There are several fibres made from the naturally occurring polymer cellulose, which is present in all plants. Mostly cellulose from wood is used to produce the fibres but sometimes cellulose from short cotton fibres, called linters, is the source. By far the most common cellulosic fibre is viscose fibre.
Viscose is defined by BISFA as being "a cellulose fibre obtained by the viscose process". It is known as rayon fibre in the USA. Although several cellulosic fibres had been made experimentally during the 19th century, it was not until 1905 that what has become the most popular cellulosic fibre, viscose, was produced.
Viscose fibres are made from cellulose from wood pulp. The cellulose is ground up and reacted with caustic soda. After an ageing waiting period, the ripening process during which depolymerisation occurs, carbon disulphide is added. This forms a yellow crumb known as cellulose xanthate, which is easily dissolved in more caustic soda to give a viscous yellow solution. This solution is pumped through a spinneret, which may contain thousands of holes, into a dilute sulphuric acid bath where the cellulose is regenerated as fine filaments as the xanthate decomposes.
Properties and End-Uses
Viscose fibres, like cotton, have a high moisture regain. It dyes easily, it does not shrink when heated, and it is biodegradable. It is used in many apparel end-uses, often blended with other fibres, and in hygienic disposables where its high absorbency is of great advantage. In filament yarn form it is excellent material for linings. It is used very little in home furnishing fabrics but in the industrial field, because of its thermal stability, a high modulus version is still the main product used in Europe to reinforce high speed tyres.