibers, yarns, filaments, threads, and different types of fabric. At first, the word "textiles" only referred to woven fabrics. However, weaving is no ...
sheets that can be used as such, or as an ingredient in
composite material A composite or composite material (also composition material) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a ...
components. Kevlar has many applications, ranging from bicycle
tire A tire (North American English) or tyre (Commonwealth English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineeri ...
s and racing sails to
bulletproof vest A bulletproof vest, also known as a ballistic vest or bullet-resistant vest, is a type of body armor designed to absorb impact and prevent the penetration of firearm projectiles and explosion fragments to the torso. The vest can be either soft ...
s, due to its high tensile strength-to-weight ratio; by this measure it is five times stronger than steel. It is also used to make modern marching
drumhead A drumhead or drum skin is a membrane stretched over one or both of the open ends of a drum. The drumhead is struck with sticks, mallets, or hands, so that it vibrates and the sound resonates through the drum. Additionally outside of percus ...
s that withstand high impact, and for mooring lines and other underwater applications. A similar fiber,
Twaron Twaron (a brand name of Teijin Aramid) is a para-aramid, high-performance yarn. It is a heat-resistant fibre, helps in ballistic protection and cut protection. Twaron was developed in the early 1970s by the Dutch company Akzo Nobel's division E ...
, with the same chemical structure was developed by
Akzo Akzo Nobel N.V., stylised as AkzoNobel, is a Dutch multinational company which creates paints and performance coatings for both industry and consumers worldwide. Headquartered in Amsterdam, the company has activities in more than 150 countries ...
in the 1970s. Commercial production started in 1986, and Twaron is manufactured by
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 para-aramid, Twaron. Twaron finds applications in numerous markets, such as au ...
.


History

Poly-paraphenylene terephthalamide (K29) – branded Kevlar – was invented by the Polish-American chemist
Stephanie Kwolek Stephanie Louise Kwolek (; July 31, 1923 – June 18, 2014) was an American chemist best known for inventing Kevlar (poly-paraphenylene terephthalamide). Her career at the DuPont company spanned more than 40 years. For her discovery, Kwolek was ...
while working for DuPont, in anticipation of a gasoline shortage. In 1964, her group began searching for a new lightweight strong fiber to use for light, but strong, tires. The polymers she had been working with, poly-p-phenylene-terephthalate and polybenzamide, formed
liquid crystal Liquid crystal (LC) is a state of matter whose properties are between those of conventional liquids and those of solid crystals. For example, a liquid crystal can flow like a liquid, but its molecules may be oriented in a common direction as i ...
s in solution, something unique to polymers at the time. The solution was "cloudy,
opalescent Opalescence or play of color is an optical phenomena, optical phenomenon associated with the mineraloid gemstone opal,opalescent. 2019. In Noah Webster's 1828 American Dictionary of the English Language. Retrieved January 7, 2019, from https:// ...
upon being stirred, and of low
viscosity Viscosity is a measure of a fluid's rate-dependent drag (physics), resistance to a change in shape or to movement of its neighboring portions relative to one another. For liquids, it corresponds to the informal concept of ''thickness''; for e ...
" and usually was thrown away. However, Kwolek persuaded the technician, Charles Smullen, who ran the
spinneret A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and ar ...
, to test her solution, and was amazed to find that the fiber did not break, unlike
nylon Nylon is a family of synthetic polymers characterised by amide linkages, typically connecting aliphatic or Polyamide#Classification, semi-aromatic groups. Nylons are generally brownish in color and can possess a soft texture, with some varieti ...
. Her supervisor and her laboratory director understood the significance of her discovery and a new field of
polymer chemistry Polymer chemistry is a sub-discipline of chemistry that focuses on the structures, chemical synthesis, and chemical and physical properties of polymers and macromolecules. The principles and methods used within polymer chemistry are also applic ...
quickly arose. By 1971, modern Kevlar was introduced. However, Kwolek was not very involved in developing the applications of Kevlar. In 1971,
Lester Shubin Lester D. Shubin (September 27, 1925 – November 20, 2009) was an American research chemist who developed Kevlar for the use in ballistic vests. Kevlar's use in ballistic vests was later expanded for use in all types of personal armor. Life Shub ...
, who was then the Director of Science and Technology for the National Institute for Law Enforcement and Criminal Justice, suggested using Kevlar to replace nylon in bullet-proof vests. Prior to the introduction of Kevlar,
flak jacket The two components of an obsolete British military flak vest. On the left, the ballistic_nylon.html" ;"title="nylon vest. On the right, the 12 layers of ballistic nylon">nylon vest. On the right, the 12 layers of ballistic nylon that provide the ...
s made of nylon had provided much more limited protection to users. Shubin later recalled how the idea developed: "We folded it over a couple of times and shot at it. The bullets didn't go through." In tests, they strapped Kevlar onto anesthetized goats and shot at their hearts, spinal cords, livers and lungs. They monitored the goats' heart rate and blood gas levels to check for lung injuries. After 24 hours, one goat died and the others had wounds that were not life threatening. Shubin received a $5 million grant to research the use of the fabric in bullet-proof vests. Kevlar 149 was invented by
Jacob Lahijani Jacob, later known as Israel, is a Patriarchs (Bible), Hebrew patriarch of the Abrahamic religions. He first appears in the Torah, where he is described in the Book of Genesis as a son of Isaac and Rebecca. Accordingly, alongside his older frate ...
of Dupont in the 1980s.


