View source for Polyethylene

{{Use mdy dates|date=March 2012}}
{{Chembox
| ImageFile = Polyethylene-repeat-2D-flat.png
| ImageFile_Ref = {{chemboximage|correct|??}}
| ImageSize = 100
| ImageName = Skeletal formula of a polyethylene monomer
| ImageFile1 = Polyethylene-3D-vdW.png
| ImageFile1_Ref = {{chemboximage|correct|??}}
| ImageName1 = Spacefill model of polyethylene
| ImageFile2 = Polyethylene balls1.jpg
| ImageFile2_Ref = {{chemboximage|correct|??}}
| ImageName2 = Sample of granulated polyethylene
| IUPACName = Polyethene or Poly(methylene)
| OtherNames = Polythene
| Section1 = {{Chembox Identifiers
|  CASNo = 9002-88-4
|  CASNo_Ref = {{cascite|correct|??}}
|  KEGG = C19503
|  KEGG_Ref = {{keggcite|correct|kegg}}
|  MeSHName = Polyethylene
}}
}}
[[File:Polyethylene-repeat-2D.png|thumb|140|The repeating unit of '''polyethylene''', showing its [[stereochemistry]].]]

'''Polyethylene''' (abbreviated '''PE''') or '''polythene''' ([[IUPAC]] name '''polyethene''' or '''poly(methylene)''') is the most common [[plastic]].  The annual production is approximately 80 million metric tons.<ref>{{harvnb|Piringer|Baner|2008|p=32}}.</ref> Its primary use is in [[packaging]] ([[plastic bag]], [[plastic film]]s, [[geomembranes]], containers including [[bottle]]s, etc.). Many kinds of polyethylene are known, with most having the [[chemical formula]] (C<sub>2</sub>H<sub>4</sub>)<sub>n</sub>H<sub>2</sub>.  Thus PE is usually a mixture of similar [[organic compound]]s that differ in terms of the value of n.

==Properties==

===Physical properties===
Polyethylene is a [[thermoplastic]] [[polymer]] consisting of long hydrocarbon chains.  Depending on the [[crystal structure|crystallinity]] and [[molecular weight]], a [[melting point]] and [[glass transition]] may or may not be observable. The temperature at which these occur varies strongly with the type of polyethylene. For common commercial grades of medium- and high-density polyethylene the melting point is typically in the range {{convert|120|to|130|C|F}}. The melting point for average, commercial, low-density polyethylene is typically {{convert|105|to|115|C|F}}.

===Chemical properties===
Most LDPE, MDPE and HDPE grades have excellent chemical resistance, meaning that it is not attacked by strong acids or strong bases.  It is also resistant to gentle oxidants and reducing agents. Polyethylene burns slowly with a blue flame having a yellow tip and gives off an odour of paraffin. The material continues burning on removal of the flame source and produces a drip.<ref>{{cite web |url=http://www.boedeker.com/burntest.htm |title=How to Identify Plastic Materials Using The Burn Test |work=Boedeker Plastics |accessdate=8 May 2012}}</ref> Crystalline samples do not dissolve at room temperature. Polyethylene (other than cross-linked polyethylene) usually can be dissolved at elevated temperatures in [[aromatic hydrocarbon]]s such as [[toluene]] or [[xylene]], or in chlorinated solvents such as [[trichloroethane]] or [[trichlorobenzene]].<ref name=Ullmann>Kenneth S. Whiteley, T. Geoffrey Heggs, Hartmut Koch, Ralph L. Mawer, Wolfgang Immel, "Polyolefins" in Ullmann's Encyclopedia of Industrial Chemistry 2005, Wiley-VCH, Weinheim. {{DOI|10.1002/14356007.a21_487}}</ref>

