kevlar - wikipedia, the free encyclopedia
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Kelvar from WikiTRANSCRIPT
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Kevlar
Identifiers
CAS number 24938-64-5
Properties
Molecular formula [-CO-C6H4-CO-NH-C6H4-NH-
]n
Except where noted otherwise, data are given formaterials in their standard state (at 25 °C (77 °F),100 kPa)
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Infobox references
KevlarFrom Wikipedia, the free encyclopedia
Kevlar is the registered trademark for a para-aramidsynthetic fiber, related to other aramids such as Nomexand Technora. Developed by Stephanie Kwolek atDuPont in 1965,[1][2][3] this high-strength material wasfirst commercially used in the early 1970s as areplacement for steel in racing tires. Typically it is spuninto ropes or fabric sheets that can be used as such or asan ingredient in composite material components.
Currently, Kevlar has many applications, ranging frombicycle tires and racing sails to body armor because of itshigh tensile strength-to-weight ratio; by this measure it is5 times stronger than steel.[2] It is also used to makemodern drumheads that withstand high impact. Whenused as a woven material, it is suitable for mooring linesand other underwater applications.
A similar fiber called Twaron with roughly the samechemical structure was developed by Akzo in the 1970s;commercial production started in 1986, and Twaron isnow manufactured by Teijin.[4][5]
Contents
1 History2 Production3 Structure and properties4 Thermal properties5 Applications
5.1 Protection5.1.1 Cryogenics5.1.2 Armor5.1.3 Personal protection
5.2 Sports equipment5.2.1 Shoes
5.3 Music5.3.1 Audio equipment
5.3.2 Bowed string instruments
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Stephanie Kwolek, an Americanchemist of Polish origin, inventor ofkevlar
5.3.2 Bowed string instruments5.3.3 Drumheads5.3.4 Woodwind reeds
5.4 Other uses5.4.1 Fire dancing5.4.2 Frying pans5.4.3 Rope, cable, sheath5.4.4 Electricity generation5.4.5 Building construction5.4.6 Brakes5.4.7 Expansion joints and hoses5.4.8 Particle physics5.4.9 Smartphones5.4.10 Marine Current Turbine andWind turbine
6 Composite materials7 See also8 References9 External links
History
Poly-paraphenylene terephthalamide – branded Kevlar – wasinvented by Polish-American chemist Stephanie Kwolek whileworking for DuPont,[6] in anticipation of a gasoline shortage. In1964, her group began searching for a new lightweight strong fiberto use for light but strong tires.[6] The polymers she had beenworking with at the time, poly-p-Phenylene-terephthalate andpolybenzamide,[7] formed liquid crystal while in solution, somethingunique to those polymers at the time.[6]
The solution was "cloudy, opalescent upon being stirred, and of lowviscosity" and usually was thrown away. However, Kwolekpersuaded the technician, Charles Smullen, who ran the "spinneret",to test her solution, and was amazed to find that the fiber did notbreak, unlike nylon. Her supervisor and her laboratory directorunderstood the significance of her accidental discovery and a newfield of polymer chemistry quickly arose. By 1971, modern Kevlar was introduced.[6] However, Kwolekwas not very involved in developing the applications of Kevlar.[8]
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Production
Kevlar is synthesized in solution from the monomers 1,4-phenylene-diamine (para-phenylenediamine) andterephthaloyl chloride in a condensation reaction yielding hydrochloric acid as a byproduct. The result hasliquid-crystalline behavior, and mechanical drawing orients the polymer chains in the fiber's direction.Hexamethylphosphoramide (HMPA) was the solvent initially used for the polymerization, but for safetyreasons, DuPont replaced it by a solution of N-methyl-pyrrolidone and calcium chloride. As this processhad been patented by Akzo (see above) in the production of Twaron, a patent war ensued.[9]
The reaction of 1,4-phenylene-diamine (para-phenylenediamine) with terephthaloyl chlorideyielding kevlar
Kevlar (poly paraphenylene terephthalamide) production is expensive because of the difficulties arisingfrom using concentrated sulfuric acid, needed to keep the water-insoluble polymer in solution during itssynthesis and spinning.
