NBN ISO 6914:2021

This document 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.
— 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.
Measurements at a single elevated ageing temperature can be used for quality control purposes
as a measure of heat-ageing resistance. Measurements at a number of temperatures can be used for
research and development purposes to estimate long-term ageing characteristics in accordance with
the procedures described in ISO 11346.
Tests under continuous and intermittent strain conditions measure the results of different processes,
and hence do not give the same results. The results of the intermittent methods B and C also cannot be
expected to be the same as they use different test conditions.