==Process==

===Monomer===
{{multiple image
| direction = vertical
| align = right
| image1 = Ethylene.svg
| width1 = 140
| alt1 = ethylene skeleton
| image2 = Ethylene-3D-vdW.png
| width2 = 140
| alt2 = ethylene 3D model
| footer = Ethylene (ethene).
}}
The ingredient or [[monomer]] is [[ethylene]] ([[IUPAC]] name ethene), a [[gas|gaseous]] [[hydrocarbon]] with the formula C<sub>2</sub>H<sub>4</sub>, which can be viewed as a pair of [[methylene group]]s (={{chem|CH|2}}) connected to each other. Because the catalysts are highly reactive, the ethylene must be of high purity. Typical specifications are <5 ppm for water, oxygen, as well as other alkenes.  Acceptable contaminants include N<sub>2</sub>, ethane (common precursor to ethylene), and methane.  Ethylene is usually produced from petrochemical sources, but also is generated by dehydration of ethanol.<ref name="Ullmann"/>

===Polymerization===
Ethylene is a rather stable molecule that polymerizes only upon contact with catalysts.  The conversion is highly exothermic, that is the process releases a lot of heat. [[Coordination polymerization]] is the most pervasive technology, which means that metal chlorides or metal oxides are used.  The most common catalysts consist of [[titanium(III) chloride]], the so-called [[Ziegler-Natta catalyst]]s.  Another common catalyst is the Phillips catalyst, prepared by depositing [[chromium trioxide|chromium(VI) oxide]] on silica.<ref name="Ullmann"/>  Ethylene can be produced through [[radical polymerization]], but this route has only limited utility and typically requires high pressure apparatus.

==Classification==
Polyethylene is classified into several different categories based mostly on its [[density]] and [[Branching (chemistry)|branching]]. Its mechanical properties depend significantly on variables such as the extent and type of branching, the crystal structure and the [[molecular weight]]. With regard to sold volumes, the most important polyethylene grades are HDPE, LLDPE and LDPE.

*[[Ultra-high-molecular-weight polyethylene]] (UHMWPE)
*[[Ultra-low-molecular-weight polyethylene]] (ULMWPE or PE-WAX)
*[[High-molecular-weight polyethylene]] (HMWPE)
*[[High-density polyethylene]] (HDPE)
*[[High-density cross-linked polyethylene]] (HDXLPE)
*[[Cross-linked polyethylene]] (PEX or XLPE)
*[[Medium-density polyethylene]] (MDPE)
*[[Linear low-density polyethylene]] (LLDPE)
*[[Low-density polyethylene]] (LDPE)
*[[Very-low-density polyethylene]] (VLDPE)
*[[Chlorinated polyethylene]] (CPE)

===Ultra-high-molecular-weight polyethylene (UHMWPE)===
[[File:Stainless steel and ultra high molecular weight polythene hip replacement (9672239334).jpg|thumb|Stainless steel and ultra high molecular weight polythene hip replacement]]
UHMWPE is polyethylene with a molecular weight numbering in the millions, usually between 3.1 and 5.67 million. The high molecular weight makes it a very [[toughness|tough]] material, but results in less efficient packing of the chains into the [[crystal structure]] as evidenced by densities of less than high density polyethylene (for example, 0.930–0.935 g/cm<sup>3</sup>). UHMWPE can be made through any catalyst technology, although Ziegler catalysts are most common. Because of its outstanding toughness and its cut, wear and excellent chemical resistance, UHMWPE is used in a diverse range of applications. These include can and [[bottle]] handling machine parts, moving parts on weaving machines, bearings, gears, artificial joints, edge protection on ice rinks and butchers' chopping boards. It competes with [[aramid]] in [[bulletproof vests]], under the tradenames Spectra and Dyneema, and is commonly used for the construction of articular portions of [[implant (medicine)|implants]] used for [[hip replacement|hip]] and [[knee replacement]]s.