Production

The reaction of 1,4-phenylene-diamine (''para''-phenylenediamine) with terephthaloyl chloride yielding Kevlar Kevlar is synthesized in solution from the monomers 1,4-
phenylene In organic chemistry, the phenylene group () is based on a di-substituted benzene ring ( arylene). For example, poly(''p''-phenylene) is a polymer built up from ''para''-phenylene repeating units.p. C-9, Section 11.6, Handbook of Chemistry and ...
-di
amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...
( ''para''-phenylenediamine) and
terephthaloyl chloride Terephthaloyl chloride (TCL, 1,4-benzenedicarbonyl chloride) is the acyl chloride of terephthalic acid. It is a white solid at room temperature. It is one of two precursors used to make Kevlar, the other being ''p''-phenylenediamine. TCL is us ...
in a
condensation reaction In organic chemistry, a condensation reaction is a type of chemical reaction in which two molecules are combined to form a single molecule, usually with the loss of a small molecule such as water. If water is lost, the reaction is also known as a ...
yielding
hydrochloric acid Hydrochloric acid, also known as muriatic acid or spirits of salt, is an aqueous solution of hydrogen chloride (HCl). It is a colorless solution with a distinctive pungency, pungent smell. It is classified as a acid strength, strong acid. It is ...
as a byproduct. The result has liquid-crystalline behavior, and mechanical drawing orients the polymer chains in the fiber's direction.
Hexamethylphosphoramide Hexamethylphosphoramide, often abbreviated HMPA, is a phosphoramide (an amide of phosphoric acid) with the formula This colorless liquid is used as a solvent in organic synthesis. Structure and reactivity HMPA is the oxide of tris(dimethyla ...
(HMPA) was the solvent initially used for the
polymerization In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...
, but for safety reasons, DuPont replaced it by a solution of ''N''-methyl-pyrrolidone and calcium chloride. As this process had been patented by Akzo (see above) in the production of
Twaron Twaron (a brand name of Teijin Aramid) is a para-aramid, high-performance yarn. It is a heat-resistant fibre, helps in ballistic protection and cut protection. Twaron was developed in the early 1970s by the Dutch company Akzo Nobel's division E ...
, a
patent war A patent war is a "battle" between corporations or individuals to secure patents for litigation, whether offensively or defensively. There are ongoing patent wars between the world's largest technology and software corporations. Contemporary pate ...
ensued. Kevlar production is expensive because of the difficulties arising from using concentrated
sulfuric acid Sulfuric acid (American spelling and the preferred IUPAC name) or sulphuric acid (English in the Commonwealth of Nations, Commonwealth spelling), known in antiquity as oil of vitriol, is a mineral acid composed of the elements sulfur, oxygen, ...
, needed to keep the water-insoluble polymer in solution during its synthesis and
spinning Spin or spinning most often refers to: * Spin (physics) or particle spin, a fundamental property of elementary particles * Spin quantum number, a number which defines the value of a particle's spin * Spinning (textiles), the creation of yarn or thr ...
. Several grades of Kevlar are available: * ''Kevlar K-29'' – in industrial applications, such as cables,
asbestos Asbestos ( ) is a group of naturally occurring, Toxicity, toxic, carcinogenic and fibrous silicate minerals. There are six types, all of which are composed of long and thin fibrous Crystal habit, crystals, each fibre (particulate with length su ...
replacement, tires, and brake linings. * ''Kevlar K49'' – high modulus used in cable and rope products. * ''Kevlar K100'' – colored version of Kevlar * ''Kevlar K119'' – higher-elongation, flexible and more fatigue resistant * ''Kevlar K129'' – higher tenacity for ballistic applications * ''Kevlar K149'' – highest tenacity for ballistic, armor, and aerospace applications * ''Kevlar AP'' – 15% higher tensile strength than K-29 * ''Kevlar XP'' – lighter weight resin and KM2 plus fiber combination * '' Kevlar KM2'' – enhanced ballistic resistance for armor applications The
ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...
component of sunlight degrades and decomposes Kevlar, a problem known as ''
UV degradation Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of th ...
'', and so it is rarely used outdoors without protection against sunlight.


