Editing Kevlar (section)

== Production ==
[[file:Poly(p-phenylenterephthalamid)-Synthese.svg|thumb|The reaction of 1,4-phenylene-diamine (''para''-phenylenediamine) with terephthaloyl chloride yielding Kevlar]]

Kevlar is [[Chemical synthesis|synthesized]] in solution from the monomers 1,4-[[phenylene]]-di[[amine]] ([[P-Phenylenediamine|''para''-phenylenediamine]]) and [[terephthaloyl chloride]] in a [[Condensation polymer|condensation reaction]] yielding [[hydrochloric acid]] as a byproduct. The result has [[liquid crystal|liquid-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 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]], a [[patent war]] ensued.<ref>[http://www.explainthatstuff.com/kevlar.html How Kevlar® works: a simple introduction]. Explainthatstuff.com (2009-12-07). Retrieved on 2012-05-26.</ref>

Kevlar production is expensive because of the difficulties arising from using concentrated [[sulfuric acid]], needed to keep the water-insoluble polymer in solution during its synthesis and [[spinning (textiles)|spinning]].<ref>{{Cite web |url=https://www.rrc.ca/academic-news/2013/08/01/chemical-of-the-week-kevlar/ |title=Chemical of the Week: Kevlar |date=2013-08-01 |access-date=2023-09-06 |website=[[Red River College Polytechnic]]}}</ref>

Several grades of Kevlar are available:

* ''Kevlar K-29'' – in industrial applications, such as cables, [[asbestos]] 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<ref>{{Cite web|url=http://www.matweb.com/search/datasheettext.aspx?matguid=706f16a3a8be468284571dd36bbdea35|title = DuPont™ Kevlar® 149 Fiber, diam. 12 µm}}</ref><ref>{{cite web| url = https://www.researchgate.net/publication/279740540| title = Determination of Fracture Behavior under Biaxial Loading of Kevlar 149}}</ref>
* ''Kevlar AP'' – 15% higher tensile strength than K-29<ref>[http://www2.dupont.com/Kevlar/en_US/assets/downloads/K23339_KevlarAP.pdf Kevlar K-29 AP Technical Data Sheet] {{Webarchive|url=https://web.archive.org/web/20121018120411/http://www2.dupont.com/Kevlar/en_US/assets/downloads/K23339_KevlarAP.pdf |date=2012-10-18 }} – Dupont</ref>
* ''Kevlar XP'' – lighter weight resin and KM2 plus fiber combination<ref>[http://www2.dupont.com/Kevlar/en_US/products/life_protection/kevlarxp_dupont.html Kevlar XP] {{Webarchive|url=https://web.archive.org/web/20110324183411/http://www2.dupont.com/Kevlar/en_US/products/life_protection/kevlarxp_dupont.html |date=2011-03-24 }} – Dupont</ref>
* ''[[Kevlar KM2]]'' – enhanced ballistic resistance for armor applications<ref>[http://www2.dupont.com/Kevlar/en_US/products/life_protection/kevlar_km2.html Kevlar KM2 Technical Description] {{Webarchive|url=https://web.archive.org/web/20120229045242/http://www2.dupont.com/Kevlar/en_US/products/life_protection/kevlar_km2.html |date=2012-02-29 }}. dupont.com. Retrieved on 2012-05-26.</ref>

The [[Ultraviolet light|ultraviolet]] component of sunlight degrades and decomposes Kevlar, a problem known as ''[[UV degradation]]'', and so it is rarely used outdoors without protection against sunlight.<ref>{{Cite journal|last1=Yousif|first1=Emad|last2=Haddad|first2=Raghad|date=2013-08-23|title=Photodegradation and photostabilization of polymers, especially polystyrene: review|journal=SpringerPlus|volume=2|pages=398|doi=10.1186/2193-1801-2-398|issn=2193-1801|pmc=4320144|pmid=25674392 |doi-access=free }}</ref>