Several grades of Kevlar are available:
1. Kevlar K-29 – in industrial applications, such as cables, asbestos replacement, brake linings, andbody/vehicle armor.
2. Kevlar K49 – high modulus used in cable and rope products.3. Kevlar K100 – colored version of Kevlar4. Kevlar K119 – higher-elongation, flexible and more fatigue resistant5. Kevlar K129 – higher tenacity for ballistic applications
6. Kevlar AP – 15% higher tensile strength than K-29[10]
7. Kevlar XP – lighter weight resin and KM2 plus fiber combination[11]
8. Kevlar KM2 – enhanced ballistic resistance for armor applications[12]
The ultraviolet component of sunlight degrades and decomposes Kevlar, a problem known as UVdegradation, and so it is rarely used outdoors without protection against sunlight.
Structure and properties
When Kevlar is spun, the resulting fiber has a tensile strength of about 3,620 MPa,[13] and a relative densityof 1.44. The polymer owes its high strength to the many inter-chain bonds. These inter-molecular hydrogenbonds form between the carbonyl groups and NH centers. Additional strength is derived from aromatic
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Molecular structure of Kevlar: bold represents a monomer unit,dashed lines indicate hydrogen bonds.
Pieces of Kevlar helmet used to helpabsorb the blast of a grenade
stacking interactions between adjacent strands. These interactions have a greater influence on Kevlar thanthe van der Waals interactions and chain length that typically influence the properties of other syntheticpolymers and fibers such as Dyneema. The presence of salts and certain other impurities, especiallycalcium, could interfere with the strandinteractions and care is taken to avoidinclusion in its production. Kevlar'sstructure consists of relatively rigidmolecules which tend to form mostlyplanar sheet-like structures rather likesilk protein.[14]
Thermal properties
Kevlar maintains its strength andresilience down to cryogenictemperatures (−196 °C); in fact, it isslightly stronger at low temperatures. Athigher temperatures the tensile strength is immediately reduced by about 10–20%, and after some hours thestrength progressively reduces further. For example at 160 °C (320 °F) about 10% reduction in strengthoccurs after 500 hours. At 260 °C (500 °F) 50% strength reduction occurs after 70 hours.[15]
Applications
Protection
Cryogenics
Kevlar is often used in the field of cryogenics for its low thermal conductivity and high strength relative toother materials for suspension purposes. It is most often used to suspend a paramagnetic salt enclosure froma superconducting magnet mandrel in order to minimize any heat leaks to the paramagnetic material. It isalso used as a thermal standoff or structural support where low heat leaks are desired.
Armor
Kevlar is a well-known component of personal armor such ascombat helmets, ballistic face masks, and ballistic vests. ThePASGT helmet and vest used by United States military forces sincethe 1980s both have Kevlar as a key component, as do theirreplacements. Other military uses include bulletproof facemasksused by sentries and spall liners used to protect the crews ofarmoured fighting vehicles. Even Nimitz-class aircraft carriersinclude Kevlar armor around vital spaces. Related civilianapplications include Emergency Service's protection gear if itinvolves high heat (e.g., tackling a fire), and Kevlar body armorsuch as vests for police officers, security, and SWAT.[16]
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Kevlar is a very popular material forracing canoes.
Personal protection
Kevlar is used to manufacture gloves, sleeves, jackets, chaps and other articles of clothing[17] designed toprotect users from cuts, abrasions and heat. Kevlar based protective gear is often considerably lighter andthinner than equivalent gear made of more traditional materials.[16]
Sports equipment
It is used as an inner lining for some bicycle tires to preventpunctures. In table tennis, plies of Kevlar are added to custom plyblades, or paddles, in order to increase bounce and reduce weight. Itis used for motorcycle safety clothing, especially in the areasfeaturing padding such as shoulders and elbows.
In kyudo or Japanese archery, it may be used as an alternative tomore expensive hemp for bow strings. It is one of the main materialsused for paraglider suspension lines.[18]
In fencing it is used in the protective jackets, breeches, plastrons andthe bib of the masks.
Tennis racquets are often strung with Kevlar.
It is even used in sails for high performance racing boats.
It is increasingly being used in the "peto", the padded covering which protects the picadors' horses in thebullring.
Shoes
With advancements in technology, Nike used Kevlar in shoes for the first time. It launched the Elite IISeries (http://nikeinc.com/news/nike-basketball-s-superhero-elite-series-2-0-rises-above-the-rest), withenhancements to its earlier version of basketball shoes by using Kevlar in the anterior as well as the shoelaces. This was done to decrease the elasticity of the tip of the shoe in contrast to nylon used conventionallyas Kevlar expanded by about 1% against nylon which expanded by about 30%. Shoes in this range includedLeBron, HyperDunk and Zoom Kobe VII. However these shoes were launched at a price range muchhigher than average cost of basketball shoes.
