The test methods defined in the ASTM D395-03 standard developed by the American Testing and Materials Organization (ASTM) cover rubber tests intended for use in applications where rubber will be exposed to pressure stresses in air or liquid medium. This standard applies especially to rubber, vibration dampers and gaskets used in machine assemblies. This standard covers the following two test methods:
The choice of one of these test methods is optional, but attention must be paid to the nature of the service for which correlation of test results is sought. Unless specified otherwise in a detailed specification, test method B is used. This test method is not suitable for vulcanizates harder than 90 IRHD (international rubber hardness rating).
Compression set is a property of general interest when using elastomers. Compression set is the amount of permanent deformation that occurs when a material is compressed to a specified deformation at a specified temperature for a specified period of time. The test method described in ASTM D395-03 requires the material to deform (compress) 25 percent over a period of time. After a recovery time of 30 minutes, the sample is measured. The resulting value is the percentage at which a material sample fails to regain its original height. For example, a 40 percent compression set states that the thermoplastic elastomer only recovers 60 percent of its uncompressed thickness. A 100 percent compression set means that the thermoplastic elastomer never gets stale. That is, the material remains compressed.
Often the creep state is confused with the compression set. However, the compression set is the amount of deformation under a constant strain. In contrast, creep is the amount of deformation under a constant stress.
Briefly, the compression set is the irreversible deformation of the material when it is released after compression. This deformation is dependent on compression strain (or compression stress), time, and temperature. In general, two test methods are used to determine this deformation: controlled deflection or controlled compression force.
Among the numerous tests, measurements, analyses, and evaluations our organization provides for businesses in various sectors, we also offer standard rubber property testing (compression set) services under the ASTM D395-03 standard, with a trained and expert staff and advanced technological equipment.
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