Kevlar is the registered trademark for a light, strong para-aramid synthetic fiber, related to other aramids such as Nomex and Technora. A trademark or trade mark, represented by the symbols ™ and ®, or mark is a distinctive sign or indicator used by an individual Aramid fibers are a class of heat-resistant and strong Synthetic fibers They are used in aerospace and military applications for ballistic rated body armor Synthetic fibers are the result of extensive research by Scientists to improve upon naturally occurring Animal and plant Aramid fibers are a class of heat-resistant and strong Synthetic fibers They are used in aerospace and military applications for ballistic rated body armor Nomex (styled NOMEX) is a registered Trademark for flame resistant meta- Aramid material developed in the early 1960s by DuPont and first marketed Technora is the brandname of Teijin for a aromatic copolyamid.

Developed at DuPont in 1965 by Stephanie Kwolek and Roberto Berendt,^[1] it was first commercially used in the early 1970s. E I du Pont de Nemours and Company (,) is an American chemical company that was founded in July 1802 as a Gunpowder mill by Eleuthère Irénée Stephanie Kwolek (born July 31, 1923) is an American Chemist who discovered poly-paraphenylene terephtalamide&mdashbetter known as Kevlar Typically it is spun into ropes or fabric sheets that can be used as such or as an ingredient in composite material components. A textile is a flexible material comprised of a network of natural or artificial Fibres often referred to as thread or Yarn. Composite materials (or composites for short are engineered Materials made from two or more constituent materials with significantly different physical or chemical

Currently, Kevlar has many applications, ranging from bicycle tires and racing sails to body armor because of its high strength-to-weight ratio—famously: ". This article is about tires used on road Vehicles including pneumatic tires and solid tires. Sails have been made from Cloth for all of recorded history Typically sails were made from Flax ( Linen) Hemp or Cotton in various A ballistic vest is an item of protective clothing that absorbs the impact from gun-fired Projectiles and shrapnel fragments from explosion . . 5 times stronger than steel on an equal weight basis. . . "^[1]

A similar fiber called Twaron with roughly the same chemical structure was introduced by Akzo in 1978, and now manufactured by Teijin. Twaron is the brandname of Teijin Aramid for a para-aramid. History Twaron is a heat-resistant and strong Synthetic fiber developed Akzo Nobel NV, trading as AkzoNobel, is a multinational company active in the fields of decorative Paints performance Coatings and specialty Chemicals ( is a Japanese chemical and pharmaceutical company It is listed on the Tokyo Stock Exchange with a market capitalisation of USD 3

Contents 1 History 2 Properties 3 Production 4 Chemical properties 5 Thermal properties 6 Applications 6.1 Armor 6.2 Rope and cable 6.3 Sports equipment 6.4 Audio equipment 6.5 Electricity generation 6.6 Drumheads 6.7 Fiber Optic Cable 6.8 Building construction 6.9 Brakes 7 Composite materials 8 See also 9 Notes 10 References 11 External links

History

In the 1970s, one of its most significant achievements in the development of body armor was the invention of DuPont's Kevlar ballistic fabric. The fabric was originally intended to replace steel belting in vehicle tires. The development of Kevlar body armor by NIJ was a four-phase effort that took place over several years. The first phase involved testing Kevlar fabric to determine whether it could stop a lead bullet. The second phase involved determining the number of layers of material necessary to prevent penetration by bullets of varying speeds and calibers and developing a prototype vest that would protect officers against the most common threats: the 38 Special and the 22 Long Rifle bullets. By 1973, researchers at the Army's Edgewood Arsenal responsible for the bullet proof vest design had developed a garment made of seven layers of Kevlar fabric for use in field trials. It was determined that the penetration resistance of Kevlar was degraded when wet. The bullet resistant properties of the fabric also diminished upon exposure to ultraviolet light, including sunlight. Dry-cleaning agents and bleach also had a negative effect on the antiballistic properties of the fabric, as did repeated washing. To protect against these problems, the vest was designed with waterproofing, as well as with fabric coverings to prevent exposure to sunlight and other degrading agents.

