/pol'ee yoor"euh thayn', -yoo reth"ayn/, n. Chem.a thermoplastic polymer containing the group NHCOO: used for padding and insulation in furniture, clothing, and packaging, and in the manufacture of resins for adhesives, elastomers, and fillers.Also, polyurethan /pol'ee yoor"euh than'/.[1940-45; POLY- + URETHANE]
* * *Any of a class of very versatile polymers that are made into flexible and rigid foams, fibres, elastomers (elastic polymers), surface coatings, and adhesives.They are produced by reacting a diisocyanate (a compound with two functional groups of the typeNCO) with a diol (a compound with two hydroxyl, orOH, groups). Foamed polyurethanes, used for insulation and mattress and upholstery filler, are made with organic compounds containing carboxyl groups, causing a reaction that liberates carbon dioxide bubbles throughout the product. Spandex fibres are highly elastic and have replaced natural and synthetic rubber fibres for many textile purposes. Polyurethane elastomers are made into auto parts, rollers, flexible molds, medical equipment, and shoe soles. Polyurethane surface coatings are applied as sealants to wood, concrete, and machine parts and as linings for tanks and pipes; moisture-curing polyurethane resin is used as a general-purpose waterproof glue.
* * *any of a class of synthetic resinous, fibrous, or elastomeric compounds belonging to the family of organic polymers made by the reaction of diisocyanates (organic compounds containing two functional groups of structure −NCO) with other difunctional compounds such as glycols. The best known polyurethanes are flexible foams—used as upholstery material, mattresses, and the like—and rigid foams—used for such lightweight structural elements as cores for airplane wings.Foamed polyurethanes result from the reaction of diisocyanates with organic compounds, usually polyesters, containing carboxyl groups; these reactions liberate bubbles of carbon dioxide that remain dispersed throughout the product. Use of polyethers or polyesters containing hydroxyl groups in preparing polyurethanes results in the formation of elastomeric fibres or rubbers that have outstanding resistance to attack by ozone but are vulnerable to the action of acids or alkalies.In textiles the synthetic fibre known generically as spandex is composed of at least 85 percent polyurethane by weight. Such fibres are generally used for their highly elastic properties. Trademarked fibres in this group are Lycra, Numa, Spandelle, and Vyrene. Such fibres have, for many textile purposes, largely replaced natural and synthetic rubber fibres.Although somewhat weak in the relaxed state, spandex fibres can be stretched about 500–610 percent beyond their original length without breaking and quickly return to their original length. The fibre, usually white with dull lustre, is readily dyed. It absorbs very little moisture. It melts at about 250° C (480° F) and yellows upon prolonged exposure to heat or light. Items made of spandex can be machine washed and dried at moderate temperatures. Use of chlorine bleach can produce yellowing. Spandex fibres are frequently covered with other fibres such as nylon.Spandex is used in such apparel as foundation garments, support hosiery, and swimsuits. It is light in weight and cool; it is resistant to deterioration from body acids; and it is easily laundered and quick-drying.
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