Structure and properties

When Kevlar is
spun ''Spun'' is a 2002 American black comedy crime drama film directed by Jonas Åkerlund from an original screenplay by William De Los Santos and Creighton Vero, based on three days of De Los Santos's life in the Eugene, Oregon drug subculture. I ...
, the resulting fiber has a
tensile strength Ultimate tensile strength (also called UTS, tensile strength, TS, ultimate strength or F_\text in notation) is the maximum stress that a material can withstand while being stretched or pulled before breaking. In brittle materials, the ultimate ...
of about , and a
relative density Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...
of 1.44 (0.052 lb/in3). The polymer owes its high strength to the many inter-chain bonds. These inter-molecular
hydrogen bonds In chemistry, a hydrogen bond (H-bond) is a specific type of molecular interaction that exhibits partial covalent character and cannot be described as a purely electrostatic force. It occurs when a hydrogen (H) atom, covalently bonded to a mo ...
form between the carbonyl groups and N''H'' centers. Additional strength is derived from aromatic stacking interactions between adjacent strands. These interactions have a greater influence on Kevlar than the van der Waals interactions and chain length that typically influence the properties of other synthetic polymers and fibers such as
ultra-high-molecular-weight polyethylene Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene (HMPE), it has extremely long chains, with a molecular mass typically between 2 and 6 million amu. The l ...
. The presence of
salt In common usage, salt is a mineral composed primarily of sodium chloride (NaCl). When used in food, especially in granulated form, it is more formally called table salt. In the form of a natural crystalline mineral, salt is also known as r ...
s and certain other impurities, especially
calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...
, could interfere with the strand interactions and care is taken to avoid inclusion in its production. Kevlar's structure consists of relatively rigid molecules which tend to form mostly planar sheet-like structures rather like
silk Silk is a natural fiber, natural protein fiber, some forms of which can be weaving, woven into textiles. The protein fiber of silk is composed mainly of fibroin and is most commonly produced by certain insect larvae to form cocoon (silk), c ...
protein.


Thermal properties

Kevlar maintains its strength and resilience down to cryogenic temperatures (): in fact, it is slightly stronger at low temperatures. At higher temperatures the tensile strength is immediately reduced by about 10–20%, and after some hours the strength progressively reduces further. For example: enduring for 500 hours, its strength is reduced by about 10%; and enduring for 70 hours, its strength is reduced by about 50%.


Applications


Science

Kevlar is often used in the field of
cryogenics In physics, cryogenics is the production and behaviour of materials at very low temperatures. The 13th International Institute of Refrigeration's (IIR) International Congress of Refrigeration (held in Washington, DC in 1971) endorsed a universa ...
for its low
thermal conductivity The thermal conductivity of a material is a measure of its ability to heat conduction, conduct heat. It is commonly denoted by k, \lambda, or \kappa and is measured in W·m−1·K−1. Heat transfer occurs at a lower rate in materials of low ...
and high strength relative to other materials for
suspension Suspension or suspended may refer to: Science and engineering * Car suspension * Cell suspension or suspension culture, in biology * Guarded suspension, a software design pattern in concurrent programming suspending a method call and the calling ...
purposes. It is most often used to suspend a
paramagnetic Paramagnetism is a form of magnetism whereby some materials are weakly attracted by an externally applied magnetic field, and form internal, induced magnetic fields in the direction of the applied magnetic field. In contrast with this behavior, ...
salt enclosure from a
superconducting magnet A superconducting magnet is an electromagnet made from coils of superconducting wire. They must be cooled to cryogenic temperatures during operation. In its superconducting state the wire has no electrical resistance and therefore can conduct much ...
mandrel in order to minimize any heat leaks to the paramagnetic material. It is also used as a thermal standoff or structural support where low heat leaks are desired. A thin Kevlar window has been used by the
NA48 experiment The NA48 experiment was a series of particle physics experiments in the field of kaon physics being carried out at the North Area of the Super Proton Synchrotron at CERN. The collaboration involved over 100 physicists mostly from Western Europe ...
at
CERN The European Organization for Nuclear Research, known as CERN (; ; ), is an intergovernmental organization that operates the largest particle physics laboratory in the world. Established in 1954, it is based in Meyrin, western suburb of Gene ...
to separate a vacuum vessel from a vessel at nearly atmospheric pressure, both in diameter. The window has provided vacuum tightness combined with reasonably small amount of material (only 0.3% to 0.4% of
radiation length In particle physics, the radiation length is a characteristic of a material, related to the energy loss of high energy elementary particle, particles electromagnetically interacting with it. It is defined as the mean length (in cm) into the mate ...
).