Properties

When Kevlar is spun, the resulting fiber has great tensile strength (ca. A spinneret is a spider's silk -spinning organ. It is usually on the underside of a spider's Abdomen, to the rear Tensile strength \sigma_{UTS} or S_U is the Stress at which a material breaks or permanently deforms 3 000 MPa), and a relative density of 1. Relative density, sometimes called specific density, is the Ratio of the Density of a substance to the density of a given reference material 44. When used as a woven material, it is suitable for mooring lines and other underwater application objects.

There are three grades of Kevlar: (i) Kevlar, (ii) Kevlar 29, and (iii) Kevlar 49. Typically, Kevlar is used as reinforcement in tires and rubber mechanical goods. Kevlar 29's industrial applications are as cables, in asbestos replacement, brake linings, and body armor. Asbestos is a group of Minerals with long thin fibrous Crystals The word "asbestos" (῾ἀσβεστος is derived from a Greek adjective Kevlar 49 has the greatest tensile strength of all the aramids, and is used in plastic reinforcement for boat hulls, airplanes, and bicycles. The ultraviolet light component of sunlight degrades and decomposes Kevlar, a problem known as UV degradation, and so it is rarely used outdoors without protection against sunlight. Ultraviolet ( UV) light is Electromagnetic radiation with a Wavelength shorter than that of Visible light, but longer than X-rays Many natural and synthetic Polymers are attacked by Ultra-violet radiation and products made using these materials may crack or disintegrate

Production

Kevlar is synthesised from the monomers 1,4-phenylene-diamine (para-phenylenediamine) and terephthaloyl chloride in condensation reaction yielding hydrochloric acid as a byproduct. A monomer (from Greek mono "one" and meros "part" is a small Molecule that may become chemically bonded to other The phenylene group is based on a di-substituted Benzene ring Amines are Organic compounds and Functional groups that contain a basic Nitrogen Atom with a Lone pair. p -Phenylenediamine ( PPD) also called paraphenylenediamine 14-diaminobenzene or 14- Phenylenediamine is an Aromatic Amine used Terephthaloyl chloride ( TCL, 14-benzenedicarbonyl chloride) is the acid chloride of Terephthalic acid and is one of two Monomers used to Condensation polymers are any class of Polymers formed through a Condensation reaction, releasing a small molecule by-product such as water or methanol as opposed Hydrochloric acid is the Solution of Hydrogen chloride ( H[[Chlorine Cl]] in water The result is a liquid-crystalline behaviour and mechanical drawing orienting the polymer chains in the fiber's direction. Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional Liquid, and those of a Solid Hexamethylphosphoramide (HMPA) was the polymerization solvent first used, but toxicology tests demonstrated it provoked tumors in the noses of rats, so DuPont replaced it by a N-methyl-pyrrolidone and calcium chloride as the solvent. Hexamethylphosphoramide (abbreviated HMPA is a colorless organic liquid with the formula 3PO As this process was patented by Akzo (see above) in the production of Twaron, a patent war ensued.

Kevlar (poly paraphenylene terephthalamide) production is expensive because of the difficulties arising from using corrosive concentrated sulfuric acid, needed to keep the water-insoluble polymer in solution during its synthesis and spinning. Sulfuric (or sulphuric acid, H 2 S[[oxygen O]]4 is a strong Mineral acid. Spinning is an ancient textile art in which plant, animal or synthetic Fibers are twisted together to form Yarn (or thread

Chemical properties

Fibers of Kevlar consist of long molecular chains produced from PPTA (poly-paraphenylene terephthalamide). There are many inter-chain bonds making the material extremely strong. Kevlar derives part of its high strength from inter-molecular hydrogen bonds formed between the carbonyl groups and protons on neighboring polymer chains and the partial pi stacking of the benzenoid aromatic stacking interactions between stacked strands. A hydrogen bond results from a Dipole-dipole force between an Electronegative atom and a Hydrogen atom bonded to Nitrogen, Oxygen Stacking in Supramolecular chemistry refers to a stacked arrangement of Aromatic Molecules which interact through aromatic interactions 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 Dyneema. The Van der Waals equation is an Equation of state that can be derived from a special form of the potential between a pair of molecules (hard-sphere repulsion Ultra high molecular weight polyethylene ( UHMWPE) also known as high-modulus polyethylene ( HMPE) or high-performance polyethylene ( HPPE The presence of salts and certain other impurities, especially calcium, could interfere with the strand interactions and caution is used to avoid inclusion in its production. Salt is a Dietary mineral composed primarily of Sodium chloride that is essential for Animal life but toxic to most land plants Calcium (ˈkælsiəm is the Chemical element with the symbol Ca and Atomic number 20 Kevlar's structure consists of relatively rigid molecules which tend to form mostly planar sheet-like structures rather like silk protein. Silk is a natural Protein Fiber, some forms of which can be woven into Textiles The best-known type of silk is obtained from cocoons

