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RAYON F.T.C. Definition: A manufactured fiber composed of regenerated cellulose in which substituents have been replaced not more than 15% of the hydrogens of the hydroxyl group. Rayon is manufactured from cellulose pulp sheets, usually wood pulp, but it can be made from other sources such as cotton linters or other vegetable fibers. The pulp sheets are steeped in a caustic soda solution which removes undesirable components and also converts the cellulose to alkali cellulose. The alkali cellulose sheets are then shredded into "crumb" and aged for a definite period of time at a constant temperature. The crumb is then loaded into a dissolver and carbon disulfate added which forms cellulose xanthate, a bright orange fluffy material. Caustic soda solution is added to the dissolver which dissolves the xanthate and makes the thick, orange colored viscose spinning solution. The spinning solution is then aged until it has the optimum molecular weight (as measured by viscosity), then it is pumped through a spinneret into a bath of concentrated sulfuric acid. The acid neutralizes the alkali caustic viscose solution causing the viscose to precipitate out, forming the fiber. Byproducts formed in this reaction are sodium and zinc sulfates which must be continuously removed from the acid spin bath in a separate purification department. The wet, soft fiber is then passed over a series of godets or pulleys where it is stretched to align the cellulose chains and give the fiber strength, washed and neutralized, sometimes given a relaxation step to reduce thermal shrinkage of the fiber, coated with a spin finish lubricant, then dried on steam heated metal reels and usually given a twist and wound up on spools. PHYSICAL CHARACTERISTICS OF RAYON
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