Protection

Kevlar is a well-known component of
personal armor Body armour, personal armour (also spelled ''armor''), armoured suit (''armored'') or coat of armour, among others, is armour for a person's body: protective clothing or close-fitting hands-free shields designed to absorb or deflect physical ...
such as
combat helmet A combat helmet, also called a ballistic helmet, battle helmet, or helmet system (for some Modular design, modular accessory-centric designs) is a type of helmet designed to serve as a piece of body armor intended to protect the wearer's head du ...
s, ballistic face masks, and
ballistic vest A bulletproof vest, also known as a ballistic vest or bullet-resistant vest, is a type of body armor designed to absorb impact and prevent the penetration of firearm projectiles and Fragmentation (weaponry), explosion fragments to the torso. The ...
s. The PASGT helmet and vest that were used by
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
military forces used Kevlar as a key component in their construction. Other military uses include bulletproof face masks and
spall liner Military vehicles are commonly armoured (or armored; see spelling differences) to withstand the impact of shrapnel, bullets, shells, rockets, and missiles, protecting the personnel inside from enemy fire. Such vehicles include armoured fightin ...
s used to protect the crews of
armoured fighting vehicle An armoured fighting vehicle (British English) or armored fighting vehicle (American English) (AFV) is an armed combat vehicle protected by vehicle armour, armour, generally combining operational mobility with Offensive (military), offensive a ...
s. ''Nimitz''-class aircraft carriers use Kevlar reinforcement in vital areas. Civilian applications include: high heat resistance uniforms worn by firefighters, body armour worn by police officers, security, and police tactical teams such as
SWAT A SWAT (''Special Weapons and Tactics'') team is a generic term for a police tactical unit within the United States, though the term has also been used by other nations. SWAT units are generally trained, equipped, and deployed to res ...
.Body Armor Made with Kevlar
. (2005-0604). DuPont the Miracles of Science. Retrieved November 4, 2011
Kevlar is used to manufacture gloves, sleeves, jackets,
chaps Chaparreras or chaps () are a type of sturdy over-pants (overalls) or leggings of Mexican origin, made of leather, without a seat, made up of two separate legs that are fastened to the waist with straps or belt. They are worn over trousers and ...
and other articles of clothing designed to protect users from cuts, abrasions and heat. Kevlar-based protective gear is often considerably lighter and thinner than equivalent gear made of more traditional materials. It is used for
motorcycle safety clothing To improve motorcycle safety, many countries mandate the wearing of personal protective equipment such as protective clothing and Motorcycle helmet, helmets. Protective clothing may include certain types of jackets, gloves, Motorcycle boots, bo ...
, especially in the areas featuring padding such as the shoulders and elbows. In the sport of
fencing Fencing is a combat sport that features sword fighting. It consists of three primary disciplines: Foil (fencing), foil, épée, and Sabre (fencing), sabre (also spelled ''saber''), each with its own blade and set of rules. Most competitive fe ...
it is used in the protective jackets, breeches, plastrons and the bib of the masks. It is increasingly being used in the ''peto'', the padded covering which protects the
picador A ''picador'' (; pl. ''picadores'') is one of the pair of horse-mounted bullfighters in a Spanish-style bullfight that jab the bull with a lance. They perform in the ''tercio de varas'', which is the first of the three stages in a stylized bull ...
s' horses in the bullring. Speed skaters also frequently wear an under-layer of Kevlar fabric to prevent potential wounds from skates in the event of a fall or collision.


