Rayon, viscose

Rayon is a generic name for a group of fabrics made from cellulose. Cellulose is a structural component of plants. For the purpose of textile production, wood pulp from trees is the main source of cellulose.  There are several different manufacturing processes, which yield rayon types called viscose, cuprammonium, high wet modulus (modal) and lyocell.

Rayon was the first man-made fiber. One part of the process, the extraction of cellulose from the inner bark of a tree, was achieved by the Swiss chemist Georges Audemars in 1855. In 1884, Frenchman Hilaire de Chardonnet developed a nitrocellulose process for creating the fiber—a process which involved exposing cellulose to nitric acid. Nitrocellulose could then be extruded, through a tiny hole, as a filament fiber. The fiber was expensive and dangerous to make—as evidenced by the number of early factories that blew up processing the highly flammable nitrocellulose. This earliest incarnation of rayon was called Chardonnet silk.

The much safer cuprammonium process was developed by the Bemberg Company of Germany in 1890. In this process, cellulose from purified wood pulp is exposed to a solution of copper and ammonia (cuprammonium), converting the cellulose to a liquid form. After spinning and washing, the cellulose is regenerated into a filament form. This process yields a smooth, fine filament fiber. Bemberg Italy still makes this fiber, under the trademark name Bemberg. Cupro is the generic name often used for rayon produced by the cuprammonium method.

In 1892, the viscose process was patented in Britain by Charles Frederick Cross and his partners. Unlike cuprammonium, viscose rayon does not require lignin-free (purified wood pulp) cellulose, making it cheaper and more practical to produce. This process, which takes place in many stages, allows for more modifications to the fiber. Soon after its patent—and to this day—the viscose method has been the principal method used for making rayon.

The viscose rayon fiber, first known as artificial silk, was in commercial production by 1905 in Britain. In 1909, because of high import tariffs, the British company Samuel Courtauld and Co. Ltd. obtained the rights to produce rayon using the viscose process in the United States. The first U.S. rayon plant, in Marcus Hook, Pennsylvania, was in business by 1910. Courtauld called this new venture the American Viscose Company.

The multistage viscose process follows a progression that changes wood pulp into a viscose substance, then into a filament fiber. It is a very versatile process. Viscose rayon can be blended with any other fiber, and the finished textile can be soft and silky or sturdy and strong. It can have a dull or bright finish, and can be silken, linen-like or even wool-like. It takes dye well. Its clothing uses range from delicate lingerie to heavy coats. The 1930s saw the first use of staple fiber rayon, allowing rayon to not only emulate the silk that inspired it, but also cotton.

The name rayon (“beam of light” in French) was first used in 1924 in the U.S., whereas viscose was used as the name of the process and the cellulosic liquid from which the rayon was made. In Europe, viscose was adopted as the name of the fabric itself (with the name rayon disappearing after the 1970s). The U.S. Federal Trade Commission now considers viscose an alternative name for rayon.

Viscose rayon’s biggest practical weakness is its lack of strength when wet. High Wet Modulus (HWM) or modal rayon was developed in the 1950s; it is a variation of viscose rayon which makes for a stronger fiber.

Lyocell was developed starting in the late 1970s by Courtaulds Fibres UK, and first manufactured in 1987. It differs in production from viscose rayon in that the solvent is reused, reducing its environmental impact (a major problem with older rayon processes). Tencel was the first trade name used for the staple fiber lyocell in North America, dating from 1992. Lyocell is also spun into filament fibers for silk-like textiles.