The urethane linkage (often called carbamate) is usually made by adding an OH across the C=N of an isocyanate.
The reaction is catalyzed by bases such as tertiary amines or by certain tin salts.
Polyurethanes are synthesized by the reaction of diols with diisocyanates:
Many different polyurethanes have been synthesized, giving rise to materials with widely varying properties. For example, rubbery polyurethanes are used for Spandex fiber and for seat cushions in furniture and cars, while hard polyurethanes are used for wheels on roller skates, for bowling balls, and for paints and varnishes. The hydrogen bonds between the NH and CO groups provide toughness to the polymers.
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