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Ozone aging test chamber simulate environment to accelerate the process of rubber aging by ozone because rubber is sensitive to ozone.
Ozone mainly exists in the ozone layer below the stratosphere in the atmosphere (20 kilometers away from the surface), but there is also rare ozone in the surface atmosphere. Because of the sensitive nature of rubber materials to ozone, even thin ozone will cause cracks in all rubber products. This is due to the fact that ozone reacts with unsaturated rubber and produces a bimolecular reaction with the double bond in the rubber, and the reaction speed is very fast. The aging reaction of ozone to unsaturated rubber is carried out on the exposed surface of the rubber. After the double bonds on the surface are digested, the ozone reacts with the unsaturated bonds inside the sample.
The stretched unsaturated rubber exposed to ozone first forms ozone cracks on the surface, and then the cracks grow larger and then break. There are two views on the mechanism of rubber cracking: molecular chain breaking and surface layer destruction. In the case of a certain ozone concentration, if the mobility of the molecular chain is high, when the ozone breaks the surface molecular chain, the two ends of the break will separate from each other at a faster speed, exposing the new molecular chain at the bottom layer to continue to be attacked by ozone. Speed up the gap growth.
The cracking time of various rubbers is shortened with the increase of ozone concentration, and different rubbers have different degrees. Under the same ozone concentration, different cracks in the rubber structure grow at different speeds. Due to the different structures of NR and SBR, BR and NBR, the ozone aging characteristics are also different. Elongated NR produces cracks in a short time in the ozone environment, but the growth rate of the cracks is slow, and the number of cracks is large and shallow.
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