Long-time stress relaxation of a filled elastomer in vacuum environments

Samples of a filled elastomeric ablative material were stored at 45°C and ca. 10−6 torr for 7 months. Their tensile stressrelaxation modulus at constant strain was measured throughout the 7 months. Results of the testing are discussed primarily by comparisons of the data to atmospheric‐pressure moduli (determined in this work for shorter periods of time) and with moduli predicted from short‐time testing. Confirmation of the strengthening effects of vacuum on this composite were obtained. The use of time‐temperature superposition techniques as an approximate accelerated testing procedure for this material under these conditions was also verified.