Editing Polyethylene (section)

==History==
Polyethylene was first synthesized by the German chemist [[Hans von Pechmann]], who prepared it by accident in 1898 while investigating [[diazomethane]].<ref name=vPechmann1898>{{cite journal |author=von Pechmann, H. |year=1898 |url=http://gallica.bnf.fr/ark:/12148/bpt6k90751n/f312.image.langEN |title=Ueber Diazomethan und Nitrosoacylamine |journal=Berichte der Deutschen Chemischen Gesellschaft zu Berlin |volume=31 |pages=2640–2646}}</ref>{{efn|{{lang|de|Erwähnt sei noch, dass aus einer ätherischen Diazomethanlösung sich beim Stehen manchmal minimale Quantitäten eines weissen, flockigen, aus Chloroform krystallisirenden Körpers abscheiden; ...}} [''It should be mentioned that from an ether solution of diazomethane, upon standing, sometimes small quantities of a white, flakey substance precipitate, which can be crystallized with chloroform; ...''].<ref name=vPechmann1898/>{{rp|2643}} }}<ref name=BambergerTschirner1900>{{cite journal |first1=Eug. |last1=Bamberger |author1-link=Eugen Bamberger |first2=Fred. |last2=Tschirner |year=1900 |url=http://gallica.bnf.fr/ark:/12148/bpt6k907551/f960.image.langEN |title=Ueber die Einwirkung von Diazomethan auf β-Arylhydroxylamine |trans-title=On the effect of diazomethane on β-arylhydroxylamine |journal=Berichte der Deutschen Chemischen Gesellschaft zu Berlin |volume=33 |pages=955–959 |doi=10.1002/cber.190003301166 }}</ref>{{efn|{{lang|de|Die Abscheidung weisser Flocken aus Diazomethanlösungen erwähnt auch v. Pechmann (diese Berichte '''31''', 2643);<ref name=vPechmann1898/> er hat sie aber wegen Substanzmangel nicht untersucht. Ich hatte übrigens Hrn.&nbsp;v.&nbsp;Pechmann schon einige Zeit vor Erscheinen seiner Publication mitgetheilt, dass aus Diazomethan ein fester, weisser Körper entstehe, der sich bei der Analyse als (CH<sub>2</sub>)<sub>x</sub> erwiesen habe, worauf mir Hr.&nbsp;v.&nbsp;Pechmann schrieb, dass er den weissen Körper ebensfalls beobachtet, aber nicht untersucht habe. Zuerst erwähnt ist derselbe in der Dissertation meines Schülers. (Hindermann, Zürich (1897), S.&nbsp;120)}}<ref name=BambergerTschirner1900/>{{rp|footnote&nbsp;3 on page&nbsp;956}} [''Von Pechmann (these ''Reports'', '''31''', 2643)<ref name=vPechmann1898/> also mentioned the precipitation of white flakes from diazomethane solutions; however, due to a scarcity of the material, he didn't investigate it. Incidentally, some time before the appearance of his publication, I had communicated to Mr.&nbsp;von&nbsp;Pechmann that a solid, white substance arose from diazomethane, which on analysis proved to be (CH<sub>2</sub>)<sub>x</sub>, whereupon Mr.&nbsp;von&nbsp;Pechmann wrote me that he had likewise observed the white substance, but not investigated it. It is first mentioned in the dissertation of my student. (Hindermann, Zürich (1897), p.&nbsp;120)''].}} When his colleagues [[Eugen Bamberger]] and Friedrich Tschirner characterized the white, waxy substance that he had created, they recognized that it contained long −CH<sub>2</sub>− chains and termed it ''polymethylene''.<ref>{{cite journal |first1=Eugen |last1=Bamberger |author1-link=Eugen Bamberger |first2=Friedrich |last2=Tschirner |year=1900 |url=http://gallica.bnf.fr/ark:/12148/bpt6k907551/f960.image.langEN |title=Ueber die Einwirkung von Diazomethan auf β-Arylhydroxylamine |trans-title=On the effect of diazomethane on β-arylhydroxylamine |journal=Berichte der Deutschen Chemischen Gesellschaft zu Berlin |volume=33 |pages=955–959 |doi=10.1002/cber.190003301166 |quote=[page 956]: {{lang|de|Eine theilweise – übrigens immer nur minimale – Umwandlung des Diazomethans in Stickstoff und Polymethylen vollzieht sich auch bei ganz andersartigen Reactionen; ...}} [''A partial – incidentally, always only minimal – conversion of diazomethane into nitrogen and polymethylene takes place also during quite different reactions; ...''] }}</ref>
[[File:First polythene pillbox.JPG|thumb|right|A [[pill box (container)|pill box]] presented to a technician at ICI in 1936 made from the first pound of polyethylene]]

