Cellulose is the most abundant organic chemical in the world, being the structural component of the cell wall of green plants. In terms of molecular structure, it is composed of anywhere from several hundred to over ten thousand glucose molecules linked together in a linear fashion. Cellulosic fibers from the flax plant were woven into linen as early as 8000 BC, and cotton, which has a cellulose content of over 90% was being grown, spun and woven into cloth by 3,000 BC. Around the same time, the Chinese discovered that the cocoon formed by silkworm larvae could be unraveled and used to make very fine fabrics. Wool, matted into felt, also had its origins around this time. But all of these fibers had a downside. Cotton and linen wrinkled from wear and washings, silk required delicate handling, wool shrank, was itchy and served up a meal for moths. Still, until the 19th century clothing manufacturers had to put up with such problems because there were no alternatives to the natural fibers. And then, in 1889, along came the first 鈥渁rtificial silk,鈥� later to be christened 鈥渞ayon鈥� because of the fabric鈥檚 lustery, almost metallic sheen when the rays of the sun fell upon it.
Until the late 1800s, if you wanted the luxury of silk you had better know where to find some mulberry trees infested with silkworm pupae that had wrapped themselves in a cocoon of raw silk they exuded from their salivary glands. Boiling the cocoon killed the pupae and prevented the secretion of enzymes that would normally break down the silk in order to allow the emergence of the adult in the form of the silk moth. These enzymes degrade the silk fiber from hundreds of meters in length to shorter segments, ruining it for fabric use. Some 5000 cocoons are needed to make a kilo of silk which explains why the fiber is so pricey. Although historically various attempts had been made to bypass the silkworm and convert mulberry leaves into silk, they all failed. Finally, in 1889 at the Paris Exhibition, visitors got their first glimpse of a silk-like fabric that that was washable like cotton but had the luster and delicacy of the authentic material.
Count Hilaire von Chardonnet was the inventor responsible for the marvel which was to become the first marketable synthetic fiber. Silkworms or mulberry leaves were not involved, although the Count鈥檚 interest had been spurred by his work with Louis Pasteur on silkworm diseases. He got the idea for his artificial silk by noting that collodion, the gelatinous substance formed by dissolving nitrated cellulose in a mixture of alcohol and ether, could be extruded into a fine thread. Chardonnet鈥檚 contribution was weaving the threads into fabric. Unfortunately, Chardonnet silk had one major drawback. Like all nitrocellulose products, it was highly flammable. Workmen at the textile plants where the fabric was manufactured took to calling it 鈥渕other-in-law silk.鈥�
Around the same time, across the Channel in England, Charles Cross, Edward Bevan and Clayton Beadle were working on improving the manufacture of paper and cotton thread. The general process began by treating the cellulose-containing material with sodium hydroxide (lye) to extract the cellulose. Could other chemicals be added to produce a better product, they wondered? Yes, as became apparent in 1892 when alkali cellulose was treated with carbon disulphide to form a bright orange grainy substance that formed a viscous solution when dissolved in water. Wasn鈥檛 of much use for making paper, but when this 鈥渧iscose鈥� was passed through tiny holes into an acid bath, it yielded a fiber that was still cellulose but in which the long chains of glucose molecules had been broken into shorter ones. The result was a fiber that until 1924 was commonly referred to as 鈥渁rtificial silk.鈥� That鈥檚 when the DuPont Company began to produce this regenerated cellulose on a large scale, advertising it as 鈥渞ayon.鈥� Textile manufacturers and their customers were thrilled because rayon was half the price of raw silk.
Today, rayon is widely manufactured for clothing, sheets, blankets and upholstery because it is smooth, cool and comfortable.
