Thirteen of these elastic polymers are known as conventional rubber. That means they are mixed, milled, and molded by techniques which have been in use by the rubber industry for nearly 100 years. Polyurethane is known as synthetic rubber. Its raw materials are liquid and enter molds at low pressure and are generally "cured" at the same temperature as that which they are mixed.
Polyurethanes are not plastics
Abrasion resistance of polyurethane
Field applications have proven polyurethanes provide a definite wear advantage due to its superior abrasion resistant properties. In working service, molded Polyurethane has outworn rubbers, plastics, steel, and even ceramics - often by a factor of 10 to 1.
The table below provides a comparison of the abrasion resistance of polyurethane versus various rubbers and plastics.
Polyurethane vs. metals, plastics & rubbers
|Urethane vs. Metal||Urethane vs. Plastic||Urethane vs. Rubber|
Environmental properties of polyurethane
Polyurethane Elastomers vs. Conventional Rubbers
|Environment||Polyester Elastomers||Polyether Elastomers||Natural Rubber||Neoprene Rubber||Butadiene Rubber|
|ASTM No.1 Oil||E||F||P||G||P|
|ASTM No.3 Oil||E||P||G||P||P|
e.g., 5% HNO
e.g., 5% NaOH
E=excellent G=good F=fair P=poor
Limitations of Polyurethane
In most dynamic applications we recommend staying at temperatures below 160�F (70�C). The normal, high property working range is -40�F to 160�F (-40�C to 70�C). At 160�F (70�C) the properties of the elastomer begin to show a decline. The bond between urethane and metal weakens considerably above 160�F (70�C).
Urethanes exhibit high hysteresis and low thermal conductivity. They do not dissipate heat built up by dynamic action quickly. Avoiding heat build-up in an elastomeric part is a paramount consideration in design. In practice, this is usually done by controlling the amplitude of the deflection.
Long term exposure to hot, humid environments should be avoided. Some urethanes are much more resistant than others to this type of environment.
Certain chemicals such as concentrated acids and polar solvents attack urethanes, and urethanes should not be put into continuous service in these environments.