Although not classified under SIC 22, man-made fiber production is briefly discussed in the following paragraphs to describe the upstream processing of textiles. Man-made fibers include 1) cellulosic fibers, such as rayon and acetate, which are created by reacting chemicals with wood pulp; and 2) synthetic fibers, such as polyester and nylon, which are synthesized from organic chemicals.
Since man-made fibers are synthesized from organic chemicals, yarn formation of man-made fibers does not involve the extensive cleaning and combing procedures associated with natural fibers. Man-made fibers, both synthetic and cellulosic, are manufactured using spinning processes that simulate or resemble the manufacture of silk. Spinning, in terms of man-made fiber production, is the process of forming fibers by forcing a liquid through a small opening beyond which the extruded liquid solidifies to form a continuous filament.
Following spinning, the man-made fibers are drawn, or stretched, to align the polymer molecules and strengthen the filament. Man-made filaments may then be texturized or otherwise treated to simulate physical characteristics of spun natural fibers. Texturizing is often used to curl or crimp straight rod-like filament fibers to simulate the appearance, structure and feel of natural fibers. (For more information on the synthesis of man-made fibers, refer to the EPA Industrial Sector Notebook on Plastic Resins and Man-made Fibers.)
Spun yarns are created using man-made fibers that have been cut into staple-length fibers. Staple-length fibers are then used to process fibers on wool or cotton-system machinery. Methods for making spun yarn from man-made fibers are similar to those used for natural fibers. Some fibers are processed as tow, or bundles of staple fibers. Fibers can also be produced as filament yarn, which consists of filament strands twisted together slightly. In mills, filament fibers are wound onto bobbins and placed on a twisting machine to make yarn. Filament yarns may be used directly to make fabric or further twisted to the desired consistency. Man-made filaments often require additional drawing and are processed in an integrated drawing/twisting machine. Man-made filaments are typically texturized using mechanical or chemical treatments to impart characteristics similar to those of yarns made from natural fibers.