The first industrially practical polyethylene synthesis (diazomethane is a notoriously unstable substance that is generally avoided in industrial syntheses) was again accidentally discovered in 1933 by Eric Fawcett and Reginald Gibson at the [[Imperial Chemical Industries]] (ICI) works in [[Northwich]], [[England]].<ref>{{cite news |url=http://archive.thisischeshire.co.uk/2006/8/23/275808.html |archive-url=https://web.archive.org/web/20100121071050/http://archive.thisischeshire.co.uk/2006/8/23/275808.html |archive-date=21 January 2010 |title=Winnington history in the making |date=23 August 2006 |work=This is Cheshire |access-date=20 February 2014 }}</ref> Upon applying extremely high pressure (several hundred [[atmosphere (unit)|atmospheres]]) to a mixture of ethylene and [[benzaldehyde]] they again produced a white, waxy material. Because the reaction had been initiated by trace [[oxygen]] contamination in their apparatus, the experiment was difficult to reproduce at first. It was not until 1935 that another ICI chemist, [[Michael Perrin]], developed this accident into a reproducible high-pressure synthesis for polyethylene that became the basis for industrial low-density polyethylene ([[Low-density polyethylene|LDPE]]) production beginning in 1939. Because polyethylene was found to have very low-loss properties at very high frequency radio waves, commercial distribution in Britain was suspended on the outbreak of World War&nbsp;II, secrecy imposed, and the new process was used to produce insulation for UHF and SHF [[coaxial cable]]s of [[radar]] sets. During World War&nbsp;II, further research was done on the ICI process and in 1944, [[DuPont]] at Sabine River, Texas, and [[Union Carbide|Union Carbide Corporation]] at South Charleston, West Virginia, began large-scale commercial production under license from ICI.<ref>{{cite news |date=July 1949 |title=Poly – the all-star plastic |work=Popular Mechanics |via=Google Books |url=https://books.google.com/books?id=GtkDAAAAMBAJ&pg=PA126 |pages=125–129 |volume=91 |issue=1 |publisher=Hearst Magazines |access-date=20 February 2014}}</ref><ref>{{cite book |title=A History of Union Carbide Corporation |page=69 |url=https://www.carbidecamps.net/UCC%20Articles/HistoryOfUCC/History%20of%20UCC%20-%20complete%20-%20single%20file.pdf}}</ref>

The landmark breakthrough in the commercial production of polyethylene began with the development of [[catalyst]]s that promoted the [[polymerization]] at mild temperatures and pressures. The first of these was a catalyst based on [[chromium trioxide]] discovered in 1951 by [[Robert Banks (chemist)|Robert Banks]] and [[J. Paul Hogan]] at [[Phillips Petroleum]].<ref>{{cite book |title=Handbook of Transition Metal Polymerization Catalysts |last1=Hoff |first1=Ray |last2=Mathers |first2=Robert T. |editor1-last=Hoff |editor1-first=Ray |editor2-last=Mathers |editor2-first=Robert T. |year=2010 |publisher=John Wiley & Sons |isbn=978-0-470-13798-7 |doi=10.1002/9780470504437.ch10 |chapter=Chapter 10. Review of Phillips Chromium Catalyst for Ethylene Polymerization}}</ref> In 1953 the German chemist [[Karl Ziegler]] developed a catalytic system based on [[titanium]] [[halide]]s and organoaluminium compounds that worked at even milder conditions than the Phillips catalyst. The Phillips catalyst is less expensive and easier to work with, however, and both methods are heavily used industrially. By the end of the 1950s both the Phillips- and [[Ziegler–Natta catalyst|Ziegler]]-type catalysts were being used for high-density polyethylene (HDPE) production. In the 1970s, the Ziegler system was improved by the incorporation of [[magnesium chloride]]. Catalytic systems based on soluble catalysts, the [[metallocene]]s, were reported in 1976 by [[Walter Kaminsky]] and [[Hansjörg Sinn]]. The Ziegler- and metallocene-based catalysts families have proven to be very flexible at copolymerizing ethylene with other [[olefin]]s and have become the basis for the wide range of polyethylene [[resin]]s available today, including [[#Very-low-density polyethylene (VLDPE)|very-low-density polyethylene]] and [[linear low-density polyethylene]]. Such resins, in the form of [[Ultra-high-molecular-weight polyethylene#UHMWfiber|UHMWPE fibers]], have (as of 2005) begun to replace [[aramid]]s in many high-strength applications.