Appraisal of the current standards for stress relaxation measurements in compression for rubbers

Abstract

The current British and American Standards for stress relaxation measurements in compression for rubbers are discussed in the light of results obtained with new, highly accurate equipment, which has been developed in the Institute of Polymer Technology. This work is part of a programme sponsored by the Engineering Research Station of British Gas, the Water Research Centre and the Victaulic Company PLC, and covers the development of equipment of satisfactory performance, which is suitable for commercial exploitation, and the investigation of meaningful tests for industrial use. The present paper reports work carried out to examine the test parameters which are required in the standards and, in particular, to question the specified values of some of them. Factors which have proved to be important include loading rate and temperature, whilst mechanical conditioning has been found to be less important in determining the pattern of stress relaxation. Above all, it is essential that the measurements are of sufficient accuracy, with a closely that the measurements are of sufficient accuracy, with a closely defined initial stress, for meaningful conclusions to be drawn.