This International Standard specifies a test procedure for determining the compression set characteristics of vulcanized rubbers. The test is intended to measure the ability of rubbers of hardness within the range 30 to 94 International Rubber Hardness Degrees (IRHD) to retain their elastic properties after prolonged compression at constant strain under one of the alternative sets of conditions described. With some rubbers, especially those above 85 IRHD, it may not be possible to achieve 25% compression strain. For such rubbers this method does not apply.
NOTES
1 Two sizes of test piece are described. These do not necessarily give the same values of compression set, and comparison of values obtained from the two sizes should be avoided. Where possible, the use of the large size of test piece is recommended.
2 The preparation of test pieces by either moulding or by cutting is permitted. For some types of rubber, test pieces prepared by the different methods may give different results. Where possible, the preparation of test pieces by moulding is recommended.
3 Laminated test pieces, made up of two or more superimposed disks, may also be used. These do not generally give the same values of compression set as test pieces of the same dimensions formed of one disk.