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Jai Ganesh

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Cellophane

Cellophane

Gist

Cellophane is a polymeric cellulose film made from the cellulose from wood, cotton, hemp, or other sources. The raw material of choice is called dissolving pulp, which is white like cotton and contains 92%–98% cellulose. The cellulose is dissolved in alkali in a process known as mercerization. It is aged several days.

Summary

Cellophane is a a thin film of regenerated cellulose, usually transparent, employed primarily as a packaging material. For many years after World War I, cellophane was the only flexible, transparent plastic film available for use in such common items as food wrap and adhesive tape. Since the 1960s it has steadily given ground to films made from synthetic polymers such as polyethylene, polyvinylidene chloride, and polyethylene terephthalate.

Cellophane emerged from a series of efforts conducted during the late 19th century to produce artificial materials by the chemical alteration of cellulose, a natural polymer obtained in large quantities from wood pulp or cotton linters. In 1892 English chemists Charles F. Cross and Edward J. Bevan patented viscose, a solution of cellulose treated with caustic soda and carbon disulfide. Viscose is best known as the basis for the man-made fibre rayon, but in 1898 Charles H. Stearn was granted a British patent for producing films from the substance. It was not until 1908, however, that Jacques E. Brandenberger, a Swiss chemist, designed a machine for continuous production of a strong, transparent film. Brandenberger coined the term cellophane by combining cellulose with diaphane, the French word for “translucent.” World War I delayed large-scale development; however, in 1913 a French company, La Cellophane SA, was formed. In 1923 E.I. du Pont de Nemours & Company (now DuPont Company) acquired rights from La Cellophane to manufacture the product in the United States. Eventually many varieties of the film were developed. While Cellophane remains a trademark in many countries in Europe and elsewhere, in the United States it is, by court decision, a generic name.

In the manufacturing process, carefully ripened viscose is piped to a casting machine, where it is extruded through a slit into an acid bath in which it coagulates into a film and is reconverted to cellulose. Driven rolls carry the film through a further series of baths, where it is washed and bleached, treated with softening materials such as glycerol, and coated with moisture-proofing materials. The treated film is passed through dryers and taken up onto large mill rolls. Cellophane is transparent, odour-resistant, tough, grease-proof, and impermeable to gases. It can be made in various thicknesses and colours, and, by the application of special coatings such as polyvinylidene chloride, it can be made moisture-proof and heat-sealing.

Details

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. Production, however, uses carbon disulfide (CS2), which has been found to be highly toxic to workers. The lyocell process, however, can be used to produce cellulose film without involving carbon disulfide.

"Cellophane" is a generic term in some countries, while in other countries it is a registered trademark.

Production

Cellulose from wood, cotton, hemp, or other sources is dissolved in alkali and carbon disulfide to make a solution called viscose, which is then extruded through a slit into a bath of dilute sulfuric acid and sodium sulfate to reconvert the viscose into cellulose. The film is then passed through several more 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, using a hole (a spinneret) instead of a slit, is used to make a fibre called rayon. Chemically, cellophane, rayon and cellulose are polymers of glucose; they differ structurally rather than chemically.

History

Cellophane was invented by Swiss chemist Jacques E. Brandenberger while employed by Blanchisserie et Teinturerie de Thaon. In 1900, inspired by seeing wine spill on a restaurant's tablecloth, he decided to create a cloth that could repel liquids rather than absorb them. His first step was to spray a waterproof coating onto fabric, and he opted to try viscose. The resultant coated fabric was far too stiff, but the diaphanous film coating could be separated from the backing cloth easily and in one undamaged piece. Seeing the possibilities of this new material on its own, Brandenberger soon abandoned his original idea.

It took ten years for Brandenberger to perfect his film. His chief improvement over earlier work with such films was adding glycerin to soften the material. By 1912 he had constructed a machine to manufacture the film, which he had named Cellophane, from the words cellulose and diaphane ("transparent"). Cellophane was patented that year. The following year, the company Comptoir des Textiles Artificiels (CTA) bought the Thaon firm's interest in Cellophane and established Brandenberger in a new company, La Cellophane SA.

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. 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.

Cellophane played a crucial role in developing the self-service retailing of fresh meat. 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 discoloration of food. 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).

The British textile company Courtaulds' viscose technology had allowed it to diversify in 1930 into viscose film, which it named "Viscacelle". However, competition with Cellophane was an obstacle to its sales, and in 1935 it founded British Cellophane Limited (BCL) in conjunction with the Cellophane Company and its French parent company CTA. A major production facility was constructed at Bridgwater, Somerset, England, from 1935 to 1937, employing 3,000 workers. BCL subsequently constructed plants in Cornwall, Ontario (BCL Canada), as an adjunct to the existing Courtaulds viscose rayon plant there (from which it bought the viscose solution), and in 1957 at Barrow-in-Furness, Cumbria. The latter two plants were closed in the 1990s.

Today

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 a certain type of battery, 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 moisture 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 contributed 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.

Material properties

When placed between two plane polarizing filters, cellophane produces prismatic colours due to its birefringent nature. Artists have used this effect to create stained glass-like creations that are kinetic and interactive.

Cellophane is biodegradable, but highly toxic carbon disulfide is used in most cellophane production. 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.

Branding

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. 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.

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