It was also used as speed control patches for certain Soap Shoes models. and the laces for the adidas F50adiZero Prime football boot.
Music
Audio equipment
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Fire poi on a beach in San Francisco
Kevlar has also been found to have useful acoustic properties for loudspeaker cones, specifically for bassand midrange drive units.[19] Additionally, Kevlar has been used as a strength member in fiber optic cablessuch as the ones used for audio data transmissions.[20]
Bowed string instruments
Kevlar can be used as an acoustic core on bows for string instruments.[21] Kevlar's physical propertiesprovide strength, flexibility, and stability for the bow's user. To date, the only manufacturer of this type ofbow is CodaBow.[22]
Kevlar is also presently used as a material for tailcords (aka tailpiece adjusters), which connect the tailpieceto the endpin of bowed string instruments.[23]
Drumheads
Kevlar is sometimes used as a material on marching snare drums. It allows for an extremely high amount oftension, resulting in a cleaner sound. There is usually a resin poured onto the Kevlar to make the headairtight, and a nylon top layer to provide a flat striking surface. This is one of the primary types of marchingsnare drum heads. Remo's "Falam Slam" Patch is made with Kevlar and is used to reinforce bass drumheads where the beater strikes.
Woodwind reeds
Kevlar is used in the woodwind reeds of Fibracell. The material of these reeds is a composite of aerospacematerials designed to duplicate the way nature constructs cane reed. Very stiff but sound absorbing Kevlarfibers are suspended in a lightweight resin formulation.[24]
Other uses
Fire dancing
Wicks for fire dancing props are made of composite materials withKevlar in them. Kevlar by itself does not absorb fuel very well, so itis blended with other materials such as fiberglass or cotton. Kevlar'shigh heat resistance allows the wicks to be reused many times.
Frying pans
Kevlar is sometimes used as a substitute for Teflon in some non-stick frying pans.[25]
Rope, cable, sheath
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Kevlar mooring line
The fiber is used in woven rope and in cable, where the fibers are kept parallel within a polyethylene sleeve.The cables have been used in suspension bridges such as the bridge at Aberfeldy in Scotland. They havealso been used to stabilize cracking concrete cooling towers bycircumferential application followed by tensioning to close thecracks. Kevlar is widely used as a protective outer sheath for opticalfiber cable, as its strength protects the cable from damage andkinking. When used in this application it is commonly known by thetrademarked name Parafil.
Electricity generation
Kevlar was used by scientists at Georgia Institute of Technology asa base textile for an experiment in electricity-producing clothing.This was done by weaving zinc oxide nanowires into the fabric. Ifsuccessful, the new fabric would generate about 80 milliwatts per square meter.[26]
Building construction
A retractable roof of over 60,000 square feet (5,575 square metres) of Kevlar was a key part of the designof Montreal's Olympic stadium for the 1976 Summer Olympics. It was spectacularly unsuccessful, as it wascompleted ten years late and replaced just ten years later in May 1998 after a series of problems.[27][28]
Brakes
The chopped fiber has been used as a replacement for asbestos in brake pads. Dust produced from asbestosbrakes is toxic, while aramids are a benign substitute.
Expansion joints and hoses
Kevlar can be found as a reinforcing layer in rubber bellows expansion joints and rubber hoses, for use inhigh temperature applications, and for its high strength. It is also found as a braid layer used on the outsideof hose assemblies, to add protection against sharp objects.
Particle physics
A thin Kevlar window has been used by the NA48 experiment at CERN to separate a vacuum vessel from avessel at nearly atmospheric pressure, both 192 cm in diameter. The window has provided vacuum tightnesscombined with reasonably small amount of material (only 0.3% to 0.4% of radiation length).
