Rayon skin effect

Although cellulose is not thermoplastic, and rayon cannot be mechanically crimped and textured in the same way as synthetic fibers, a crimped fiber can be made by causing an imbalance in the uniformity and thickness of the skin during fiber production. Greater shrinkage of the skin in hot water, compared with shrinkage of the core, will cause the fiber to crimp. The skin effect in crimped rayon has been described by Sisson and Morehead [252]. Crimped rayon is wool like and is used alone or in blends with polyester, nylon, acetate, or wool to make carpets, upholstery, bedspreads, and clothing fabrics. 

After initial skin formation, the core of the fiber decomposes, hardens, and shrinks, causing wrinkling on the fiber skin. The final fiber cross section of viscose rayon appears serrated and irregular, and the nature of the crystallites in the skin and core will differ (Figure 3-4). This skin effect can be controlled sufficiently to give nearly round fiber cross sections where carefully controlled coagulation occurs. 

Skin contact with spilt carbon disulfide can lead to burns at the contact site. In studies that examined the harmful effects of skin contact with carbon disulfide, workers in a rayon plant who handled fibers made with carbon disulfide for more than 14 days developed blisters on their fingers. Rabbits developed blisters and ulcers on the treated areas of their ears. 

Fibers vary in cross-sectional shape, both naturally and by design. Wool fibers are essentially round and cotton fibers are elliptical. Synthetic fibers made by melt spinning can be of a desired shape. Artificial fibers that are spun from solvents in air or from an aqueous medium are usually irregular in shape because of the skin-core effect [2]. Rayon, for example, can have both regular and irregular cylindrical forms composed of hollow as well as solid fibers. 

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