Ozone cracking is caused by an aggressive chemical attack on a double bonded seal polymer. Elastomers with double bonds in their molecular chains are highly susceptible to ozone attack. In their free state, the polymer remains unstressed, therefore the molecular interference prevents ozone from attacking the double-bonds. However, when the polymer chains are stretched, the molecular interference is disrupted, thereby exposing the double-bonds. Once this double-bond is exposed, it reacts with ozone and breaks at this point. This is then repeated for each progressively deeper layer of polymer chains within the rubber. On the surface, this shows up as cracking in the seal. This ozone cracking permits gases and fluids to pass through in an application.
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