Smartphones
The Motorola RAZR Family and the Motorola Droid Maxx have a kevlar backplate, chosen over othermaterials such as carbon fiber due to its resilience and lack of interference with signal transmission.[29]
Marine Current Turbine and Wind turbine
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The Kevlar fiber/epoxy matrix composite materials can be used in marine current turbine (MCT) or windturbine due to their high specific strength and light weight compared to other fibers.[30]
Composite materials
Aramid fibers are widely used for reinforcing composite materials, often in combination with carbon fiberand glass fiber. The matrix for high performance composites is usually epoxy resin. Typical applicationsinclude monocoque bodies for F1 racing cars, helicopter rotor blades, tennis, table tennis, badminton andsquash rackets, kayaks, cricket bats, and field hockey, ice hockey and lacrosse sticks.[31][32][33][34]
See also
Innegra SVectranSpider silkUltra high molecular weight polyethylene
References
1. ^ Stephanie Kwolek, Hiroshi Mera and Tadahiko Takata “High-Performance Fibers” in Ullmann's Encyclopediaof Industrial Chemistry 2002, Wiley-VCH, Weinheim. doi:10.1002/14356007.a13_001(http://dx.doi.org/10.1002%2F14356007.a13_001)
2. ^ a b "What is Kevlar" (http://www.dupont.com/kevlar/whatiskevlar.html). DuPont. Retrieved 2007-03-28.3. ^ Wholly Aromatic Carbocyclic Polycarbonamide Fiber (http://ip.com/pat/US3819587) Original Kevlar patent
awarded in 1974 to Stephanie Kwolek4. ^ Tatsuya Hongū, Glyn O. Phillips, New Fibers, Ellis Horwood, 1990, p. 225. ^ J. K. Fink, Handbook of Engineering and Specialty Thermoplastics: Polyolefins and Styrenics, Scrivener
Publishing, 2010, p. 35
6. ^ a b c d "Inventing Modern America: Insight — Stephanie Kwolek:" (http://www.webcitation.org/query?url=http%3A%2F%2Fweb.mit.edu%2Finvent%2Fwww%2Fima%2Fkwolek_bio.html&date=2009-05-24).Lemelson-MIT program. Archived from the original (http://web.mit.edu/invent/www/ima/kwolek_bio.html) onMay 24, 2009. Retrieved May 24, 2009.
7. ^ "World of Invention Biography" (http://www.webcitation.org/query?url=http%3A%2F%2Fwww.bookrags.com%2Fbiography%2Fstephanie-louise-kwolek-woi%2F&date=2009-05-24). Bookrags. Archived from the original (http://www.bookrags.com/biography/stephanie-louise-kwolek-woi/)on May 24, 2009. Retrieved May 24, 2009.
8. ^ Quinn, Jim. "I was able to be Creative and work as hard as I wanted" (http://www.webcitation.org/query?url=http%3A%2F%2Fwww.americanheritage.com%2Farticles%2Fmagazine%2Fit%2F2003%2F3%2F2003_3_60.shtml&date=2009-05-24). American Heritage Publishing. Archived from the original(http://www.americanheritage.com/articles/magazine/it/2003/3/2003_3_60.shtml) on May 24, 2009. RetrievedMay 24, 2009.
9. ^ How Kevlar® works: a simple introduction (http://www.explainthatstuff.com/kevlar.html).
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9. ^ How Kevlar® works: a simple introduction (http://www.explainthatstuff.com/kevlar.html).Explainthatstuff.com (2009-12-07). Retrieved on 2012-05-26.
10. ^ Kevlar K-29 AP Technical Data Sheet(http://www2.dupont.com/Kevlar/en_US/assets/downloads/K23339_KevlarAP.pdf) – Dupont
11. ^ Kevlar XP (http://www2.dupont.com/Kevlar/en_US/products/life_protection/kevlarxp_dupont.html) – Dupont12. ^ Kevlar KM2 Technical Description
(http://www2.dupont.com/Kevlar/en_US/products/life_protection/kevlar_km2.html). dupont.com. Retrieved on2012-05-26.
13. ^ Quintanilla, J. (1990). "Microstructure and properties of random heterogeneous materials : a review oftheoretical results". Polymer engineering and science 39: 559–585.
14. ^ Michael C. Petty, Molecular electronics: from principles to practice, John Wiley & Sons, 2007, p. 31015. ^ KEVLAR Technical Guide
(http://www2.dupont.com/Kevlar/en_US/assets/downloads/KEVLAR_Technical_Guide.pdf). dupont.com.Retrieved on 2012-05-26.
16. ^ a b Body Armor Made with Kevlar(http://www2.dupont.com/Kevlar/en_US/uses_apps/body_armor/index.html). (2005-0604). DuPont the Miraclesof Science. Retrieved November 4, 2011
17. ^ Kevlar – DuPont Personal Protection(http://www2.dupont.com/Personal_Protection/en_US/products/kevlar/index.html). .dupont.com. Retrieved on2012-05-26.
18. ^ Pagen, Dennis (1990), Paragliding Flight: Walking on Air, Pagen Books (http://www.pagenbooks.com), p. 9,ISBN 0-936310-09-X
19. ^ Audio speaker use (http://www.audioholics.com/reviews/speakers/bookshelf/bw-cm1/cm1-design-and-construction). Audioholics.com (2009-07-23). Retrieved on 2012-05-26.