===High-density polyethylene (HDPE)===

[[File:Hdpe pipe installation.jpg|thumb|[[High-density polyethylene|HDPE]] pipe installation in storm drain project in [[Mexico]].]]
HDPE is defined by a density of greater or equal to 0.941 g/cm<sup>3</sup>. HDPE has a low degree of branching and thus low intermolecular forces and tensile strength. HDPE can be produced by [[chromium]]/silica catalysts, [[Ziegler-Natta catalyst]]s or [[metallocene]] catalysts. The lack of branching is ensured by an appropriate choice of catalyst (for example, chromium catalysts or Ziegler-Natta catalysts) and reaction conditions. HDPE is used in products and packaging such as milk jugs, detergent bottles, butter tubs, garbage containers and water pipes. One third of all toys are manufactured from HDPE. In 2007 the global HDPE consumption reached a volume of more than 30 million tons.<ref>{{cite web |url=http://www.ceresana.com/en/market-studies/plastics/polyethylene-hdpe/ |title=Market Study: Polyethylene – HDPE |year=2012 |month=May |publisher=Ceresana Research |accessdate=8 May 2012}}</ref>

===Cross-linked polyethylene (PEX or XLPE)===
{{Main|PEX}}

PEX is a medium- to high-density polyethylene containing [[cross-link]] bonds introduced into the polymer structure, changing the thermoplast into an [[thermoset]]. The high-temperature properties of the polymer are improved, its flow is reduced and its chemical resistance is enhanced. PEX is used in some potable-water plumbing systems because tubes made of the material can be expanded to fit over a metal nipple and it will slowly return to its original shape, forming a permanent, water-tight, connection.

===Medium-density polyethylene (MDPE)===

MDPE is defined by a density range of 0.926–0.940 g/cm<sup>3</sup>. MDPE can be produced by chromium/silica catalysts, Ziegler-Natta catalysts or metallocene catalysts. MDPE has good shock and drop resistance properties. It also is less notch-sensitive than HDPE, stress cracking resistance is better than HDPE. MDPE is typically used in gas pipes and fittings, sacks, shrink film, packaging film, carrier bags and screw closures.

===Linear low-density polyethylene (LLDPE)===

LLDPE is defined by a density range of 0.915–0.925 g/cm<sup>3</sup>. LLDPE is a substantially linear polymer with significant numbers of short branches, commonly made by [[copolymerization]] of ethylene with short-chain [[alpha-olefin]]s (for example, [[1-butene]], [[1-Hexene|1-hexene]] and [[1-octene]]). LLDPE has higher tensile strength than LDPE, it exhibits higher impact and [[puncture resistance]] than LDPE. Lower thickness (gauge) films can be blown, compared with LDPE, with better environmental stress cracking resistance but is not as easy to process. LLDPE is used in packaging, particularly film for bags and sheets. Lower thickness may be used compared to LDPE. Cable covering, toys, lids, buckets, containers and pipe. While other applications are available, LLDPE is used predominantly in film applications due to its toughness, flexibility and relative transparency. Product examples range from agricultural films, saran wrap, and bubble wrap, to multilayer and composite films. In 2009 the world LLDPE market reached a volume of almost US$24 billion (€17 billion).<ref>{{cite web |url=http://www.ceresana.com/en/market-studies/plastics/polyethylene-lldpe/ |title=Market Study: Polyethylene – LLDPE |year=2010 |month=March |publisher=Ceresana Research |accessdate=8 May 2012}}</ref>

===Low-density polyethylene (LDPE)===

LDPE is defined by a density range of 0.910–0.940 g/cm<sup>3</sup>. LDPE has a high degree of short and long chain branching, which means that the chains do not pack into the [[crystal structure]] as well. It has, therefore, less strong intermolecular forces as the [[instantaneous-dipole induced-dipole attraction]] is less. This results in a lower [[tensile strength]] and increased [[ductility]]. LDPE is created by [[Radical polymerization|free radical polymerization]]. The high degree of branching with long chains gives molten LDPE unique and desirable flow properties. LDPE is used for both rigid containers and plastic film applications such as plastic bags and film wrap. In 2009 the global LDPE market had a volume of circa US$22.2 billion (€15.9 billion).<ref>{{cite web |url=http://www.ceresana.com/en/market-studies/plastics/polyethylene-ldpe/ |title=Market Study: Polyethylene – LDPE |year=2010 |month=April |publisher=Ceresana Research |accessdate=8 May 2012}}</ref>

===Very-low-density polyethylene (VLDPE)===

VLDPE is defined by a density range of 0.880–0.915 g/cm<sup>3</sup>. VLDPE is a substantially linear polymer with high levels of short-chain branches, commonly made by copolymerization of ethylene with short-chain alpha-olefins (for example, 1-butene, 1-hexene and 1-octene). VLDPE is most commonly produced using metallocene catalysts due to the greater co-monomer incorporation exhibited by these catalysts. VLDPEs are used for hose and tubing, ice and frozen food bags, food packaging and stretch wrap as well as impact modifiers when blended with other polymers.

