ASTM D395-16 pdf free download.Standard Test Methods for Rubber Property- Compression Set.
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. Two test methods are covered as follows:
3. Summary of Test Methods
3. 1 A test specimen is compressed to either a deflection or by a specified force and maintained under this condition for a specified time and at a specified temperature.
3.2 The residual detrmation of a test specimen is measured 30 mm after removal from a suitable compression device in which the specimen had been subjected for a definite time to compressive detbrmation under specified conditions.
3.3 After the measurement of the residual deformation, the compression set, as specified in the appropriate test method, is calculated according to Eq 1 and Eq 2.
4. Significance and Use
4. 1 Compression set tests are intended to measure the ability ot rubber compounds to retain elastic properties after pro— longed 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. Thereflre. compression set tests are considered to be mainly applicable to service conditions involving static stresses. Tests are frequently conducted at elevated temperatures.
5. Test Specimens
5.1 Specimens from each sample may be tested in duplicate (Option 1) or triplicate (Option 2). The compression set of the sample in Option 1 shall be the average of the two specimens expressed as a percentage.
5.2.2 When cutting the standard specimen, the circular die having the required inside dimensions specified in 5.2.1 shall be rotated in a drill press or similar device and lubricated by means of a soap solution. A minimum distance of I 3 mm (0.5 1 in.) shall be maintained between the cutting edge of the die and the edge of the slab. The cutting pressure shall be as light as possible to minimize cupping of the cut edges. The dies shall be maintained carefully so that the cutting edges are sharp and free of nicks.
5.3 An optional method of preparing the standard specimen may be the direct molding of a circular disk having the dimensions required 11w the test method used and specified in 5.2.1.ASTM D395 pdf download.