Sport

In '' kyudo'', or Japanese
archery Archery is the sport, practice, or skill of using a Bow and arrow, bow to shooting, shoot arrows.Paterson ''Encyclopaedia of Archery'' p. 17 The word comes from the Latin ''arcus'', meaning bow. Historically, archery has been used for hunting ...
, it may be used for
bow string A bowstring joins the two ends of the Bow and arrow, bow stave and launches the arrow. Desirable properties include light weight, strength, resistance to Abrasion (mechanical), abrasion, and resistance to water. Mass has most effect at the center ...
s, as an alternative to the more expensive
hemp Hemp, or industrial hemp, is a plant in the botanical class of ''Cannabis sativa'' cultivars grown specifically for industrial and consumable use. It can be used to make a wide range of products. Along with bamboo, hemp is among the fastest ...
. It is one of the main materials used for
paraglider Paragliding is the recreational and competitive adventure sport of flying paragliders: lightweight, free-flying, foot-launched Glider (aircraft), glider aircraft with no rigid primary structure. The pilot sits in a :wikt:harness, harness or in ...
suspension lines. It is used as an inner lining for some
bicycle tire A bicycle tire is a tire that fits on the Bicycle wheel, wheel of a bicycle or similar vehicle. These tires may also be used on tricycles, wheelchairs, and handcycles, frequently for Wheelchair racing, racing. Bicycle tires provide an importa ...
s to prevent punctures. In
table tennis Table tennis (also known as ping-pong) is a racket sport derived from tennis but distinguished by its playing surface being atop a stationary table, rather than the Tennis court, court on which players stand. Either individually or in teams of ...
, plies of Kevlar are added to custom ply blades, or paddles, in order to increase bounce and reduce weight. Tennis racquets are sometimes strung with Kevlar. It is used in sails for high performance racing boats. In 2013, with advancements in technology,
Nike Nike often refers to: * Nike, Inc., a major American producer of athletic shoes, apparel, and sports equipment * Nike (mythology), a Greek goddess who personifies victory Nike may also refer to: People * Nike (name), a surname and feminine giv ...
used Kevlar in shoes for the first time. It launched the Elite II Series, with enhancements to its earlier version of basketball shoes by using Kevlar in the
anterior Standard anatomical terms of location are used to describe unambiguously the anatomy of humans and other animals. The terms, typically derived from Latin or Greek roots, describe something in its standard anatomical position. This position pro ...
as well as the shoe laces. This was done to decrease the elasticity of the tip of the shoe in contrast to the nylon conventionally used, as Kevlar expanded by about 1% against nylon which expanded by about 30%. Shoes in this range included LeBron, HyperDunk and Zoom Kobe VII. However these shoes were launched at a price range much higher than average cost of basketball shoes. It was also used in the laces for the
Adidas Adidas AG (; stylized in all lowercase since 1949) is a German athletic apparel and footwear corporation headquartered in Herzogenaurach, Bavaria, Germany. It is the largest sportswear manufacturer in Europe, and the second largest in the ...
F50 adiZero Prime football boot. Several companies, including
Continental AG Continental AG, commonly known as Continental and colloquially as Conti, is a German multinational automotive parts manufacturing company. Headquartered in Hanover, Lower Saxony, it is the world's third- largest automotive supplier and the fo ...
, manufacture cycle tires with Kevlar to protect against punctures. Folding-bead bicycle tires, introduced to cycling by The Michelin Elan tire in 1975, along with Mavic "Module E" hook-beaded rims, used Kevlar as a bead in place of steel for weight reduction and strength. A side effect of the folding bead is a reduction in shelf and floor space needed to display cycle tires in a retail environment, as they are folded and placed in small boxes.


