Cindy Miller, age 15, of Wilmington, Del., for her question:
HOW DO WE GET RAYON?
Rayon is a manufactured fiber that is produced from wood pulp or cotton linters. It is used to make industrial materials and knit and woven textiles for clothing, upholstery, draperies and decorating fabrics.
Rayon is manufactured from the cellulose fiber of wood pulp or cotton. Various chemical processes reduce the cellulose to a thick liquid from which the rayon threads are made.
The liquid cellulose is forced through extremely small openings in devices called spinneretts to form filaments, or tiny threads.
There are three chief methods for making rayon: the viscose process, the cuprammonium process and the acetate process.
The viscose process is the usual method of changing wood or cotton cellulose into rayon. It starts by soaking sheets of white pulp in a solution of sodium hydroxide. After the soaked sheets are removed, they are put through the presses that squeeze out the excess solution.
Next, the sheets pass through shredding machines where they are cut into fine pieces called crumbs. The crumbs of cellulose are aged at high temperature and then combined with carbon disulfide and other chemicals to produce a molasses like solution. After aging and filtering, the solution is pumped to spinning machines.
The cuprammonium process dissolves cotton cellulose in a copper ammonia solution. A special spinning process then produces yarns of ultrafine weight.
The acetate process changes the properties of cellulose with various types of acid.
All rayon making centers about the spinneret. Pumps force the cellulose through tiny 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. To produce cottonlike yarns, the threads are cut into short lengths, then combed and twisted.
Rayon yarns are woven into fabrics that look like cotton, wool or spun silk.
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.
Acetate reacts to heat and may easily be burned when ironing. Boiling water takes out its luster. But acetate has special qualities, such as fineness, texture and dyeability, that make it desirable. It can also be treated so the material has permanent pleats.
In 1884, a French inventor and industrialist named Hilaire Chardonnet patented the first practical synthetic fiber. He called it artificial silk.
The fiber was first manufactured 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.