BS ISO 2921:2019

What is ISO 2921– Temperature-retraction procedure about? 

ISO 2921 specifies a method for the determination of the temperature-retraction characteristics of stretched vulcanized rubber. 

ISO 2921 does not cover thermoplastic rubbers, as many thermoplastic elastomers have a yield point in the range of 5 % to 20 % elongation. 

Who is ISO 2921– Temperature-retraction procedure for? 

ISO 2921 on adhesives is relevant to: 

• Manufacturers of vulcanized rubber 
• Chemical engineers 
• Any entity responsible for testing and quality assurance of rubber and thermoplastic 

Why should you use ISO 2921– Temperature-retraction procedure for? 

A vulcanization process involves heating rubber with sulphur, accelerator and activator at 140–160°C. 

ISO 2921 provides best practice guidance on methods and requirements for determining the low temperature characteristics for temperature retraction procedure test. 

ISO 2921 specifies a method for stretching a piece of test piece at a standard laboratory temperature and then cooling it to a sufficiently low temperature to prevent retraction upon removal of the stretching force. The stretching force is then removed and the temperature is gradually increased. 

Overall, ISO 2921 is a comprehensive guide to provide methods for determining the low temperature retraction characteristics, so users will gain a comprehensive understanding of the quality of vulcanized rubber to improve durability and strength. 

What’s changed since the last update? 

BS EN 2921:2019 supersedes BS EN 2921:2011, which is withdrawn and includes 

• In 5.8, a clarification has been included as for how to set the slight tension on the test pieces. 
• Precision results has been added as Annex B