Thermal properties

For a polymer Kevlar has very good resistance to high temperatures, and maintains its strength and resilience down to cryogenic temperatures (-196°C); indeed, 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 at 160°C about 10% reduction in strength occurs after 500 hours. At 260°C 50% reduction occurs after 70 hours. ^[2]

At 450°C Kevlar sublimates. Sublimation of an element or compound is a transition from the Solid to Gas phase with no intermediate liquid stage

Applications

Armor

Kevlar is well-known as a component of some bulletproof vests and bulletproof facemasks. A ballistic vest is an item of protective clothing that absorbs the impact from gun-fired Projectiles and shrapnel fragments from explosion The PASGT helmet and vest used by US military forces since the early 1980s both have Kevlar as a key component, as do their replacements. Personnel Armor System for Ground Troops, sometimes abbreviated to PASGT, is a Combat helmet and ballistic vest used by the American military from the late 1980s The United States of America —commonly referred to as the Other military uses include bulletproof facemasks used by sentries. Civilian applications include Kevlar reinforced clothing for motorcycle riders to protect against abrasion injuries and also Emergency Service's protection gear if it involves high heat (e. g. , tackling a fire), and Kevlar body armor such as vests for Police officers, security, and S. W. A. T.

Rope and cable

The fiber is used in woven rope and in cable, where the fibers are kept parallel within a polyethylene sleeve. Polyethylene or polythene ( IUPAC name poly(ethene) is a Thermoplastic commodity heavily used in consumer products (notably the Known as "Parafil", the cables have been used in small suspension bridges such as the bridge at Aberfeldy in Scotland. This article is concerned with a particular type of suspension bridge the suspended-deck type Scotland ( Gaelic: Alba) is a Country in northwest Europethat occupies the northern third of the island of Great Britain. They have also been used to stabilise cracking concrete cooling towers by circumferential application followed by tensioning to close the cracks.

Sports equipment

In many cases it is part of a composite material, used in the production of some tennis, table tennis, badminton and squash rackets, kayaks, some cricket bats and some field hockey and lacrosse sticks. Composite materials (or composites for short are engineered Materials made from two or more constituent materials with significantly different physical or chemical It is used as an inner lining for some bicycle tires to prevent punctures, and due to its excellent heat resistance, is used for fire poi wicks. Poi is a form of Juggling or Object manipulation employing a ball depending from a length of rope which is held in hand and swung in circular patterns comparable It is used for Motorcycle safety clothing, especially in the areas featuring padding such as shoulders and elbows. To improve Motorcycle safety many countries mandate the wearing of Protective clothing by motorcyclists especially It was also used as speed control patches for certain soap shoes models. Soap Shoes are Shoes made for grinding. They were introduced by Chris Morris of Artemis Innovations Inc In Kyudo or Japanese archery, it may be used as an alternative to more expensive hemp for bow strings. literally meaning " way of the bow " is the Japanese art of Archery. It is one of the main materials used for paraglider suspension lines. Paragliding is a recreational and competitive flying sport A paraglider is a free-flying foot-launched Aircraft.

Audio equipment

It has also been found to have useful acoustic properties for loudspeaker cones, specifically for bass and midrange drive units^[3].