Music

Kevlar has also been found to have useful acoustic properties for
loudspeaker A loudspeaker (commonly referred to as a speaker or, more fully, a speaker system) is a combination of one or more speaker drivers, an enclosure, and electrical connections (possibly including a crossover network). The speaker driver is an ...
cones, specifically for bass and mid range drive units. Additionally, Kevlar has been used as a
strength member Strength may refer to: Personal trait *Physical strength, as in people or animals *Character strengths like those listed in the Values in Action Inventory *The exercise of willpower Physics * Mechanical strength, the ability to withstand ...
in fiber optic cables such as the ones used for audio data transmissions. Kevlar can be used as an acoustic core on bows for
string instruments In musical instrument classification, string instruments, or chordophones, are musical instruments that produce sound from vibrating strings when a performer strums, plucks, strikes or sounds the strings in varying manners. Musicians play some ...
. Kevlar's physical properties provide strength, flexibility, and stability for the bow's user. To date, the only manufacturer of this type of bow is CodaBow. Kevlar is also presently used as a material for tailcords (a.k.a. tailpiece adjusters), which connect the
tailpiece A tailpiece is a component on many stringed musical instruments that anchors one end of the strings, usually opposite the end with the tuning mechanism (the scroll, headstock, peghead, etc.). Function and construction The tailpiece anchors t ...
to the
endpin An endpin, more commonly spelled end pin and also called tailpin,https://www.merriam-webster.com/dictionary/endpin is the component of a cello or double bass that makes contact with the floor to support the instrument's weight. It is made of meta ...
of bowed string instruments. Kevlar is sometimes used as a material on marching snare drums. It allows for an extremely high amount of tension, resulting in a cleaner sound. There is usually a resin poured onto the Kevlar to make the head airtight, and a nylon top layer to provide a flat striking surface. This is one of the primary types of marching snare drum heads.
Remo Remo Inc. is an American musical instruments manufacturing company based in Valencia, California, and founded by Remo Belli in 1957. Products manufactured include drum kits, drumheads, drums, and drum hardware, hardware, and various percussio ...
's Falam Slam patch is made with Kevlar and is used to reinforce bass drum heads where the beater strikes. Kevlar is used in the
woodwind Woodwind instruments are a family of musical instruments within the greater category of wind instruments. Common examples include flute, clarinet, oboe, bassoon, and saxophone. There are two main types of woodwind instruments: flutes and Ree ...
reeds of Fibracell. The material of these reeds is a composite of aerospace materials designed to duplicate the way nature constructs cane reed. Very stiff but sound absorbing Kevlar fibers are suspended in a lightweight resin formulation.


Motor vehicles

Kevlar is sometimes used in structural components of cars, especially high-value performance cars such as the
Ferrari F40 The Ferrari F40 (Type F120) is a Rear mid-engine, rear-wheel-drive layout, mid-engine, rear-wheel drive sports car engineered by Nicola Materazzi with styling by Pininfarina. It was built from 1987 until 1992, with the LM and GTE race car version ...
. The chopped fiber has been used as a replacement for asbestos in
brake pad Brake pads are a component of disc brakes used in automotive and other applications. Brake pads are composed of steel backing plates with friction material bound to the surface that faces the disc brake rotors. Function Brake pads convert the ki ...
s. Aramids such as Kevlar release less airborne fibres than
asbestos Asbestos ( ) is a group of naturally occurring, Toxicity, toxic, carcinogenic and fibrous silicate minerals. There are six types, all of which are composed of long and thin fibrous Crystal habit, crystals, each fibre (particulate with length su ...
brakes and do not have the carcinogenic properties associated with asbestos.