Recently much research activity has focused on the nature and distribution of long chain branches in polyethylene. In HDPE a relatively small number of these branches, perhaps 1 in 100 or 1,000 branches per backbone carbon, can significantly affect the [[rheology|rheological]] properties of the polymer.

===Copolymers===
In addition to [[copolymerization]] with alpha-olefins, ethylene can also be copolymerized with a wide range of other monomers and ionic composition that creates ionized free radicals. Common examples include [[vinyl acetate]] (the resulting product is [[ethylene-vinyl acetate]] copolymer, or EVA, widely used in athletic-shoe sole foams) and a variety of [[acrylate]]s. Applications of [[Acrylic resin|acrylic]] [[copolymer]] include packaging and sporting goods, and [[superplasticizer]], used for cement production.

==History==
Polyethylene was first synthesized by the German chemist [[Hans von Pechmann]] who prepared it by accident in 1898 while heating [[diazomethane]]. 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''.
[[File:First polythene pillbox.JPG|thumb|right|A [[Pillbox|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 application) was discovered in 1933 by Eric Fawcett and Reginald Gibson, again by accident, at the [[Imperial Chemical Industries|ICI]] works in [[Northwich]], England.<ref>{{cite web |url=http://archive.thisischeshire.co.uk/2006/8/23/275808.html |archiveurl=http://web.archive.org/web/20100121071050/http://archive.thisischeshire.co.uk/2006/8/23/275808.html |archivedate=2010-01-21 |title=Winnington history in the making |date=23 August 2006 |work=This is Cheshire |accessdate=5 December 2006 |ref=harv}}</ref> Upon applying extremely high pressure (several hundred 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, at first, difficult to reproduce. 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 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 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 II, further research was done on the ICI process and in 1944 Bakelite Corporation at Sabine, Texas and Du Pont at Charleston, West Virginia, began large scale commercial production under license from ICI.<ref>{{cite journal |year=1949 |month=July |title=Poly – The All Star Plastic |magazine=Popular Mechanics |page=126 |publisher=Popular Mechanics Company |url=http://books.google.com/books?id=GtkDAAAAMBAJ&pg=PA126|accessdate=8 May 2012}}</ref>

The breakthrough landmark in the commercial production of polyethylene began with the development of [[catalyst]] that promote the polymerization at mild temperatures and pressures. The first of these was a [[chromium trioxide]]–based catalyst 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 |month=March |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}}<!--Ray Hoff, Robert T. Mathers Chapter 10. Review of Phillips Chromium Catalyst for Ethylene Polymerization" in "Handbook of Transition Metal Polymerization Catalysts" Ray Hoff, Robert T. Mathers, Eds. 2010 John Wiley & Sons, Inc. {{DOI|10.1002/9780470504437.ch10}}--></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 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]] and [[linear low-density polyethylene]]. Such resins, in the form of fibers like [[Dyneema]], have (as of 2005) begun to replace [[aramid]]s in many high-strength applications.

==Environmental issues==
[[File:Polyethylene.jpg|thumb|140|A bag manufactured from polyethylene.]]
{{cleanup|section|reason=unsourced, poorly sourced, and innacurate statements|date=September 2012}}
Although ethylene can be produced from renewables, polyethylene is mainly made from petroleum or natural gas.

