ISO 6914:2008 describes three methods for the measurement of the change of stress in a test piece at a given elongation for the purpose of determining the ageing characteristics of a rubber.
- Method A is intended for measurement under continuous strain conditions.
- Method B is the preferred method for measurement under intermittent strain conditions.
In the case of both methods A and B, a stress relaxometer is used to record the stress at the temperature of ageing.
- Method C is an alternative to method B for measurement under intermittent strain conditions in which the test piece is removed from the ageing environment for measurement of the stress at standard laboratory temperature.
No agreement between the three methods should be inferred. The method used will depend on the purpose of the test.