Polyurethane , commonly abbreviated PU, is any polymer
consisting of a chain of organic units
joined by urethane
(carbamate) links. Polyurethane polymers are formed through step-growth
polymerization by reacting a monomer
containing at least two isocyanate
groups with another monomer containing at least two hydroxyl
in the presence of a catalyst.
Polyurethane formulations cover an extremely wide range of stiffness,
hardness, and densities. These materials include:
- Low-density flexible foam
used in upholstery
- Low-density rigid foam used for thermal
insulation and RTM
- Soft solid elastomers
used for gel pads and print
- Hard solid plastics used as electronic instrument bezels and structural
Polyurethanes are widely used in high resiliency flexible foam seating,
rigid foam insulation panels, microcellular foam seals
durable elastomeric wheels and tires, automotive suspension bushings,
electrical potting compounds, high performance adhesives
and sealants, Spandex
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 not produced from
ethyl carbamate, nor do they contain it.
Polyurethanes are part of a very versatile
group of materials that find uses in a wide range of applications, both domestic and industrial. Polyurethanes
are widely used in many applications such as paints and lacquers, foam mattresses, medical implants, and
industrial applications such as rollers, electrical encapsulation, engineering components, shoe soles, seals,
and in the mining industry.
are organic polymers that contain the urethane group in the structure. They are typically made by the reaction
of a polyol with a diisocyanate.
Depending on initial reaction, the final product may require the addition of
additives such as chain extenders, catalysts, and blowing agents.
By careful arrangement of the chemistry, the entire process can be
carried out in one step. Polyureas are similar in reaction to polyurethanes. They are made from polyamides and
not polyols. They contain urea groups in place of urethane groups.