===Biodegrading plastics===
One of the main problems of polyethelyne is that without special treatment it is not readily biodegradable, and thus accumulates. In Japan getting rid of plastics in an environmentally friendly way was the major problem discussed until the [[Fukushima Daiichi nuclear disaster|Fukushima disaster]] in 2011. It was listed as a $90 billion market for solutions. Since 2008 Japan has rapidly increased the recycling of plastics, but still has a large rate of plastic wrapping which goes to waste.<ref name="prideaux2007">{{cite news |title=Plastic incineration rise draws ire |first=Eric |last=Prideaux |url=http://www.japantimes.co.jp/text/nn20071103f2.html |newspaper=The Japan Times Online |date=3 November 2007 |accessdate=8 May 2012}}</ref><ref name="prideaux2007"/><!--[http://www.japantimes.co.jp/text/nn20071103f2.html Incinerating plastic in Japan] a 2007 article in Japan times. [http://www.guardian.co.uk/environment/2011/dec/29/japan-leads-field-plastic-recycling Japan plastics recycling] (The Guardian 2010)-->

In May 2008, Daniel Burd, a 16-year-old Canadian, won the [[Canada-Wide Science Fair]] in Ottawa after discovering that ''[[Pseudomonas fluorescens]]'', with the help of ''[[Sphingomonas]]'', can degrade over 40% of the weight of plastic bags in less than three months.<ref>{{cite web |url=http://woohooreport.com/2009/09/wci-student-isolates-microbe-that-lunches-on-plastic-bags/|publisher=The Record.com |title=CanadaWorld – WCI student isolates microbe that lunches on plastic bags}}</ref>

In 2009 it was discovered by a resident of Hawaii upon returning from a ship race that degraded plastics are a major cause for marine life destruction, being mixed in with plankton, comparable in size and weight but in much larger numbers.<ref>[http://www.telegraph.co.uk/earth/environment/5208645/Drowning-in-plastic-The-Great-Pacific-Garbage-Patch-is-twice-the-size-of-France.html Drowning in Plastic] A Daily Telegraph article from 2009 about the discovery of the plastic particles from degrading plastics and Polyethylene.</ref>

In 2010 a Japanese researcher Akinori Ito released the prototype of a machine which creates oil from Polyethylene using a small, self-contained vapor distillation process.<ref>[http://www.smartplanet.com/blog/thinking-tech/new-invention-turns-plastic-bags-into-oil/6295 Plastic into biodiesel machine] (at smartplanet.com website)</ref>

===Bio-derived polyethylene===
{{Main|Bioplastics|Renewable Polyethylene}}

[[Braskem]] and [[Toyota Tsusho Corporation]] started Joint marketing activities for producing polyethylene from [[sugar cane]]. Braskem will build a new facility at their existing industrial unit in Triunfo, RS, Brazil with an annual production capacity of {{convert|200000|ST|kg}}, and will produce high-density polyethylene (HDPE) and low-density polyethylene (LDPE) from [[bioethanol]] derived from [[sugarcane]].<ref>[http://www.yourindustrynews.com/blog/?p=2390 Braskem & Toyota Tsusho start joint marketing activities for green polyethylene from sugar cane]. yourindustrynews.com (2008-09-26)</ref>

Polyethylene can also be made from other feedstocks, including [[wheat grain]] and [[sugar beet]]. Retrieved from cane sugar, i.e. plant biomass renewable feedstock; Brazil is the first country to develop the product<ref>[http://www.nnfcc.co.uk/metadot/index.pl?id=10220;isa=Category;op=show Life Cycle Assessment Workbooks for a Selection of Major Renewable Chemicals]. Nnfcc.co.uk. Retrieved on 2012-06-09.</ref>

These developments are using renewable resources rather than fossil fuel, although the issue of plastic source is currently negligible in the wake of plastic waste and in particular polyethylene waste as shown above.

