Cellophane
Cellophane is a thin, transparent sheet made of processed cellulose. Cellulose fibres from wood or cotton are dissolved in alkali to make a solution called viscose, which is then extruded through a slit into an acid bath to reconvert the viscose into cellulose. A similar process, using a hole instead of a slit, is used to make a fibre called rayon.
Cellophane's impermeability to air, grease and bacteria makes it useful for food packaging.
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 self-adhesive tapes (Sellotape and Scotch Tape), a semi-permeable membrane in certain types of battery, and as a release agent in the manufacture of fibreglass and rubber products.
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