A) 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.
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 the deformation of rubber. When it is used as a rubber for deformation (mainly unsaturated rubber), a crack which is straight in the direction of stress is generated, that is, "ozone cracking"; when it acts on a 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 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.
D) Light: The shorter the light wave, the greater the energy. What is damaging to the miscellaneous pieces of silicone rubber is the higher energy ultraviolet rays. 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. The external light acts as a heating. Another characteristic of light action (different from heat) is that it mainly grows 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".
E) Mechanical stress: Under the repeated action of mechanical stress, the rubber molecular chain will be broken to form free enthalpy, which will initiate the oxidative 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.
F) Moisture: There are two aspects to the effect of moisture: miscellaneous pieces of silicone rubber are easily destroyed when exposed to humid air or when immersed in water. This is because water-soluble substances and hydrophilic groups in the rubber are extracted by water. Caused by dissolution, hydrolysis or absorption. Especially in the alternating action of water immersion and atmospheric exposure, it will accelerate the destruction of rubber. However, under certain circumstances, moisture does not have a destructive effect on rubber, and even has the effect of delaying aging.
G) Miscellaneous pieces of silicone rubber: If it is in contact with the oil medium for a long period of time during use, the oil can penetrate into the rubber to cause swelling, resulting in a decrease in the strength and other mechanical properties of the rubber. The oil can swell the rubber because the oil penetrates into the rubber, and the molecules are mutually diffused, and the network structure of the vulcanized rubber changes.
H) Others: The chemical factors, chemical metal, high-energy radiation, electricity and biology.