==Joining==
Commonly used methods for joining polyethylene parts together include:<ref name="pdl">{{harvnb|Plastics Design Library||p=326}}.</ref>

*[[Hot gas welding]]
*[[Fasteners|Fastening]]
*[[Infrared welding]]
*[[Laser welding]]
*[[Ultrasonic welding]]
*[[Heat seal]]ing
*[[Heat fusion]]

[[Adhesive]]s and [[solvent]]s are rarely used because polyethylene is [[nonpolar]] and has a high resistance to solvents. [[Pressure-sensitive adhesive]]s (PSA) are feasible if the surface is [[flame treatment|flame treated]] or [[corona treatment|corona treated]].
Commonly used adhesives include:<ref name="pdl"/>

*Dispersion of solvent-type PSAs
*Polyurethane contact adhesives
*Two-part [[polyurethane adhesive|polyurethane]] or [[epoxy adhesive]]s
*[[Vinyl acetate]] [[copolymer]] [[hot melt adhesive]]s

===Nomenclature and general description of the process===
The name polyethylene comes from the ingredient and not the resulting chemical compound, which contains no double bonds. The scientific name ''polyethene'' is systematically derived from the scientific name of the monomer.<ref name=guide/><ref name="Kahovec">{{cite journal|doi=10.1351/pac200274101921|title=Nomenclature of regular single-strand organic polymers (IUPAC Recommendations 2002)|year=2002|last1=Kahovec|first1=J.|last2=Fox|first2=R.B.|last3=Hatada|first3=K.|journal=Pure and Applied Chemistry|volume=74|page=1921|ref=harv|issue=10}}</ref> The alkene monomer converts to a long, sometimes ''very'' long, alkane in the polymerization process.<ref name="Kahovec" /> In certain circumstances it is useful to use a structure-based nomenclature; in such cases [[IUPAC]] recommends poly(methylene) (poly(methanediyl) is a non-preferred alternative).<ref name=guide>[http://www.acdlabs.com/iupac/nomenclature/93/r93_683.htm A Guide to IUPAC Nomenclature of Organic Compounds (Recommendations 1993)] IUPAC, Commission on Nomenclature of Organic Chemistry, 1993, Blackwell Scientific Publications ISBN 0632037024. The difference in names between the two systems is due to the ''opening up'' of the monomer's double bond upon polymerization.</ref><ref>[http://old.iupac.org/reports/provisional/abstract04/favre_310305.html IUPAC Provisional Recommendations on the ''Nomenclature of Organic Chemistry''] by H. A. Favre and W. H. Powell, ''circa'' 2005.</ref> The name is abbreviated to '''PE'''.  In a similar manner [[polypropylene]] and [[polystyrene]] are shortened to PP and PS, respectively. In the United Kingdom the polymer is commonly called '''polythene''', although this is not recognized scientifically.

==References==
{{Reflist|35em}}

==Bibliography==
*{{Cite book|last = Piringer|first = Otto G.|last2 = Baner|first2 = Albert Lawrence|title = Plastic packaging: interactions with food and pharmaceuticals|publisher = Wiley-VCH|year = 2008|edition = 2nd|url = http://books.google.com/?id=UbOFgsNEHbAC|isbn = 978-3-527-31455-3|ref = harv}}
*{{Cite book|last = Plastics Design Library|title = Handbook of Plastics Joining: A Practical Guide|publisher = William Andrew|year = 1997|edition = Illustrated|url = http://books.google.com/?id=B-F5pXuj_M8C|isbn = 978-1-884207-17-4|ref = harv}}

==External links==
{{Wiktionary}}
{{Commons category|Polyethylene}}
*[http://www.independent.co.uk/news/science/polythenes-story-the-accidental-birth-of-plastic-bags-800602.html Polythene's story: The accidental birth of plastic bags]
*[http://www.ides.com/generics/PE.htm Polythene Technical Properties & Applications]
*[http://pqasb.pqarchiver.com/therecord/access/1482573421.html?FMT=ABS&FMTS=ABS:FT&date=May+22%2C+2008&author=Karen+Kawawada&pub=Waterloo+Region+Record&edition=&startpage=A.1&desc=WCI+student+isolates+microbe+that+lunches+on+plastic+bags Article describing the discovery of ''Sphingomonas'' as a biodegrader of plastic bags] Kawawada, Karen, The Record (May 22, 2008).
{{Plastics}}
{{Fibers}}

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