We all know that things like rubber age, so what factors can cause rubber aging?
(1) heat: increasing the temperature can cause the thermal cracking or thermal cross-linking of rubber. But the basic function of heat is activation. It is a common phenomenon of thermal oxygen aging that the oxidation rate of rubber is accelerated by increasing oxygen diffusion rate and activation oxidation reaction.
(2) light: the shorter the light wave, the greater the energy. Rubber is damaged by high - energy ultraviolet rays. In addition to the ultraviolet radiation which can directly cause the break and crosslinking of rubber molecular chain, the rubber produces free radical by absorbing light energy, and initiates and accelerates the oxidation chain reaction process. Outside light ACTS as a heating agent. Another characteristic of light (as opposed to heat) is that it develops mainly on the surface of rubber. For samples with high gel content, reticular cracks will appear on both sides, which is called "optical outer crack".
(3) oxygen: oxygen reacts with rubber molecules in free radical chain, and the molecular chain is broken or excessively crosslinked, resulting in changes in rubber properties. Oxidation is one of the important causes of rubber aging.
(4) ozone: the chemical activity of ozone is much higher than that of oxygen, which is more destructive. It also breaks the molecular chain, but the effect of ozone on rubber varies with the deformation of rubber. As used for deformation of rubber (mainly unsaturated rubber), and the direction of direct stress crack, that is, the so-called "ozone crack"; When applied to deformed rubber, only oxide film is formed on the surface without cracking.
(5) mechanical stress: under the repeated action of mechanical stress, the rubber molecular chain will break to form free chain, triggering oxidation chain reaction and forming a mechanochemical process. Mechanical fracture molecular chain and mechanical activation oxidation process. Which one wins depends on the conditions. In addition, it is easy to cause ozone cracking under stress.
(6) rubber products: in the process of use, if long-term contact with the oil medium, the oil can penetrate into the rubber and cause it to swell, resulting in the reduction of the strength and other mechanical properties of the rubber. Oil can cause rubber swelling, because the oil into rubber, the production of molecular diffusion, so that the network structure of vulcanized rubber changes. Other factors: chemical media, valence metal ions, high energy radiation, electricity and biology.
(7) moisture: there are two functions of moisture: rubber is easy to be destroyed in wet air or soaked in water, which is caused by water extraction, dissolution, hydrolysis or absorption of water-soluble substances and hydrophilic groups in rubber. Especially in the alternate action of water immersion and atmospheric exposure, will accelerate the destruction of rubber. However, in some cases, the water on the rubber is not destructive effect, and even delay the aging effect.