Ozonolysis of Elastomers
The method was used to confirm the structural repeat unit in natural rubber as isoprene. It is also a serious problem, known as "ozone cracking" where traces of the gas in an atmosphere will attack and split double bonds in susceptible elastomers, including natural rubber, polybutadiene, Styrene-butadiene and Nitrile rubber. Ozone cracking creates small cracks at right angles to the load in the surfaces exposed to the gas, the cracks growing steadily as attack continues. The rubber product must be under tension for crack growth to occur.
Ozone cracking is a form of stress corrosion cracking where active chemical species attack products of a susceptible material. Ozone cracking is a serious problem in fuel lines since cracks can penetrate the bore and cause a fuel leak, leading to fires or spillage of diesel fuel onto roads for example. Spills are especially hazardous since the slick is extremely slippery and is the cause of many road accidents, especially those involving motorcyclists. Ozone cracking was once commonly seen in the sidewalls of tires but is now rare owing to the use of anti-ozonants. Other means of prevention include replacing susceptible rubbers with resistant elastomers such as polychloroprene, EPDM or fluoroelastomers such as Viton.
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