Cellophane

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. The original production process uses carbon disulfide (CS₂), which has been found to be highly toxic to workers. The newer lyocell process 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 owned by DuPont.

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.

Cellophane was invented by Swiss chemist Jacques E. Brandenberger in 1908, while employed by Blanchisserie et Teinturerie de Thaon. Inspired by the hydrophobic effect of a restaurant tablecloth when wine was spilled on it, Brandenberger aimed to create a material which could repel liquids rather than absorb them. His initial attempt to produce such a material involved spraying a waterproof coating onto viscose cloth. The resulting coated fabric was too stiff, but after drying, the diaphanous cellulose coating could be separated easily from the backing cloth as a flexible and unbroken sheet. Recognising the possibilities of that incidental formation of a structurally-sound transparent material, Brandenberger abandoned his original method.