What is ISO 6914 about?
ISO 6914 discusses rubber, vulcanized or thermoplastic. The stress relaxation testing specified in ISO 6914 helps know the structural changes which occur in rubber during ageing.
ISO 6914 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.
Who is ISO 6914 for?
ISO 6914 on determination of ageing characteristics of rubber by measurement of stress relaxation in tension is applicable for:
- Manufacturing of rubber/thermoplastic
- Companies dealing with rubber, vulcanized/ thermoplastic
- Suppliers and distributors for rubber/thermoplastic
- Testing agencies of rubber material
Why should you use ISO 6914?
When a constant strain is applied to rubber, the force necessary to maintain that strain is not constant but decreases with time; this behavior is called “stress relaxation”. The process responsible for stress relaxation can be physical or chemical in nature, and under all normal conditions both types of process will occur simultaneously. However, at normal or low temperatures and/or short times, stress relaxation is dominated by physical processes, while at high temperatures and/or long times chemical processes are dominant.
Stress relaxation tests as specified in tension in ISO 6914 can be used as a measure of ageing as chemical processes will dominate in the case of a thin test piece exposed to an atmosphere containing oxygen at an elevated temperature for relatively long periods of time.
Measurements made in accordance with the methods described in ISO 6914 provide guidance about the structural changes that occur in the rubber during ageing.
What’s changed since the last update?
BS ISO 6914:2021 supersedes BS ISO 6914:2013, which is withdrawn. This fifth edition has been technically revised.