Bayer and his team at IG Farben invented polyurethane in 1937. However, polyurethane was not mass-produced commercially until the 1950s.
2.1. Physical properties
Appearance: PU can be transparent, translucent, or opaque, depending on its formulation. It can also be colored or pigmented.
Density: PU has a density of 1.1-1.2 g/cm3, which is slightly higher than water.
Tensile strength: PU has a tensile strength of 2.4-4.8 MPa. This makes PU a strong and durable material that can withstand high loads.
Hardness: The hardness of PU depends on its formulation, but it can range from 20 Shore A to 85 Shore D. Shore A is a measure of the softness of a material, while Shore D is a measure of the hardness of a material.
2.2. Chemical properties
PU is a very versatile material with excellent chemical resistance. It is resistant to a wide range of chemicals, including:
Acids: Most common acids, including sulfuric acid, hydrochloric acid, and acetic acid, are resistant to PU.
Bases: PU is resistant to the majority of common bases, including sodium hydroxide and potassium hydroxide.
Oils and greases: PU is abrasion, oil, and grease resistant. This makes it perfect for applications containing oil and grease, such as automotive and industrial applications.
Solvents: PU is resistant to the majority of popular solvents, including acetone and ethanol.
However, PU is not resistant to powerful oxidizing chemicals like hydrogen peroxide and nitric acid. These compounds can lead PU to degrade and lose its characteristics.
2.3. Processing properties
Polyurethane (PU) is a versatile material that can be handled via casting, injection molding, and extrusion.
Casting is a straightforward method that entails pouring liquid PU into a mold and allowing it to cure. Casting can be used to create a wide range of forms and sizes, from simple blocks to sophisticated pieces.
Injection molding is a more sophisticated procedure that includes pumping high-pressure liquid PU into a mold. Injection molding is a high-volume manufacturing process that can yield products with great precision and reproducibility.
Extrusion is the technique of driving liquid PU through a die to generate a continuous length of material. Extrusion is a technique used to make PU films, sheets, and other continuous shapes.
The appropriate processing method for a given application is determined by the desired qualities of the completed product as well as the needed production volume.