AU & EU – polyurethane
Cast polyurethanes can be divided into two main classes; polyester (AU) and polyether urethanes (EU). Many polyurethane elastomers are based on diphenylmethane diisocyanate (MDI). These elastomers have outstanding tensile strength, tear and abrasion resistance. They also have good resistance to oxidation, ozone, aliphatic solvents, and petroleum based fuels and oils. The electrical properties, the compression set and the creep properties are only fair and the heat resistance is poor.
The physical properties of polyester urethanes (AU) are somewhat better than those of polyether urethanes (EU); whereas EU elastomers have better chemical resistance and better low temperature flexibility but are more expensive and are sensitive to ultraviolet light. For example, polyesters can be affected by hot water, high humidity and their resistance to acids and alkalis is rather poor. They are also prone to microbiological attack. EU elastomers, on the other hand, have poor resistance to oxidation and heat.
Urethane elastomers are usually liquid cast. Tooling prices tend to be lower than those for heat and pressure molded rubbers.
COMMERCIAL AU/EU Elastomers
Manufacturers / suppliers of AU/EU elastomers are Parker, Erriks and Gallagher.
Polyurethane elastomers are used where high abrasion resistance, high strength and good oil / solvent resistance is required. Typical applications include hydraulic and reciprocating seals, gaskets, diaphragms, hoses, haul-off pads, conveyor belts, roller-skate and skateboard wheels, and many other sports goods. They are also used for abrasion-resistant coatings and linings. In all applications, consideration should be given to hydrolysis, and limited creep and heat resistance.
The typical working temperature range of AU/EU elastomers is -40°C to +90°C.