Rayon is a manufactured fiber produced from wood or cotton. It is widely used to make industrial materials and knit and woven textiles for clothing and decorating fabrics. Some rayon fabrics are made heat resistant and used in certain spacecraft parts.
How rayon is made.
Rayon is manufactured from the cellulose fiber of wood pulp or cotton (see Cellulose ). Various chemical processes change the cellulose into a thick liquid. This liquid is then forced through extremely small openings in devices called spinnerets to form filaments, or tiny threads. There are two chief methods for making rayon: the viscose process and the cuprammonium process.
The viscose process
is the usual method of making rayon. The process begins by soaking sheets of white pulp in a solution of sodium hydroxide. The soaked sheets are put through presses that squeeze out the excess solution. The sheets then pass through shredding machines where they are made into fine pieces called crumbs. The crumbs of cellulose are aged at high temperatures for about a day. Aging helps determine what type of yarn will be produced.
After aging, the crumbs are treated with carbon disulfide, which turns them to cellulose xanthate, a deep orange substance. Then the crumbs are dissolved in a weak solution of sodium hydroxide. This turns the mixture into viscose, a thick, molasseslike solution, which “ripens” for one to two days at a low temperature. When the solution has ripened, it is pumped to spinning machines and forced through the tiny holes in spinnerets to form filaments.
The cuprammonium process
is a method of dissolving cotton cellulose in a copper-ammonia solution. A special spinning process produces yarns of ultrafine denier, or weight.
Spinning.
All rayon-making centers on the spinneret, which contains a plate with tiny holes. Pumps force the cellulose through these holes. The threadlike cellulose then flows into a chemical bath that hardens the liquid into threads. The threads are twisted together to form rayon yarn. The yarns are woven into fabrics that look like cotton, wool, or spun silk.
Properties of rayon.
Viscose and cuprammonium rayons have much the same chemical properties. Both dye easily, and both lose their strength when wet. They regain their original strength when dry. The wet strength of rayon can be considerably improved by varying the chemical bath composition.
History.
In 1884, the French inventor and industrialist Hilaire Chardonnet patented the first practical manufactured fiber (see Chardonnet, Hilaire ). He called it artificial silk. The fiber was first commercially produced in the United States in 1910. In 1924, it was named rayon, the ray indicating the sheen of the fiber, and the on showing that it was a cottonlike fiber.
