Polyurethane
Polyurethane is a polymer. Its name is often shortened to PU or PUR. Polyurethane is made of organic units, which are joined by urethane. Polyurethane polymers are formed through step-growth polymerization. In this process, a monomer containing at least two isocyanate functional groups reacts with another monomer containing at least two hydroxyl (alcohol) groups in the presence of a catalyst.
Polyurethane is available with different levels of stiffness, hardness or densities. Examples for such materials are:
- Low-density flexible foam used in upholstery
- Low-density rigid foam used for thermal insulation and RTM cores
- Soft solid elastomers used for gel pads and print rollers
- Low density elastomers used in footwear
- Hard solid plastics used as electronic instrument bezels and structural parts
Polyurethanes are widely used in high resiliency flexible 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 and sealants, Spandex fibers, seals, gaskets, carpet underlay, and hard plastic parts.
Polyurethane products are often called "urethanes". They should not be confused with the specific substance urethane, also known as ethyl carbamate. Polyurethanes are neither produced from ethyl carbamate, nor do they contain it.
Polyurethane Media
Polyurethane synthesis, wherein the urethane groups −NH−(C=O)−O− link the molecular units
A kitchen sponge made of polyurethane foam
Otto Bayer in 1952 demonstrating his creation
synthesis of polyurethane from isocyanate and a diol
Isomers and polymer of methylenediphenyl diisocyanate (MDI)
Open-flame test. Top: untreated polyurethane foam burns vigorously. Bottom: with fire-retardant treatment.
Polyurethane foam made with an aromatic isocyanate, which has been exposed to UV light. Readily apparent is the discoloration that occurs over time.
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