Polyurethane is a general term used for a class of polymers derived from the condensation of polyisocyanates and polyalcohols.
Polyeurothenes are are petrochemical-based derived polymer and (man) made like all the other synthetic polymers featured in this blog.
Polyurethane is made by reacting polyols and diisocyanates,
Polyols and diisocyanates are derived from crude oil and removed during the refining process just like gasoline.
Polyurethane foam can be flexible or rigid. Each form of polyurethane has many uses.
Most polyurethanes do not melt when heated but there are some (thermoplastic polyurethanes) that do.
Polyurethane formulations cover an extremely wide range of stiffness, hardness, and densities. These materials include:
Low-density flexible foam used in upholstery, bedding, and automotive and truck seating
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
Flexible plastics used as straps and bands
lining the cups of brassieres.
Carbon dioxide is used as a blowing agent to create the soft, comfortable feel of a mattress or sofa. The more blowing agent is used, the softer the resulting foam.
In rigid foams, a gas such as pentane is “trapped” in the closed cells of the foam, optimising its insulation capacity.
Rollerblade wheels, on the other hand, do not require a blowing agent and instead have a dense and hardwearing consistency.
Is polyeurothene a plastic?
this answer from Quora is a useful read
There is thermoset and thermoplastic polyurethane polymers. Both can be considered as “plastics”.
Actually “Plastics” is more a shortcut / a general public word. It refer to the fact that most of these materials have a high plasticity (ability to be permanently deform without breaking) under certain conditions. Not to a chemical composition. Specialists prefer to speak of polymers and composites.
In general language, most of common polymers compounds that can be injected/extruded are generally referred as plastics.
When it comes to Carbone/glass fiber reinforced Polyamide or to the Aramids family (including Kevlar and Grivory brands), you will rarely see the word “plastic” used because it would be devaluating for these high performance composites. Yet actually these materials can be extruded or injected quite the same way as generic plastics like PE or PP. So that these are fitting perfectly in the “plastics” category.
So that it is correct to say that thermoplastic and thermoset polymers are plastics. Including PU.
Polyurethanes are polymers. Polymers are best thought of as chains of three-dimensional structures made up of long, repeating smaller units called monomers. These monomers contain carbon, hydrogen, oxygen and nitrogen. To form the chains, the smaller links are “polymerised” or hooked together.
There are thousands of naturally occurring and man-made polymers. The first man-made polymer to be produced was Bakelite in 1909. Rayon, the first man-made fibre polymer, was developed in 1911. Other well known polymers include nylon, silicon, polyethylene, polypropylene and polystyrene.
Common polyurethane applications include:
Building insulation
Refrigerators and freezers
Furniture and bedding
Footwear
Automotive
Coatings and adhesives
Other applications read more here.
Polyurethane is the most common solvent used in modern varnishes.
Despite its xenobiotic origins, polyurethane has been found to be susceptible to biodegradation by naturally occurring microorganisms. Microbial degradation of polyurethanes is dependent on the many properties of the polymer such as molecular orientation, crystallinity, cross-linking and chemical groups present in the molecular chains which determine the accessibility to degrading-enzyme systems. Esterase activity (both membrane-bound and extracellular) has been noted in microbes which allow them to utilize polyurethane. Microbial degradation of polyester polyurethane is hypothosized to be mainly due to the hydrolysis of ester bonds by these esterase enzymes.
Isocyanates are compounds containing the isocyanate group (-NCO). They react with compounds containing alcohol (hydroxyl) groups to produce polyurethane polymers, which are components of polyurethane foams, thermoplastic elastomers, spandex fibers, and polyurethane paints. Isocyanates are the raw materials that make up all polyurethane products. Jobs that may involve exposure to isocyanates include painting, foam-blowing, and the manufacture of many Polyurethane products, such as chemicals, polyurethane foam, insulation materials, surface coatings, car seats, furniture, foam mattresses, under-carpet padding, packaging materials, shoes, laminated fabrics, polyurethane rubber, and adhesives, and during the thermal degradation of polyurethane products.
Health effects of isocyanate exposure include irritation of skin and mucous membranes, chest tightness, and difficult breathing. Isocyanates include compounds classified as potential human carcinogens and known to cause cancer in animals. The main effects of hazardous exposures are occupational asthma and other lung problems, as well as irritation of the eyes, nose, throat, and skin. https://www.osha.gov/SLTC/isocyanates/index.html