Elastomeric polyurethane is a class of polyurethane materials with rubber properties. As polyurethane, it is a polymer derived from the reaction between molecules with isocyanate (RN=C=O) functional groups and molecules with multiple alcohol groups (R-OH), called polyols. The choice of isocyanate and polyol makes one type of polyurethane resilient over another.
Fabrication materials and coatings made of elastic polyurethane are available. In addition to being highly elastic, elastic polyurethanes also have very good abrasion resistance, tear strength, chemical resistance and broad temperature compatibility. Coatings are often used to block moisture, which in some cases can lead to adverse effects such as corrosion.
Several common types of elastomeric polyurethanes can be classified by isocyanate raw material , such as:
Toluene diisocyanate (TDI),
Diphenylmethane diisocyanate (MDI)
1,5-naphthalene diisocyanate
The physical properties of elastomeric polyurethanes vary from formulation to formulation. A broad class can include aromatic aliphatic polyurethanes, depending on whether the carbon backbone is aromatic or aliphatic. The properties of some elastomeric polyurethanes (called modified polyurethanes) change with the addition of non-reactive ingredients such as plasticizers or oils. Some formulations can even consist of blends of aromatic, aliphatic or modified polyurethanes.
Various elastic polyurethanes range in hardness from 20 Shore A to 80 Shore D. The high elasticity and tensile strength allow some materials to be stretched up to 600% in size. The material also has good compression, tear strength and resilience. Flexibility can be maintained at low temperatures, and some formulations can work in temperatures below freezing and above 80 degrees Celsius. Elastomeric polyurethane resists water absorption and is resistant to attack by oils, solvents and oxygen. However, they can be easily damaged by strong acids and certain solvents. Modified polyurethanes can also add properties such as flame retardancy and resistance to biological growth, such as fungal growth.
Elastomeric polyurethanes are used as parts when high dynamic stresses are expected. Here, the physical properties of the polyurethane can adapt to changes in shape and mechanical forces, extending the life of the part. When used as a coating, elastic polyurethanes are chosen to inhibit moisture transmission, improve aesthetics, prevent abrasion damage and increase flame retardancy.
