Cellulose Fibers, Regenerated

Abstract Fibers manufactured from cellulose are either derivative or regenerated; historically, they are designated man‐made fibers and distinguished from fibers based on synthetic organic polymers. A derivative fiber is one formed when a chemical derivative of a natural polymer, for example, cellulose, is dissolved and extruded as a continuous filament, and the chemical nature of the derivative is retained after the fiber formation process. A regenerated fiber is one formed when a natural polymer, or its chemical derivative, is dissolved and extruded as a continuous filament, and the chemical nature of the natural polymer is either retained or regenerated after the fiber formation process. The difficulties of making solutions of natural cellulose from which fibers can be spun has led to most fabricated cellulosic fibers being regenerated from more readily soluble derivatives of cellulose. It is the technology of making these fibers that is the subject of this article. Textile fibers and filaments composed of regenerated cellulose are called rayons. In Europe, the fibers are now generally known as viscose or lyocell; the term viscose rayon is used whenever confusion between the fiber and the cellulose xanthate solution (also called viscose) is possible. In addition to the viscose process, the cuprammonium rayon and direct dissolution–or lyocell processes are also covered. Fiber properties and environmental and commercial issues are discussed.