Does atomic oxygen have any effect on rubber O-rings?

The sealing structure of rubber O-ring is simple and reliable, so it is widely used. In aircraft and spacecraft, this kind of sealing structure is also often used. The silicone rubber of hydraulic O-rings, because silicone rubber is a high molecular polymer, the influence of various environmental conditions in space, especially atomic oxygen, on its sealing performance cannot be ignored. . The space environment of low earth orbit (LEO) is mainly composed of N₂, O₂, Ar, He, H and atomic oxygen AO (Atomic Oxygen), of which atomic oxygen accounts for the highest content of about 80 percent , as the most abundant particle in the LEO environment, Atomic oxygen is formed by the photolysis of oxygen molecules under the action of solar ultraviolet rays with wavelengths less than 243 nm. Atomic oxygen not only has strong oxidizing properties, but also when the aircraft runs in LEO at orbital speed, atomic oxygen hits the surface of the material at a relative speed of 78km/s, and the average kinetic energy of the impact material can reach 45eV, thus The change in material properties causes the sealing effect to change. Therefore, for long-term sealing that requires a small leakage rate, it is necessary to study the law of the influence of atomic oxygen on its sealing performance.

The mass of the rubber O-ring decreases after a certain time of atomic oxygen action, the longer the atomic oxygen exposure time is, the greater the mass change of the O-ring is, and the larger the exposed area of the O-ring is, the greater the mass change.

The silicone rubber 863-3-1 and silicone rubber 863-3-3 materials of the rubber O-ring, the compression rate of the O-ring in the experiment is 40 percent , and the temperature is normal temperature. The leakage rate is significantly higher than that before the action of atomic oxygen, and the longer the time of atomic oxygen action, the greater the leakage rate, and the increment is about 9. 4 percent 44. 6 percent . It can be seen that the effect of atomic oxygen on the rubber O-ring The effect of the leakage rate of the atomic oxygen is relatively large, and the combined effect of atomic oxygen and ultraviolet rays has a greater impact on the leakage rate than the effect of atomic oxygen alone.

The influence of atomic oxygen effect on the performance of rubber O-rings, the surface before atomic oxygen effect is very smooth, and there is almost no surface damage; after the small flux exposure experiment, the surface has some changes, and there are some point-like pits in a small number of places , which may be the result of the effect of atomic oxygen on silicone rubber. After the action of atomic oxygen with a large flux, the surface morphology changed greatly, from smooth to undulating and ravine-like, indicating that the time of atomic oxygen action has a greater effect on the surface morphology of the O-ring of the silicone rubber material. big impact. Especially after the combined action of atomic oxygen and ultraviolet radiation, the surface of the O-ring is not only grooved, but also has many tiny pits on the surface. Therefore, the combined effect of ultraviolet radiation and atomic oxygen has a more significant impact on the O-ring.

Atomic oxygen has a great erosion effect on the surface of the O-ring; after the O-ring is exposed to atomic oxygen, the mass decreases and the leakage rate increases significantly; the longer the exposure time, the more serious the damage to the surface morphology and the greater the reduction in mass. The more, the greater the leakage rate. The combined effect of atomic oxygen and ultraviolet light has a more pronounced effect on the leakage rate of the O-ring.