Viscose / Rayon is worldwide produced with a world production of more than 4 million tons per year. The raw material is cellulose, one of the most useable natural polymers (wood pulp). In the first production step, the wood pulp is immersed in sodium hydroxide to convert it to alkaline cellulose. After pressing and shredding the alkaline cellulose is aged to depolymerize. A solution of carbon disulfide is added to form cellulose xanthate. The crumbs are dissolved in sodium hydroxide to obtain a viscous solution called “viscose”. After ripening, filtering and degassing the viscose solution is pumped under pressure through metal spinnerets submerged in a spin bath. The bath contains sulfuric acid (to acidify the cellulose xanthate), sodium sulfate (for rapid coagulation) and zinc sulfate (to cross-link the cellulose molecules). By changing various process conditions and the addition of chemicals all different kind of viscose fibers are made. The final steps are drawing, washing and bleaching.
We’ve seen how expensive silk is – for many years, chemists tried to invent artificial silk that could be mass-produced more cheaply. The first commercial production of artificial silk was in the United States in 1911. This filament fiber was named rayon in 1924.
Rayon is made of cellulose, which is a fibrous chemical found in all plants. Tree bark is made of cellulose, and so are the stringy parts of celery. Some rayon is made from linters, the short cotton fibers left on cottonseeds after ginning.
The cellulose is first chemically treated so that it becomes a liquid solution. The solution is forced through a spinneret, which resembles a high tech showerhead, and into a bath that turns it back into a solid – rayon filaments.
Properties & Uses
Although rayon was first invented as artificial silk, it can also be made to resemble cotton, linen or wool. Because rayon is made from vegetable matter, it absorbs water. But absorbing water makes rayon weak and causes the fiber to break.
Rayon is often used in fashion and home furnishings, but the fiber is also found in sanitary products, diapers, and medical supplies.
Characteristics of Rayon Fibers and Products
- A cellulosic fiber usually made from wood pulp
- First manufactured fiber. Produced in 1911 but first known as “artificial silk”
- Stretches and shrinks more than cotton
- Poor abrasion resistance (easily damaged by scraping)
- Loses strength when wet
- Highly absorbent and dyes easily
- Best to dry clean or wash carefully because of shrinkage
- Fairly expensive
- Synthetic Fibers from Petrochemicals
- Rayon first used commercially in 1911.
- Rayon is made of cellulose, which is found in all plants.
- Although the fiber was created as an artificial silk, it can also resemble cotton, linen, and wool.