Additional mechanical requirements should be specified only where necessary. They can be specified simply by description e.g. “good tear resistance required” or quantified by the use of a defined test method (such as ASTM or BS test methods) giving maximum or minimum values as appropriate. These values may be obtained by calculation based on the actual requirements of the application, by comparison with known values for similar applications or materials, or by testing a material which has been proved satisfactory by trial or experiment.

Where requirements are considerably more complex than the scope of this publication, the ASTM or BS framework for specifying rubber materials can be consulted. Materials may also be selected from the BS range of standard and special application specifications, some of which are listed below.

If the properties required of the rubber are difficult to determine, the production of a prototype mould should be considered. A variety of rubber compounds can then be moulded and parts tested for suitability in the actual application. Once a material has been proved suitable, it can be tested and its properties appropriately defined.