Electricity generation

It was used by scientists from Georgia Tech as a base textile for an experiment in electricity-producing clothing. This was done by weaving zinc-oxide nanowires into the fabric. If successful, the new fabric would generate about 80 miliwatts per square meter. ^[4]

Drumheads

Kevlar is sometimes used as a material in high tension drum heads usually used on marching snare drums. It supposedly gives a higher pitch sound and allows for an extremely high amount of tension. There is usually some sort of resin poured onto the kevlar to prevent the air inside the drum from escaping through the head. This is one of the primary types of marching snare drum heads. Remo's falam slam patch is made with kevlar and is stuck to bass drum heads where the beater strikes to strengthen the head so it doesn't wear down as quickly. Remo is an American Drumhead company They are well known for their highly successful Weatherking series which is now seen on orchestral world and marching

Fiber Optic Cable

Kevlar is widely used as a protective outer sheath for fiber optic cable, as its strength protects the cable from damage and kinking. An optical fiber cable is a Cable containing one or more Optical fibers The optical fiber elements are typically individually coated with plastic layers and contained

Building construction

A retractable roof of over 60,000 square feet (5,575 square metres) of Kevlar was a key part of the design of Montreal's Olympic stadium for the 1976 Summer Olympics. The Olympic Stadium (Stade olympique is a Multi-purpose stadium in Montreal, Quebec, Canada built as the main venue for the 1976 The 1976 Summer Olympics, officially known as the Games of the XXI Olympiad, were an International Multi-sport event held in Montreal, Quebec It was spectacularly unsuccessful: completed ten years late and replaced ten years later in May 1998 after a series of problems. ^[5][6]

Brakes

The chopped fiber has been used as a replacement for asbestos in brake pads. Asbestos is a group of Minerals with long thin fibrous Crystals The word "asbestos" (῾ἀσβεστος is derived from a Greek adjective Brake pads are an important part of braking systems for all types of vehicles that are equipped with Disc brakes Brake pads are steel backing plates with friction Dust produced from asbestos brakes is toxic, while aramids are a benign substitute.

Composite materials

Aramid fibers are widely used for reinforcing composite materials, often in combination with carbon fiber and glass fiber. Composite materials (or composites for short are engineered Materials made from two or more constituent materials with significantly different physical or chemical Fiberglass (also called fibreglass and glass fibre see Spelling differences) is material made from extremely fine Fibers of Glass. The matrix for high performance composites is usually epoxy resin. In Chemistry, epoxy or polyepoxide is a Thermosetting Epoxide Polymer that cures (polymerizes and crosslinks when mixed with a Typical applications include monocoque bodies for F1 racing cars, and helicopter rotor blades. Monocoque, from the French for single ( mono) and shell ( coque) is a construction technique that supports structural load by using an object's external Auto racing (also known as automobile racing, motor racing or car racing) is a Motorsport involving Racing Cars It History Since 400 AD Chinese children have played with bamboo flying toys.

See also

• Aramid
• Bulletproof vest
• DuPont (Company that invented and manufactures Kevlar)
• Interceptor body armor
• Nomex
• Personnel Armor System for Ground Troops
• Spider silk
• Twaron
• Ultra high molecular weight polyethylene
• UV degradation
• Soap Shoes
• Fire dancing

Notes

References

• Kadolph, Sara J. Structurae is an online Database containing works of structural and Civil engineering of all kinds such as Bridges High-rise buildings Anna L. Langford. Textiles, Ninth Edition. Pearson Education, Inc 2002. Upper Saddle River, NJ
• D. Tanner, J. A. Fitzgerald, B. R. Phillips (1989). "The Kevlar Story - an Advanced Materials Case Study". Angewandte Chemie International Edition in English 28 (5): 649 - 654. Angewandte Chemie is a weekly Peer-reviewed Chemistry journal that covers all disciplines of chemistry doi:10.1002/anie.198906491. A digital object identifier ( DOI) is a permanent identifier given to an Electronic document.  
• E. E. Magat (1980). "Fibers from Extended Chain Aromatic Polyamides, New Fibers and Their Composites". Philosophical Transactions of the Royal Society of London Series A 294 (1411): 463-472.  
• Ronald V. Joven. Manufacturing Kevlar panels by thermo-curing process. Los Andes University, 2007. Bogotá, Colombia.

External links

• Kevlar Home Page
• Aramids
• Kevlar - Design Dictionary. Illustrated article about Kevlar
• Matweb material properties of Kevlar
• U.S. Patent 5,565,264 
• Kevlar
• Synthesis of Kevlar
• Aberfeldy Footbridge over the River Tay

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