Ozone aging and protection of rubber products

Update:19-01-2019
Summary:

Ozone is an important factor in the aging of rubber pro […]

Ozone is an important factor in the aging of rubber products in the atmosphere. Ozone is more active than oxygen, so its attack on rubber, especially unsaturated rubber, is much more severe than oxygen.
The ozone (o3) in the atmosphere is decomposed by the absorption of short-wave ultraviolet light in sunlight by oxygen molecules.
The oxygen atom is recombined with oxygen molecules. There is a layer of ozone with a concentration of about 5×10—in the space of 20~30km from the surface of the earth. With the vertical flow of air, ozone is brought to the surface of the earth, and the concentration of ozone gradually decreases from high to high. In addition, ozone is generated in places where ultraviolet light is concentrated, in discharge places, and in electric motors, especially where electric sparks are generated. Usually the concentration of ozone in the atmosphere is 0~5X10-8. The concentration of ozone varies from region to region; the concentration of ozone varies from season to season. Although the concentration of ozone near the ground is very low, the damage to rubber cannot be ignored.
Unsaturated rubber is prone to ozonation and its appearance after ozonation. Unlike thermo-oxidative aging, the ozonation of rubber products is only carried out on the surface layer contacted by ozone. The whole ozonation process is carried out by the surface. The second is that the rubber reacts with ozone to form a silver-white hard film (about lOnm thick). Under static conditions, the film can prevent deep contact between ozone and rubber, but under dynamic strain conditions or under static tension, when rubber When the elongation or tensile stress exceeds its critical elongation or critical stress, the film will crack, allowing the ozone to contact the new rubber surface, continue to ozonize and cause the crack to grow, and after the crack appears Since the base has stress concentration, it is easier to deepen the crack and form a crack. The direction of the crack is perpendicular to the direction of the stress. Generally, only a small amount of cracks appear under a small strain (such as 5%), and the crack direction is clearly discernible. When the rubber is subjected to multiple directions, it is difficult to distinguish the crack direction.

Details: auto rubber parts