View source for Polyvinylidene chloride

{{distinguish|text=[[polyvinyl chloride]] (PVC)}}

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| ImageFile = Polyvinylidenchlorid.svg
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| ImageName = Skeletal formula of polyvinylidenechloride =
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| IUPACName = Poly(1,1-dichloroethene)<ref name="pubchem">{{cite web |title=Vinylidene Chloride |url=https://pubchem.ncbi.nlm.nih.gov/compound/6366 |website=pubchem.ncbi.nlm.nih.gov |access-date=28 August 2019}}</ref>
| OtherNames = Poly(vinylidene dichloride)<Br/>Polydene
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| Abbreviations = PVDC
| CASNo = 9002-85-1
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| Section2 = {{Chembox Properties
| Formula = (C<sub>2</sub>H<sub>2</sub>Cl<sub>2</sub>)<sub>n</sub>
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'''Polyvinylidene chloride''', or '''polyvinylidene dichloride''' ('''PVDC'''), is a [[homopolymer]] of [[vinylidene chloride]].

== History ==
Ralph Wiley accidentally discovered polyvinylidene chloride polymer in 1933.<ref name="Klooster2009">{{cite book|author=John W. Klooster|title=Icons of Invention: The Makers of the Modern World from Gutenberg to Gates|url=https://books.google.com/books?id=WKuG-VIwID8C&pg=PA466|access-date=12 July 2012|date=30 July 2009|publisher=ABC-CLIO|isbn=978-0-313-34743-6|pages=466–}}</ref> At the time he was a college student who worked part-time at [[Dow Chemical]] lab as a dishwasher.<ref name="ColeBrowning2003">{{cite book|author1=David John Cole|author2=Eve Browning|author3=Fred E. H. Schroeder|title=Encyclopedia of Modern Everyday Inventions|url=https://books.google.com/books?id=rVQfBSlAZvAC&pg=PA129|access-date=12 July 2012|date=30 April 2003|publisher=Greenwood Publishing Group|isbn=978-0-313-31345-5|page=129}}</ref> While cleaning laboratory glassware, he came across a vial he could not scrub clean. Dow researchers made this material into a greasy, dark green film,<ref name="Smith2007">{{cite book|author=Andrew F. Smith|title=The Oxford Companion to American Food and Drink|url=https://books.google.com/books?id=AoWlCmNDA3QC&pg=PT492|access-date=12 July 2012|date=1 May 2007|publisher=Oxford University Press|isbn=978-0-19-530796-2|page=492}}</ref> first called "Eonite" and then "[[Saran (plastic)|Saran]]".<ref name="ColeBrowning2003" /><ref>{{cite web | url=http://inventors.about.com/library/inventors/blsaranwrap.htm | archive-url=https://archive.today/20120524203558/http://inventors.about.com/library/inventors/blsaranwrap.htm | url-status=dead | archive-date=May 24, 2012 | title=Saran Wrap ® | work=inventors.about.com | access-date=July 12, 2012 | author=Mary Bellis}}</ref>

Ralph Wiley went on to become one of Dow Chemical's research scientists and invent and develop many plastics, chemicals and production machines.
 
The military sprayed Saran on fighter planes to guard against salty sea spray, and carmakers used it for upholstery. Dow later devised a formulation of polyvinylidene chloride free of unpleasant odour and green colour.

The most well known use of polyvinylidene chloride came in 1953, when [[Saran Wrap]], a plastic food wrap, was introduced. In 2004, however, the formula was changed to [[low-density polyethylene]] due to environmental concerns about its chlorine content and other [[Polyvinylidene_chloride#Disadvantages|disadvantages]].

== Properties ==
It is a remarkable barrier against water, oxygen, and aromas. It has a superior chemical resistance to [[alkali]]s and [[acid]]s, is insoluble in oil and organic solvents, has a very low moisture regain and is impervious to mold, bacteria, and insects. It is soluble in [[polar solvent]]s.

Above 125 °C, it decomposes to produce [[HCl]].<ref name="PiringerBaner2008">{{cite book|author1=Otto G. Piringer|author2=A. L. Baner|title=Plastic Packaging: Interactions with Food and Pharmaceuticals|url=https://books.google.com/books?id=wxvTeGVK5o8C&pg=PA41|access-date=12 July 2012|date=17 September 2008|publisher=John Wiley & Sons|isbn=978-3-527-62143-9|pages=41–}}</ref>

=== Disadvantages ===
While extremely useful as a [[food packaging]] agent, the major disadvantage of polyvinylidene chloride is that it will undergo thermally induced dehydrochlorination at temperatures very near to processing temperatures. This degradation easily propagates, leaving [[polyene]] sequences long enough to absorb visible light and change the color of the material from colorless to an undesirable transparent brown (unacceptable for one of polyvinylidene chloride's chief applications: food packaging). Therefore, there is a significant amount of product loss in the manufacturing process, which increases production and consumer costs.{{Citation needed|date=November 2024}}

== Fiber types ==
Saran fiber is produced in monofilament, multifilament-twist, and [[Staple (textiles)|staple fiber]] forms. It is also available in [[thermochromic]] (color changing) and [[luminescent]] (glow in the dark) fibers.

== Uses ==

=== Packaging ===
Polyvinylidene chloride is applied as a water-based coating to films made of other plastics, such as biaxially-oriented [[polypropylene]] (BOPP) and [[polyester|polyethylene terephthalate]] (PET). This coating increases the barrier properties of the film, reducing the permeability of the film to [[oxygen]] and flavours and thus extending the [[shelf life]] of the food inside the package. It can also impart a high-gloss finish, which may be aesthetically pleasing and also provides a high degree of scuff resistance if applied over print.

=== Other ===

In household settings, PVDC is used in cleaning cloths, filters, screens, tape, shower curtains, and garden furniture. Industrially, it is used in screens, artificial turf, waste-water treatment materials, and underground materials. PVDC is also used in doll hair, stuffed animals, fabrics, fishnet, pyrotechnics, and shoe insoles. It was used in [[Vesicular film|special photographic film.]]

== Trademarks (producers) ==
{{main|Saran (plastic)}}
*Saran TC and Saran LS (Asahi-Kasei)
* (formerly) Saran Wrap and Saranex (Dow Chemical)
*Ixan and Diofan (SolVin)
*SK Saran

== References ==
{{Reflist}}
* B.A. Howell, J. Polym. Sci., Polym. Chem. (ed) 1987, 25, 1681–1695.
* B.A. Howell, B.S. Warner, C.V. Rajaram, S.I. Ahemed and Z. Ahmed, Polym. Adv. Technol., 1994, 5, 485.
* B.A. Howell and S. M. Jane, “Impact of Moisture on the Thermal Stability of Vinylidene Chloride Copolymers”,  Proceedings, 34th Annual Meeting of the North American Thermal Analysis Society, 2006.
* R.A. Wessling, D.S. Gibbs P.T. Delassus, B.E. Obi, B.A. Howell, Kirk-Othmer Encyclopedia of Chemical Technology, John Wiley and Sons, New York, 4th Edition, 1997, Vol 24, pp.&nbsp;883–923.

== External links ==
* [https://web.archive.org/web/20060813202644/http://www.plastiquarian.com/wiley.htm Wiley mini-bio]
* [https://web.archive.org/web/20070716230628/http://www.tex.in/fiber/fiber.html Textile Fibre Database]

{{Plastics}}

[[Category:Thermoplastics]]