Rayon—The Multi-Faceted Fiber
Of all the fibers, rayon is probably the most perplexing to consumers. It can be found in cotton-like end uses, as well as sumptuous velvets and taffetas. It may function successfully in absorbent hygiene and incontinence pads and equally well-providing strength in tire cords.
What is Rayon that has so many faces?
Rayon was the first manufactured fiber. It was developed in France in the 1890s and was originally called “artificial silk.” In 1924, the term rayon was officially adopted by the textile industry. Unlike most man-made fibers, rayon is not synthetic. It is made from wood pulp, a naturally-occurring, cellulose-based raw material. As a result, rayon’s properties are more similar to those of natural cellulosic fibers, such as cotton or linen, than those of thermoplastic, petroleum-based synthetic fibers such as nylon or polyester.
Although rayon is made from wood pulp, a relatively inexpensive and renewable resource, processing requires high water and energy use and has contributed to air and water pollution. Modernization of manufacturing plants and processes combined with the availability of raw materials has increased rayon’s competitiveness in the market.
At one time, rayon and cotton competed for similar end uses. Although rayon is a relatively inexpensive fiber, cotton prices are considerably lower, giving it a competitive advantage over rayon. Rayon’s versatility as a fiber and relatively low cost have increased its use in blending, but also encouraged its use in lower quality fabrics and garments—the performance of which has sometimes tarnished the image of rayon. Rayon’s many desirable properties, however, have made it a choice for some designer and high-end apparel.
Types of Rayon
There are four major types of modifications of rayon. Understanding each type should help clarify differences in product performance. “Regular rayon” has the largest market share. It is typically found in apparel and home furnishings and identified on labels by the term “viscose.” The distinguishing property of regular rayon is its low wet strength. As a result, it becomes unstable and may stretch or shrink when wet. Dry cleaning is usually recommended to preserve the appearance of fabrics made from this fiber. If machine washed, untreated regular rayons can shrink as much as 10 percent.
High Wet Modulus (HWM) rayon is a modified viscose that has virtually the same properties as regular rayon, plus high wet strength. HWM rayons can be machine washed and tumble dried and perform much like cotton to similar end uses. HWM rayons can also be mercerized, like cotton, for increased strength and luster. The terms frequently used to describe HWM rayon in apparel includes “polynosic” rayon or the trade name MODALTM.
High Tenacity Rayon is a modification of “regular rayon” to provide exceptional strength (two times that of HWM rayon). High tenacity rayon is primarily found in tire cord and industrial end uses. It may be finished, chemically coated, or rubberized for protection from moisture and potential loss of dimensional stability and strength during use.
Cuprammonium Rayon is another type with properties similar to those of viscose or regular rayon. The manufacturing process differs somewhat from that of regular rayon and is less environmentally friendly. As a result, cuprammonium rayon is no longer produced in the United States.
Other types of rayon have been developed for specialized end uses. These include disposable, non-woven markets, and high-absorption rayon fibers with moisture-holding properties for disposable diapers, hygiene, and incontinence pads, as well as medical supplies. Microfibers are not a type of rayon, but rather a very fine fiber that can be manufactured from either regular or HWM rayons. Microfibers are generally less than one denier in diameter. A denier is about one-half the thickness of a fine silk fiber. Most fine rayons are 1.1 to 1.5 denier. Rayon microfibers have been successfully produced at 0.9 deniers. Fabrics from microfibers are very drapable and silk-like in hand and appearance. Those made from HWM rayons will be machine washable, while those made from regular rayons will require dry cleaning or very gentle hand-washing.
Currently, two major companies manufacture rayon fiber for U.S. markets. According, a British company, manufactures viscose rayon in short staple lengths and microfibers. Lenzing, based in Austria, produces viscose rayon, high wet modulus or polynosic rayon, microfibers, and long filament fibers which are used in linings and dress fabrics like taffeta. Lenzing is the only company currently manufacturing rayon in the United States. Overall, rayon is manufactured primarily in Europe and Japan.