There are many factors that affect the age of silicone rubber products.Today, I will introduce the main points.
1, the role of heat, increase the temperature can cause thermal cracking or thermal crosslinking of silicone rubber products. But the basic role of heat is activation. Increasing the rate of oxygen diffusion and activating the oxidation reaction, thereby accelerating the oxidation rate of the rubber, is a ubiquitous phenomenon of aging - thermal aging.
2, the role of oxygen, oxygen in the rubber with the rubber molecule free radical chain reaction, molecular chain breakage or excessive cross-linking, resulting in changes in the properties of silicone rubber products. Oxidation is one of the important reasons for rubber aging.
3, the reason of 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. The external light acts as a heating. Another characteristic of light action (unlike 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".
4. The role of ozone, the chemically active oxygen of ozone is much higher and more destructive. It also causes the molecular chain to break, but the effect of ozone on silicone rubber products 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.
5, the role of water, the role of water has two aspects: silicone rubber products in the humid air rain or soaked in water, easy to break, this is because the water-soluble substances in the rubber and water and other ingredients are extracted by water Dissolved. Caused by 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.
6. The action of mechanical stress, under the repeated action of mechanical stress, will break the rubber molecular chain to form free enthalpy, trigger 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.
7, other reasons for silicone rubber products aging are chemical media, variable metal ions, high-energy radiation, electricity and biology.
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