Other uses

Fire poi on a beach in San Francisco Kevlar mooring line Wicks for
fire dancing Fire performance is a group of performance arts or skills that involve the manipulation of fire. Fire performance typically involves equipment or other objects made with one or more wicks which are designed to sustain a large enough fla ...
props are made of composite materials with Kevlar in them. Kevlar by itself does not absorb fuel very well, so it is blended with other materials such as
fiberglass Fiberglass (American English) or fibreglass (English in the Commonwealth of Nations, Commonwealth English) is a common type of fibre-reinforced plastic, fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened i ...
or
cotton Cotton (), first recorded in ancient India, is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure ...
. Kevlar's high heat resistance allows the wicks to be reused many times. Kevlar is sometimes used as a substitute for
Teflon Polytetrafluoroethylene (PTFE) is a synthetic fluoropolymer of tetrafluoroethylene, and has numerous applications because it is chemically inert. The commonly known brand name of PTFE-based composition is Teflon by Chemours, a spin-off from ...
in some non-stick frying pans. Kevlar fiber is used in rope and in cable, where the fibers are kept parallel within a
polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...
sleeve. The cables have been used in
suspension bridge A suspension bridge is a type of bridge in which the deck (bridge), deck is hung below suspension wire rope, cables on vertical suspenders. The first modern examples of this type of bridge were built in the early 1800s. Simple suspension bridg ...
s such as the bridge at
Aberfeldy, Scotland Aberfeldy () is a burgh in Perth and Kinross, Scotland, on the River Tay. A small market town, Aberfeldy is located in Highland Perthshire. It was mentioned by Robert Burns in the poem ''The Birks of Aberfeldy'' and in the Ed Sheeran song "The H ...
. They have also been used to stabilize cracking concrete cooling towers by circumferential application followed by tensioning to close the cracks. Kevlar is widely used as a protective outer sheath for
optical fiber cable A fiber-optic cable, also known as an optical-fiber cable, is an assembly similar to an electrical cable but containing one or more optical fibers that are used to carry light. The optical fiber elements are typically individually coated with p ...
, as its strength protects the cable from damage and kinking. When used in this application it is commonly known by the trademarked name Parafil. Kevlar was used by scientists at
Georgia Institute of Technology The Georgia Institute of Technology (commonly referred to as Georgia Tech, GT, and simply Tech or the Institute) is a public university, public research university and Institute of technology (United States), institute of technology in Atlanta, ...
as a base textile for an experiment in electricity-producing clothing. This was done by weaving
zinc oxide Zinc oxide is an inorganic compound with the Chemical formula, formula . It is a white powder which is insoluble in water. ZnO is used as an additive in numerous materials and products including cosmetics, Zinc metabolism, food supplements, rubbe ...
nanowire file:SnSe@SWCNT.jpg, upright=1.2, Crystalline 2×2-atom tin selenide nanowire grown inside a single-wall carbon nanotube (tube diameter ≈1 nm). A nanowire is a nanostructure in the form of a wire with the diameter of the order of a nanometre ( ...
s into the fabric. If successful, the new fabric will generate about 80 milliwatts per square meter. A retractable roof of over of Kevlar was a key part of the design of the
Olympic Stadium, Montreal Olympic Stadium (, ) is a multi-purpose stadium in Montreal, Canada, located at Olympic Park in the Hochelaga-Maisonneuve district of the city. Built in the mid-1970s as the main venue for the 1976 Summer Olympics, it is nicknamed "The Big O ...
for the
1976 Summer Olympics The 1976 Summer Olympics (), officially known as the Games of the XXI Olympiad () and officially branded as Montreal 1976 (), were an international multi-sport event held from July 17 to August 1, 1976, in Montreal, Quebec, Canada. Montreal ...
. It was spectacularly unsuccessful, as it was completed 10 years late and replaced just 10 years later in May 1998 after a series of problems. Kevlar can be found as a reinforcing layer in
rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Types of polyisoprene ...
bellows A bellows or pair of bellows is a device constructed to furnish a strong blast of air. The simplest type consists of a flexible bag comprising a pair of rigid boards with handles joined by flexible leather sides enclosing an approximately airtig ...
expansion joints A expansion joint, or movement joint, is an assembly designed to hold parts together while safely absorbing temperature-induced expansion and contraction of building materials. They are commonly found between sections of buildings, bridges, si ...
and rubber
hose A hose is a flexible hollow tube or pipe designed to carry fluids from one location to another, often from a faucet or hydrant. Early hoses were made of leather, although modern hoses are typically made of rubber, canvas, and helically wound w ...
s, for use in high temperature applications, and for its high strength. It is also found as a braid layer used on the outside of hose assemblies, to add protection against sharp objects. Some
cellphone A mobile phone or cell phone is a portable telephone that allows users to make and receive calls over a radio frequency link while moving within a designated telephone service area, unlike fixed-location phones ( landline phones). This radio ...
s (including the Motorola RAZR Family, the Motorola Droid Maxx,
OnePlus 2 The OnePlus 2 (also abbreviated as OP2) is a smartphone designed by OnePlus. It is the successor to the OnePlus One. OnePlus revealed the phone on 28 July 2015 via virtual reality, using Google's Cardboard visor and its own app. OnePlus sold ...
and Pocophone F1) have a Kevlar backplate, chosen over other materials such as carbon fiber due to its resilience and lack of interference with signal transmission. The Kevlar fiber/epoxy matrix composite materials can be used in marine current turbines (MCT) or wind turbines due to their high specific strength and light weight compared to other fibers.


