Definition - What does Elastomeric Polyurethane mean?
Elastomeric polyurethane is a class of polyurethane material that has the characteristics of rubber. Being a polyurethane, it is a polymer derived from the reaction between a molecule with an isocyanate (R-N=C=O) functional group and a molecule with multiple alcohol groups (R-OH), called a polyol. The choice of isocyanate and polyol are what makes one polyurethane elastomeric rather than another type of polyurethane.
Manufactured materials and coatings made from elastomeric polyurethane are available. Besides being highly elastic, elastomeric polyurethanes tend to have great abrasion resistance, tear strength, chemical resistance and wide temperature compatibility. Coatings are typically used to block moisture, which in certain circumstances can lead to detrimental effects such as corrosion.
Corrosionpedia explains Elastomeric Polyurethane
A few common types of elastomeric polyurethanes can be classified by the isocyanate starting material, such as:
- Toluene diisocyanate (TDI),
- Diphenylmethane diisocyanate (MDI)
- 1,5-Naphthylene diisocyanate (NDI)
The physical properties of an elastomeric polyurethane vary greatly from one formulation to another. Broad types may include aromatic of aliphatic polyurethanes, depending on whether or not the carbon backbone is aromatic or aliphatic. The properties of some elastomeric polyurethanes, called modified polyurethanes, are altered with the addition of non-reactive components such as plasticizers or oils. Some formulations may even be composed from a mixture of aromatic, aliphatic or modified polyurethane.
The hardness of various elastomeric polyurethanes may range from 20 shore A to 80 shore D. High elasticity and tensile strength can allow for some materials to be able to elongate to 600% in size. Materials also have good compression, tear strength and resilience properties. Flexibility can be retained at low temperatures and some formulations can operate in temperatures ranging from below zero degrees Celsius and above 80 degrees Celsius. Elastomeric polyurethanes resist the absorption of water and can resist attack by oils, solvents and oxygen. They may be prone to damage by strong acids and certain solvents, however. Modified polyurethanes may also add properties such as flame resistance and prevention of biological growth, such as fungal growth.
Elastomeric polyurethanes are used as parts when a high degree of dynamic stress is anticipated. Here, the physical properties of the polyurethane accommodate a change in shape and mechanic forces, allowing for part longevity. When used as a coating, elastomeric polyurethanes are chosen for inhibiting moisture transmission, increasing aesthetics, preventing abrasion damage and possibility adding flame resistance.