Cellophane
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Cellophane is a thin, transparent sheet made of regenerated cellulose. Its low permeability to air, oils, greases, bacteria, and liquid water makes it useful for food packaging. Cellophane is highly permeable to water vapour, but may be coated with nitrocellulose lacquer to prevent this.
Cellophane is also used in transparent pressure-sensitive tape, tubing, and many other similar applications.
Cellophane is compostable and biodegradable, and can be obtained from biomaterials.<ref name="auto">Template:Cite book</ref> The original production process uses carbon disulfide (CS2), which has been found to be highly toxic to workers.<ref name=Blanc>Template:Cite news</ref> The newer lyocell process can be used to produce cellulose film without involving carbon disulfide.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
"Cellophane" is a generic term in some countries,<ref name="gc">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> while in other countries it is a registered trademark owned by DuPont.<ref name="gc"/>
ProductionEdit
Cellulose is produced from wood, cotton, hemp, and other organic fibres, dissolved in alkali and carbon disulfide to make a solution of liquid viscose. The solution is then extruded through a slit into a bath of dilute sulfuric acid and sodium sulfate to reconvert the viscose into a cellulose film. The film is then passed through a further series of baths; one to remove sulfur, one to bleach the film, and one to add softening materials, such as glycerin, to prevent the film from becoming brittle.
A similar process is used to make rayon fibre, wherein the viscose solution is extruded through a spinneret, to form cellulose filaments, rather than a slit, which forms cellulose film.
Cellophane - like (filamentous) viscose, rayon and cellulose - is a polymer of glucose; insofar as cellophane is structurally different to monomeric glucose, while its chemical composition is the same.
HistoryEdit
Cellophane was invented by Swiss chemist Jacques E. Brandenberger in 1910, while employed by Blanchisserie et Teinturerie de Thaon.<ref>Template:Cite book</ref> Inspired by the Hydrophobic effect of a restaurant tablecloth and a wine spill, Brandenburger aimed to create a material which could repel liquids, rather than absorb them. Brandenberger's initial attempt to produce such a material involved spraying a waterproof coating onto viscose cloth. The resulting coated fabric was too stiff, however—upon drying—the diaphanous cellulose coating could be easily separated from the backing cloth in one, flexible and unbroken sheet. Recognising the possibilities of this incidental formation of a structurally-sound material, Brandenberger abandoned his original method.
It took ten years for Brandenberger to perfect his film. His chief improvement of his original cellophane-like film was to add glycerin to soften the material. By 1912 he had constructed a machine to manufacture the film, named "Cellophane"—a portmanteau of cellulose and diaphane ("transparent"). The product film, Cellophane, was patented that year.<ref>Carlisle, Rodney (2004). Scientific American Inventions and Discoveries, p.338. John Wiley & Sons, Inc., New Jersey. Template:ISBN.</ref> The following year, Comptoir des Textiles Artificiels (CTA) bought Thaon firm's interest in Cellophane and Brandenberger in a new company, La Cellophane SA.<ref name="hounshell170">Template:Cite book</ref>
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Whitman's candy company initiated use of cellophane for candy wrapping in the United States in 1912 for their Whitman's Sampler. They remained the largest user of imported cellophane from France until nearly 1924, when DuPont built the first cellophane manufacturing plant in the US. Cellophane saw limited sales in the US at first since while it was waterproof, it was not moisture proof—it held or repelled water but was permeable to water vapor. This meant that it was unsuited to packaging products that required moisture proofing. DuPont hired chemist William Hale Charch (1898–1958), who spent three years developing a nitrocellulose lacquer that, when applied to Cellophane, made it moisture proof.<ref>Template:Cite book</ref> Following the introduction of moisture-proof Cellophane in 1927, the material's sales tripled between 1928 and 1930, and in 1938, Cellophane accounted for 10% of DuPont's sales and 25% of its profits.<ref name="hounshell170" />
Cellophane played a crucial role in developing the self-service retailing of fresh meat.<ref name="hisano" /> Cellophane visibility helped customers know quality of meat before buying. Cellophane also worked to consumers' disadvantage when manufacturers learned to manipulate the appearance of a product by controlling oxygen and moisture levels to prevent discolouration of food.<ref name="hisano">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It was considered such a useful invention that cellophane was listed alongside other modern marvels in the 1934 song "You're the Top" (from Anything Goes).<ref>Template:Cite book</ref><ref>Template:Cite book</ref><ref>Template:Cite book</ref>
A British textile company—Courtaulds' viscose technology—diversified their operations in 1930 to include into viscose film named "Viscacelle". However, competition with the commercially-successful Cellophane hindered sales of Viscacelle, and in 1935, resulted in the founding of British Cellophane Limited (BCL)—in conjunction with the Cellophane Company and its French parent company CTA.<ref>Template:Cite book</ref> BCL subsequently established a major production facility at Bridgwater, Somerset, England, between 1935 and 1937, which employed 3,000 workers. Further cellophane production plants were opened at Cornwall, Ontario (BCL Canada) - adjunct to the pre-existing Courtaulds viscose rayon plant, and from which it bought the viscose solution - and at Barrow-in-Furness, Cumbria. The latter two plants were closed in the 1990s.
TodayEdit
Cellulose film has been manufactured continuously since the mid-1930s and is still used today. As well as packaging a variety of food items, there are also industrial applications, such as a base for such self-adhesive tapes as Sellotape and Scotch Tape, a semi-permeable membrane in some alkaline manganese dioxide batteries,<ref>David Linden; Thomas B. Reddy (1995) Handbook of Batteries 3d ed. p. 250 ISBN 0-07-135978-8</ref> as dialysis tubing (Visking tubing), and as a release agent in the manufacture of fibreglass and rubber products. Cellophane is the most popular material for manufacturing cigar packaging; its permeability to water vapor makes cellophane a good product for this application as cigars must be allowed to "breathe" while wrapped and in storage.
Cellophane sales have dwindled since the 1960s, due to alternative packaging options. The polluting effects of carbon disulfide and other by-products of the process used to make viscose may have also contributedTemplate:Citation needed to its falling behind lower cost petrochemical-based films such as biaxially-oriented polyethylene terephthalate (BoPET) and biaxially oriented polypropylene (BOPP) in the 1980s and 1990s. However, as of 2017, it has made something of a resurgence in recent times due to its being biosourced, compostable, and biodegradable. Its sustainability record is clouded by its energy-intensive manufacturing process and the potential negative impact of some of the chemicals used, but significant progress in recent years has been made by leading manufacturers in reducing their environmental footprint.<ref name="auto"/>
Material propertiesEdit
When placed between two plane polarizing filters, cellophane produces prismatic colours, due to its birefringent properties. This effect is often used to create stained glass-like effects in kinetic and interactive artworks.
While cellophane is biodegradable, carbon disulfide—used in most cellophane production—is highly toxic. Viscose factories vary widely in the amount of CS2 they expose their workers to, and most give no information about their quantitative safety limits or how well they keep to them.<ref name=Blanc/><ref name="scientificamerican.com">Template:Cite journal</ref>
BrandingEdit
In the UK and in many other countries, "Cellophane" is a registered trademark and the property of Futamura Chemical UK Ltd, based in Wigton, Cumbria, United Kingdom.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In the USA and some other countries "cellophane" has become genericized, and is often used informally to refer to a wide variety of plastic film products—even those not made of cellulose—such as PVC-based plastic wrap.