20. ^ Welcome to Kevlar (http://www2.dupont.com/Kevlar/en_US/index.html). (2005-06-04). DuPont the Miraclesof Science. Retrieved November 4, 2011
21. ^ carbon fiber bows for violin, viola, cello and bass (http://www.codabow.com/violin_sx.html). CodaBow.Retrieved on 2012-05-26.
22. ^ carbon fiber bows for violin, viola, cello and bass (http://www.codabow.com/insidecb_h1.html). CodaBow.Retrieved on 2012-05-26.
23. ^ Tailpieces and Tailcords (http://www.aitchisoncellos.com/articletailpieces.htm) Aitchison Mnatzaganian cellomakers, restorers and dealers. Retrieved on 2012-12-17.
24. ^ "FibraCell Website" (http://www.fibracelldirect.com/).25. ^ M.Rubinstein, R.H.Colby, Polymer Physics, Oxford University Press, p33726. ^ Fabric Produces Electricity As You Wear It (http://www.sciam.com/podcast/episode.cfm?id=3E0E600F-F7B2-
4F1F-DA377027B8FDC443&sc=rss). Scientific American (2008-02-22). Retrieved on 2012-05-26.27. ^ Roof of the Montreal Olympic Stadium (http://en.structurae.de/structures/data/index.cfm?ID=s0000742) at
Structurae28. ^ Clem's Baseball ~ Olympic Stadium (http://www.andrewclem.com/Baseball/OlympicStadium.html).
Andrewclem.com. Retrieved on 2012-05-26.29. ^ Droid RAZR (http://www.motorola.com/Consumers/US-EN/Consumer-Product-and-Services/Mobile-
Phones/DROID-RAZR-BY-MOTOROLA-US-EN). (2011-10-11). Motorola Mobility. Retrieved November 4,
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Wikimedia Commons hasmedia related to Kevlar.
Wikimedia Commons hasmedia related to Aramid.
External links
Kevlar Home Page (http://www.kevlar.com/)Aramids (http://www.pslc.ws/macrog/aramid.htm)Kevlar – Design Dictionary. Illustrated article about Kevlar(http://www.designdictionary.co.uk/en/kevlar.htm)Matweb material properties of Kevlar(http://www.matweb.com/search/SpecificMaterial.asp?bassnum=PDUKEV29)U.S. Patent 5,565,264 (https://www.google.com/patents/US5565264)Kevlar (http://www.lbl.gov/MicroWorlds/Kevlar/index.html)Kevlar in body armor (http://www.bodyarmornews.com/bullet-proof-vest/)Synthesis of Kevlar (http://web.mst.edu/~wlf/Synthesis/kevlar.html)Aberfeldy Footbridge over the River Tay(http://www.ngcc.org.uk/DesktopModules/ViewDocument.aspx?DocumentID=1003)Kevlar (http://plastics.inwiki.org/Kevlar) at Plastics Wiki
Retrieved from "http://en.wikipedia.org/w/index.php?title=Kevlar&oldid=623556270"
Categories: Organic polymers Personal armour DuPont Synthetic fibers Technical fabricsBrand name materials 1965 introductions DuPont products
This page was last modified on 31 August 2014 at 09:47.Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may
201130. ^ Wang, Jifeng; Norbert Müller (December 2011). "Numerical investigation on composite material marine
current turbine using CFD" (http://link.springer.com/article/10.2478%2Fs13531-011-0033-6?LI=true#). CentralEuropean Journal of Engineering 1 (4): 334–340. Retrieved 26 December 2012.
31. ^ Kadolph, Sara J. Anna L. Langford. Textiles, Ninth Edition. Pearson Education, Inc 2002. Upper Saddle River,NJ
32. ^ 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. doi:10.1002/anie.198906491(http://dx.doi.org/10.1002%2Fanie.198906491).
33. ^ E. E. Magat (1980). "Fibers from Extended Chain Aromatic Polyamides, New Fibers and Their Composites".Philosophical Transactions of the Royal Society A 294 (1411): 463–472. Bibcode:1980RSPTA.294..463M(http://adsabs.harvard.edu/abs/1980RSPTA.294..463M). doi:10.1098/rsta.1980.0055(http://dx.doi.org/10.1098%2Frsta.1980.0055). JSTOR 36370 (https://www.jstor.org/stable/36370).
34. ^ Ronald V. Joven. Manufacturing Kevlar panels by thermo-curing process. Los Andes University, 2007.Bogotá, Colombia.
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