Rubber Aging Factors

A) Oxygen: Oxygen in the rubber undergoes a free radical chain reaction with the rubber molecules, and the molecular chains are broken or excessively cross-linked, causing changes in the properties of the rubber. Oxidation is one of the important reasons for rubber aging.
B) Ozone: The chemical activity of 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 varies with whether the rubber is deformed or not. When it is used on deformed rubber (mainly unsaturated rubber), cracks appear in the direction of the stress, which is the so-called "ozone cracking"; when it is used on deformed rubber, only an oxide film is formed on the surface without cracking.
C) Heat: Increasing the temperature can cause thermal cracking or thermal crosslinking of the rubber. But the basic effect of heat is activation. Increase the oxygen diffusion rate and activate the oxidation reaction, thereby accelerating the rubber oxidation reaction rate, which is a common aging phenomenon - thermal oxygen aging.
D) Light: The shorter the light wave, the greater the energy. It is the ultraviolet rays with higher energy that destroy the rubber. In addition to directly causing the breakage and crosslinking of rubber molecular chains, ultraviolet rays can also generate free radicals due to the absorption of light energy, which initiates and accelerates the oxidation chain reaction process. External light plays a heating role. Another feature of light action (different from heat action) is that it mainly grows on the surface of rubber. For samples with high glue content, reticular cracks will appear on both sides, which is the so-called "optical outer layer crack".
E) Mechanical stress: Under the repeated action of mechanical stress, the molecular chain of rubber will be broken to generate free Tsuen, which will trigger the oxidation chain reaction and form a mechanochemical process. Mechanical breaking of molecular chains and mechanical activation of oxidation processes. Which one has an advantage depends on the conditions in which it is located. In addition, it is easy to cause ozone cracking under stress.
F) Moisture: The role of moisture has two aspects: when the rubber is exposed to rain in humid air or soaked in water, it is easy to damage, because the water-soluble substances and hydrophilic groups in the rubber are extracted and dissolved by water, hydrolyzed Or absorption and other reasons. Especially under the alternating action of water immersion and atmospheric exposure, the destruction of rubber will be accelerated. However, under certain circumstances, moisture does not damage the rubber, and even has the effect of delaying aging.
G) Oil: If it is in contact with the oil medium for a long time during use, the oil can penetrate into the inside of the rubber to cause swelling, resulting in a decrease in the strength and other mechanical properties of the rubber. Oil can make rubber swell, because after oil penetrates into rubber, the molecular diffusion occurs, which changes the network structure of vulcanized rubber.
H) Others: Factors affecting rubber include chemical media, variable valence metal ions, high-energy radiation, electricity, and biology.