87 Fatigue Crack Growth Behavior of Sealing Rubber Aged in Air and Hydrogen Gas

To elucidate the effect of aging environment on fatigue crack growth behavior of sealing rubbers, fatigue crack growth tests on unfilled sulfur-vulcanized EPDM rubbers, aged in air or hydrogen atmospheres at temperatures up to 170 °C, were performed in air at room temperature. Acceleration of fatigue crack growth rate was observed in specimens aged in air at 160 °C or higher, and the acceleration increased with increasing aging temperature. Observation of the fatigue fracture surfaces by scanning electron microscope revealed that oxidative-degradation-induced rubber structures were newly formed due to aging, causing the acceleration of fatigue crack growth rate. However, thermal aging in H₂ did not cause acceleration of fatigue crack growth rate due to the absence of oxygen.