Due to the rapid development of rubber industry and car industry, the rubber is increasingly in demand. However, the aging of rubber may speed up the use and shorten the service life. The rubber products will lose the elasticity and become hard, which is not good for the usage. So we must make out what factors may cause the aging of rubber.
The oxygen in rubber will have a chain reaction of free radical with rubber molecules. The cleavage or over cross-linking of molecules chain can cause the change of rubber properties, leading to the aging of rubber. In short, oxidation is one of the most important reasons for rubber’s aging.
Compared with oxygen, the ozone is more destructive, and its chemical activity is much more higher. It also can cleave the rubber molecular chain, but the influence of ozone on rubber varies from rubber’s deformation or not. When applied to deformed rubber, the crack perpendicular to stress direction will be appeared.
The shorter is the light wave, the higher is the energy. Ultraviolet light can directly cleave the rubber molecular chain, and the rubber will produce free radical due to the absorption of light, causing and accelerating the oxidation reaction.
Increasing the temperature can give rise to the thermal cracking or thermal cross-linking of rubber. And the basic function of heating is increase the diffusion rate of oxygen and activate oxidation reaction, so as to accelerate the speed of rubber’s oxidation reaction.
5. Mechanical Stress
Under the repeated influence of mechanical stress, the rubber molecular chain will cleave and produce free radical, causing oxidation chain reaction. Besides, under the effect of mechanical stress, ozone cracking is also easily caused.
7. Oil Medium
Long-term exposure to oil can degrade the strength and mechanical property of rubber. The oil can penetrate to inside of rubber, the interdiffusion of oil molecule and rubber molecule may lead to the swelling of rubber. Therefore, the reticulate structure of vulcanized rubber will be changed.
Additionally, the chemical mediator, oxidated metal ion, high-energy radiation, electricity, biology, etc.