cellophane

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cellophane,

thin, transparent sheet or tube of regenerated cellulosecellulose,
chief constituent of the cell walls of plants. Chemically, it is a carbohydrate that is a high molecular weight polysaccharide. Raw cotton is composed of 91% pure cellulose; other important natural sources are flax, hemp, jute, straw, and wood.
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. Cellophane is used in packaging and as a membrane for dialysisdialysis
, in chemistry, transfer of solute (dissolved solids) across a semipermeable membrane. Strictly speaking, dialysis refers only to the transfer of the solute; transfer of the solvent is called osmosis.
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. It is sometimes dyed and can be moisture-proofed by a thin coating of pyroxylinpyroxylin
, partially nitrated cellulose (see nitrocellulose). It is used in lacquers, plastics, and artificial leathers. Pyroxylin lacquers are made by dissolving pyroxylin in a mixture of volatile solvents and adding a plasticizer and a pigment or dye.
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. There are several steps in the preparation of cellophane from raw cellulose. The cellulose is first treated with an alkali, e.g., sodium hydroxide, and mixed with carbon disulfide to form viscose (see viscose processviscose process
, method widely used for the commercial preparation of rayon. Cellulose, prepared from either wood pulp or, less commonly, cotton linters, is treated with sodium hydroxide (an alkali) and then with carbon disulfide, the resulting product being a substance called
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). The viscose is aged for several days and then forced through a straight or circular slit into a dilute acid solution. The dissolved cellulose precipitates, and this regenerated cellulose has a lower molecular weight and a less orderly structure than the cellulose from which it is formed.

Cellophane

 

a thin, transparent, sheet material obtained from viscose (see alsoHYDRATED CELLULOSE FILMS). It is mainly used as a packaging material and as an artificial casing for sausage products.

cellophane

[′sel·ə‚fān]
(materials)
A thin, transparent sheeting of regenerated cellulose; it is moisture-proof, and sometimes dyed, and used chiefly as food wrapping or as bags for dialysis.