Other Definitions
polyurethane (dict)
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PolyurethaneA polyurethane is any polymer consisting of a chain of organic units joined by urethane links. It is used in adhesives, elastomers, foams, fibers, seals, gaskets, condoms, carpet underlayment, foam rubber, and hard parts. Production Polyurethane can be made in a variety of textures and hardnesses by varying the particular monomers used and adding other substances. Softer polyurethane can be made by adding flexible Polyethylene glycol segments between urethane links. This strategy is used to make spandex fibers, as well as foam rubber. A common method of foam rubber production involves mixing water with a liquid polyurethane, causing a chemical reaction. During the reaction Carbon dioxide is released, creating bubbles in the liquid, which then hardens to form a solid foam. This reaction forms a urea linkage -NC(O)N-, between the polyurethane molecules. Careful control of viscoelastic properties can lead to memory foam, which is much softer at body temperature than at room temperature. Uses Polyurethane is now also used in making tires. Modern roller blading and skateboarding became economical only with the introduction of tough, abrasion resistant polyurethane parts. Another common usage is found in carpentry or woodworking. A polyurethane sealant is frequently employed as a finishing coat to protect or seal wood. This use results in a hard, inflexible coat that is popular for protecting floors, but considered by some to be unsuitable for finishing antiques or other detailed pieces. Polyurethane varnish tends to de-laminate if subjected to heat or shock, leaving transparent or white patches. Because it doesn't penetrate into the wood, polyurethane also lacks the lustre of other treatments. External Links
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