Adhesion of an Elastomer Seal to Metal and its Mitigation with Atomic Oxygen Pretreatment

摘要

Silicone elastomer compounds are a reliable option for gas pressure seals used in space applications. Seals fabricated from these compounds effectively meet typical leak rate, compression force, and outgassing requirements. One negative characteristic of silicone elastomer compounds use in space applications, however, is their adhesive tendency. When configured in the face-seal orientation of a reusable docking seal, an elastomer seal needs to readily release from its mating counter-face. Elevated adhesion between a seal on one spacecraft and its counter-face on a mating spacecraft is unacceptable, as it may damage or remove the seal, cause an uneven release between the two vehicles, or prevent undocking from occurring altogether. To characterize the adhesion of a candidate docking seal, a subscale silicone elastomer seal assembly was evaluated at -50°C, 23°C, and 75°C. Tests showed that adhesion between the seal and its counter-face was greatest at -50°C, at an unacceptably high 1.4 kN. To investigate a potential mitigation technique, additional seal assemblies were exposed to different levels of atomic oxygen (AO) fluence, and then evaluated at -50°C for comparison to results from tests of the untreated assembly. AO pretreatment of 1.3 × 10~(20) atoms/cm~2 showed a complete mitigation of adhesion. In addition, the durability of the surface pretreatment was verified by completing over 150 simulated docking-undocking cycles.