ASTM D395 – Standard Test Methods for Rubber Property—Compression Set
Description:
Significance and Use
4.1 Compression set tests are intended to measure the ability of rubber compounds to retain elastic properties after prolonged action of compressive stresses. The actual stressing service may involve the maintenance of a definite deflection, the constant application of a known force, or the rapidly repeated deformation and recovery resulting from intermittent compressive forces. Though the latter dynamic stressing, like the others, produces compression set, its effects as a whole are simulated more closely by compression flexing or hysteresis tests. Therefore, compression set tests are considered to be mainly applicable to service conditions involving static stresses. Tests are frequently conducted at elevated temperatures.
Scope
1.1 These test methods cover the testing of rubber intended for use in applications in which the rubber will be subjected to compressive stresses in air or liquid media. They are applicable particularly to the rubber used in machinery mountings, vibration dampers, and seals. Three test methods are covered as follows:
| Test Method | Section |
| A—Compression Set Under Constant Force in Air | 8 – 11 |
| B—Compression Set Under Constant Deflection in Air | 12 – 15 |
| C—Compression Set Under Constant Deflection in Air Considering Material Hardness | 16 – 21 |
1.2 The choice of test method is optional, but consideration should be given to the nature of the service for which correlation of test results may be sought. Unless otherwise stated in a detailed specification, Test Method B shall be used.
1.3 Test Method B is not suitable for vulcanizates harder than 90 IRHD.
1.4 The values stated in SI units are to be regarded as the standard.
ASTM D3948