Factors of rubber aging

In the process of processing, storage and use of rubber and its products, due to the comprehensive action of internal and external factors, the physical and chemical properties and mechanical properties of rubber gradually deteriorate, and finally lose their use value. This change is called rubber seals aging. On the surface, it is manifested as cracks, stickiness, hardening, softening, chalking, discoloration, and mildew growth. So what are the factors that affect the aging of rubber? Oxygen: Oxygen undergoes free radical chain reaction with rubber molecules in rubber, and the molecular chain is broken or excessively cross-linked, resulting in changes in rubber properties. Oxidation is one of the important reasons for rubber aging. Moisture: The effect of moisture has two aspects: rubber is easily damaged when exposed to rain in humid air or immersed in water. This is because the water-soluble substances and water-soluble substances in rubber seals are extracted and dissolved by water. Caused by hydrolysis or absorption. Especially under the alternating action of water immersion and atmospheric exposure, the destruction of rubber will be accelerated. But in some cases, moisture does not damage the rubber, and even has the effect of delaying aging. Ozone: The chemical active oxygen of ozone is much higher and 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 used on deformed rubber (mainly unsaturated rubber), cracks appearing in the direction of stress action, the so-called“ozone cracking”; When acting on deformed rubber, only oxide film is formed on the surface without cracking. Heat: Increasing the temperature can cause thermal cracking or thermal crosslinking of rubber. But the basic effect of heat is activation. Improve the oxygen diffusion rate and activate the oxidation reaction, thereby accelerating the oxidation reaction rate of rubber, which is a common aging phenomenon——Thermo-oxidative aging. Mechanical stress: Under the repeated action of mechanical stress, the rubber molecular chain will be broken to form free gluten, which will trigger an oxidation chain reaction and form a mechanochemical process. Mechanical scission of molecular chains and mechanical activation of oxidation processes. Which one can prevail depends on the conditions it is in. In addition, it is easy to cause ozone cracking under the action of stress. Light: The shorter the light wave, the greater the energy. The damage to the rubber is the ultraviolet rays with higher energy. In addition to directly causing the rupture and cross-linking of the rubber molecular chain, ultraviolet rays generate free radicals due to the absorption of light energy, which initiates and accelerates the oxidation chain reaction process. The external light plays a role in heating. Another characteristic of light action (different from heat action) is that it mainly occurs on the surface of rubber. Samples with high glue content will have network cracks on both sides, which is the so-called“photospinal fissure”. Others: Factors affecting rubber include chemical media, variable valence metal ions, high-energy radiation, electricity and biology. Company website: https://www.orksealing.com/
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