Polyurethanes (PUR)

Polyurethanes (PUR) are a group of plastics that can have different properties depending on how they are processed. So they can either be very hard and brittle, but also soft and permanently elastic. As a result, they are used in a wide variety of applications, such as foam for upholstered furniture and winter clothing, and as paints and adhesives for the manufacture of rolls and rollers.

Polyurethane, usually just referred to as PU or PUR for short, is a chemically manufactured plastic. Due to its numerous positive properties, PU is processed in countless industries; without it, many products would not even exist. Nevertheless, the substance has a reputation for being harmful to human health. In fact, PU is made from isocyanate, which is toxic to humans. However, this only applies to the manufacturing process. When hardened, PU is harmless to humans.

Polyurethane properties

PU is particularly popular because of two distinctive properties: PU is both insulated and flexible. Used as polyurethane foam in mattresses, it adapts individually to every body shape. The material is also used in protective suits to protect the wearer from the cold. Another property: Due to its flexibility, PU not only adapts well everywhere. The plastic is also very light compared to other materials. For this reason, PU is often installed in cars. The advantage: The vehicle is lighter overall and consumes less fuel.

Products that can be made from polyurethanes 

Whether clothing, furniture, paints and adhesives or accessories for cars: PU is a substance that can be used individually and in a variety of ways. The material is found in cars, furniture, shoes and many other items.

PU is used in numerous industries. In construction, for example, PUR foam is used to seal joints, stabilize foundations or seal windows, as well as for thermal insulation. PU as an elastomer is often used in the textile industry for textile fibres. The upholstery of numerous pieces of furniture are also made of PU foam panels. Polyurethane glue, in turn, is great for gluing wood. A polyurethane coating is found in the interior of most automobiles. Even in the household, the material has become indispensable. Commercial household sponges are usually made of PU foam. Polyurethane varnishes are used for varnishing. Whether for the automotive or industrial industry: Polyurethane paint is used for painting in numerous industries. Last but not least: Polyurethane resin is used for potting compounds.

PU material and properties

PU is a plastic that is used in a wide variety of areas. The reason is obvious: The material is characterized by its special properties. These include, among others:

• very high mechanical strength
• very good temperature resistance
• extremely wear-resistant
• good damping values
• resistant to oils and fats

For this reason, PU is often used as a technical construction material. However, PU is also often used in the painting industry. PU acrylic paint is a PU-reinforced paint that is ideal for protective and well-covering paintwork. The easy-to-process PU acrylic paint is suitable for indoor and outdoor use, dries comparatively quickly and is characterized by a high surface hardness.

Pure material and properties

Polyurethanes are formed by reacting diols or polyols with polyisocyanates. They are usually simply referred to as PU; their DIN abbreviation is PUR. Depending on the manufacturing process, these can be hard and brittle or soft and flexible. If PUR is foamed, it is known as construction foam. The density of unfoamed PUR varies between 1,000 and 1,250 kg/m3.

PU Plastic

PU plastic is made from the raw materials isocyanate and polyol using the high-pressure or low-pressure process. In the high-pressure process, this happens at a pressure of between 200 and 300 bar. With the low-pressure process, on the other hand, the pressure is only a maximum of 40 bar. The disadvantage of the low-pressure process is that is has longer reaction times. Therefore, the parts cannot be further processed immediately.

PUR Plastic

PUR plastic can be useful for various areas of application. In the form of flexible foam, the PUR foam is used for seat cushions, upholstered furniture and car seats, among other things. It is also a perfect raw material for mattresses. These are available in different degrees of hardness. PU hard foam, on the other hand, is used in construction. Specially prefabricated polyurethane panels are used, among other things, to insulate walls and ceilings. The advantage of the panels compared to other materials: They can be easily processed with standard tools. The PU sealant is also indispensable in the construction industry: Such a PU sealant is indispensable for bonding of all kinds in structural and civil engineering. Due to its very high weather resistance, the fabric is ideal for visible joints. The easy-to-use sealant also hardens without bubbles and can therefore also be used by laypeople. A PU floor coating is also the choice of numerous tradesmen: For these, polyurethane resin is used as the last layer for sealing, which perfectly protects every surface.

Differences between pur ester and pur ether

PU is created by a so-called polyaddition. Depending on the starting materials used for production, a distinction can be made between PUR based on ester and PUR based on ether. Ester (polyol) has a very high mechanical strength, is extremely wear-resistant and scores with good damping values. In addition, the material is resistant to oils and fats and has very good weather resistance. The cold-flexible material is characterized by low permanent deformation. Ether (polyol), on the other hand, is resistant to hydrolysis, flexible when cold down to minus 50 degrees Celsius and resistant to microbes.

How dangerous is polyurethane for people?

PU is made from isocyanate. This substance is toxic to humans. During its processing, polyurethane foam is actually hazardous to health. During processing, care must therefore be taken to wear personal protective equipment, i.e. gloves and safety goggles. However, once the foam has hardened, it no longer poses a health risk. Even if PU is used in the food sector, the Federal Institute for Risk Assessment has clearly stated that the substance does not pose a risk. Only thermal PU can contain plasticizers that can be harmful to health.

Is polyurethane plastic?

PU is a chemically manufactured plastic. The collective term plastic covers all conceivable plastics, with polyethylene being the best known. However, PU is also considered plastic.
 

What material is polyurethane?

Polyurethane is one of the plastics or synthetic resins. Depending on how the material is manufactured, three different types of plastic can be distinguished: thermoplastics, duroplastics and elastomers. This is why PU can be used in so many different ways and in a wide variety of areas.

Is polyurethane recyclable? 

PU is not only versatile, but also recyclable. Mechanical as well as chemical and raw material recycling are possible. PU can easily be reused, for example as an underlay for a carpet. The PU can also be used as a raw material for incineration plants; this is referred to as energy recovery. But what should be considered when disposing of PU? PU insulation material waste is not classified as hazardous and can therefore be disposed of with household waste without any problems.

Last but not least: PU can help conserve our earth's natural resources. PU coatings and paints, for example, help to significantly increase the service life of a product. As an insulating material, PU helps to save energy and the vehicle bodies, which are lighter thanks to PU, ensure lower fuel consumption.

• PU recycling
• PUR recycling plants