Cellophane

Cellophane is a transparent, tough, flexible film prepared from wood pulp and used extensively in food packaging. It is essentially a form of .pure cellulose. Cellophane was developed in 1908 by the French chemist Jacques Edwin Brandenberger, who derived the name from the words cellulose and diaphanes, a Greek word meaning "transparent".

In the production of cellophane, the wood pulp is first treated with sodium hydroxide and then shredded, aged, and reacted with carbon di-sulfide. This series of reactions results in the formation of a cellulose derivative, sodium cellulose xanthate, which is then dispersed in dilute sodium hydroxide to form a thick, syrupy solution called viscose. After aging, the viscose is extruded through a long thin slot into a bath of sulfuric acid and sodium sulfate. The bath coagulates the viscose into a film; carbon disulfide and hydrogen sulfide are evolved, and the cellulose is regenerated. The film is led through a series of tanks where it is washed, chemically purified, and combined with a softener or plasticizer. The wet, softened film is then dried to a controlled moisture content.

Finally, the cellophane is moisture-proofed by the application of specially designed coating lacquers, some of which are heat sealajble. The original coatings developed in the 1920's and 1930's were based on nitrocellulose lacquers, but polyvinylidene. chloride (Saran) coatings have now been developed that are more moisture-proof and better looking.

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