Factors Causing Rubber Aging
1. Oxygen: Oxygen undergoes a free radical chain reaction with rubber molecules in the rubber, and the molecular chain is broken or excessively crosslinked, causing a change in rubber properties. Oxidation is one of the important reasons for rubber aging.
2. The chemical activity of ozone and ozone is much higher than that of oxygen, and it is more destructive. It also breaks the molecular chain, but the effect of ozone on rubber is different depending on whether the rubber is deformed or not. When it is used as a rubber for deformation (mainly unsaturated rubber), a crack perpendicular to the direction of stress action occurs, that is, "ozone cracking"; when it acts on a deformed rubber, only an oxide film is formed on the surface without cracking.
3. Heat: Increasing the temperature can cause thermal cracking or thermal crosslinking of the rubber. But the basic role of heat is activation. Increasing the rate of oxygen diffusion and activating the oxidation reaction to accelerate the oxidation reaction rate of the rubber is a ubiquitous phenomenon of aging - thermal aging.
4. Light: The shorter the light wave, the greater the energy. What is damaging to rubber is the higher energy of ultraviolet light. In addition to ultraviolet rays directly causing the breakage and cross-linking of rubber molecular chains, rubber generates free radicals by absorbing light energy, which initiates and accelerates the oxidation chain reaction process. Ultraviolet light plays a role in heating. Another feature of light action (unlike heat) is that it mainly occurs on the surface of the oak. For samples with high gel content, there will be reticular cracks on both sides, the so-called "light outer crack".
5. Mechanical stress: The conveyor belt will break the rubber molecular chain to form a free radical under the repeated action of mechanical stress and the continuous friction process with the roller, which will initiate the oxidation chain reaction and form a force chemical process. Mechanically broken molecular chains and mechanically activated oxidation processes. Which one can prevail depends on the conditions in which it is located. In addition, it is easy to cause ozone cracking under stress.