Polyurethane(PU, PUR)

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A polyurethane (PUR and PU) is polymer composed of a chain of organic units joined by carbamate (urethane) links.

Polyurethane polymers are formed by combining two or several bi- or higher functional monomers. One contains two or more isocyanate functional groups (with formula –N=C=O) and the other contains two or more hydroxyl groups (with formula –OH). The alcohol and the isocyanate groups combine to form a urethane linkage:

ROH + R'NCO → ROC(O)N(H)R' (R and R' are alkyl or aryl groups)
This combining process, sometimes called condensation, typically requires the presence of a catalyst. More complicated monomers are also used.

Polyurethanes are used in the manufacture of flexible, high-resilience foam seating; rigid foam insulation panels; microcellular foam seals and gaskets; durable elastomeric wheels and tires; automotive suspension bushings; electrical potting compounds; high performance adhesives; surface coatings and surface sealants; synthetic fibers (e.g., Spandex); carpet underlay; and hard-plastic parts (e.g., for electronic instruments).

Polyurethane is also used for the manufacture of hoses and skateboard wheels as it combines the best properties of both rubber and plastic.