Composite materials

Aramid fibers are widely used for reinforcing composite materials, often in combination with
carbon fiber Carbon fiber-reinforced polymers (American English), carbon-fibre-reinforced polymers ( Commonwealth English), carbon-fiber-reinforced plastics, carbon-fiber reinforced-thermoplastic (CFRP, CRP, CFRTP), also known as carbon fiber, carbon comp ...
and
glass fiber Glass fiber ( or glass fibre) is a material consisting of numerous extremely fine fibers of glass. Glassmakers throughout history have experimented with glass fibers, but mass manufacture of glass fiber was only made possible with the inventio ...
. The matrix for high performance composites is usually
epoxy resin Epoxy is the family of basic components or cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide functional group is also co ...
. Typical applications include
monocoque Monocoque ( ), also called structural skin, is a structural system in which loads are supported by an object's external skin, in a manner similar to an egg shell. The word ''monocoque'' is a French term for "single shell". First used for boats, ...
bodies for
Formula 1 Formula One (F1) is the highest class of worldwide racing for open-wheel single-seater formula Auto racing, racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The FIA Formula One World Championship has been one ...
cars, helicopter rotor blades,
tennis Tennis is a List of racket sports, racket sport that is played either individually against a single opponent (singles (tennis), singles) or between two teams of two players each (doubles (tennis), doubles). Each player uses a tennis racket st ...
,
table tennis Table tennis (also known as ping-pong) is a racket sport derived from tennis but distinguished by its playing surface being atop a stationary table, rather than the Tennis court, court on which players stand. Either individually or in teams of ...
,
badminton Badminton is a racquet sport played using racket (sports equipment), racquets to hit a shuttlecock across a net (device), net. Although it may be played with larger teams, the most common forms of the game are "singles" (with one player per s ...
and
squash Squash most often refers to: * Squash (sport), the high-speed racquet sport also known as squash racquets * Squash (plant), the fruit of vines of the genus ''Cucurbita'' Squash may also refer to: Sports * Squash (professional wrestling), an extr ...
rackets,
kayak ] A kayak is a small, narrow human-powered watercraft typically propelled by means of a long, double-bladed paddle. The word ''kayak'' originates from the Inuktitut word '' qajaq'' (). In British English, the kayak is also considered to be ...
s,
cricket bat A cricket bat is a specialised piece of equipment used by batters in the sport of cricket to hit the ball, typically consisting of a cane handle attached to a flat-fronted willow-wood blade. It may also be used by a batter who is making batte ...
s, and
field hockey Field hockey (or simply referred to as hockey in some countries where ice hockey is not popular) is a team sport structured in standard hockey format, in which each team plays with 11 players in total, made up of 10 field players and a goalk ...
,
ice hockey Ice hockey (or simply hockey in North America) is a team sport played on ice skates, usually on an Ice rink, ice skating rink with Ice hockey rink, lines and markings specific to the sport. It belongs to a family of sports called hockey. Tw ...
and
lacrosse Lacrosse is a contact team sport played with a lacrosse stick and a lacrosse ball. It is the oldest organized sport in North America, with its origins with the indigenous people of North America as early as the 12th century. The game w ...
sticks. Kevlar 149, the strongest fiber and most crystalline in structure, is an alternative in certain parts of aircraft construction. The wing leading edge is one application, Kevlar being less prone than carbon or glass fiber to break in bird collisions.


See also

*
Innegra S Innegra S is the brandname of Innegra Technologies LLC for a polyolefin (highly oriented; 90+% polypropylene). History Work on Innegra began in 2004. A pilot production line was opened in Greer, SC in June 2006 On July 11, 2006 the US Paten ...
*
Ultra-high-molecular-weight polyethylene Ultra-high-molecular-weight polyethylene (UHMWPE, UHMW) is a subset of the thermoplastic polyethylene. Also known as high-modulus polyethylene (HMPE), it has extremely long chains, with a molecular mass typically between 2 and 6 million amu. The l ...
*
Twaron Twaron (a brand name of Teijin Aramid) is a para-aramid, high-performance yarn. It is a heat-resistant fibre, helps in ballistic protection and cut protection. Twaron was developed in the early 1970s by the Dutch company Akzo Nobel's division E ...
*
Vectran Vectran is a manufactured fiber, spun from a liquid-crystal polymer (LCP) created by Celanese Corporation and now manufactured by Kuraray. Chemically it is an aromatic polyester produced by the polycondensation of 4-hydroxybenzoic acid and 6 ...


References


External links

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Aramids

Matweb material properties of Kevlar
*


Kevlar in body armor



Aberfeldy Footbridge over the River Tay

Kevlar
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