Rubber and rubber products in the processing, storage and use of the process, due to the comprehensive effect of internal and external factors caused by the physical and chemical properties and mechanical properties of rubber gradually deteriorated, and finally lose value, this kind of change is called aging of rubber. The surface is characterized by crazing, sticking, hardening, softening, powdering, discoloration, mildew and so on. What are the factors that affect the aging of rubber?
Oxygen: oxygen free radical chain reaction in rubber with rubber molecules, the molecular chain rupture or excessive crosslinking caused by rubber performance. Oxidation is one of the important reasons for rubber aging.
Water: the moisture content has two aspects: rubber in the humid air or rain soaked in water, easy to damage, this is because the rubber in water soluble substances and water components by water extraction group Tsuen dissolved. Caused by hydrolysis or absorption. Especially in alternating water immersion and atmospheric exposure, it will accelerate the destruction of rubber. But in some cases, water does not destroy rubber and even retard aging.
Ozone: the chemical reactive oxygen species of ozone is much higher and more destructive, it also breaks the molecular chain, but the effect of ozone on rubber is different with the deformation of rubber. As for the deformation of the rubber (mainly unsaturated rubber), crack and stress direction, the so-called "ozone cracking"; effect on the deformation of the rubber, only surface oxide film without cracking.
Heat: increasing temperature can cause thermal cracking or thermal crosslinking of rubber. But the basic function of heat is activation. Increasing oxygen diffusion rate and activating oxidation reaction, thus accelerating the rate of rubber oxidation reaction, is a widespread aging phenomenon - thermal oxidative aging.
Mechanical stress in mechanical stress under the repeated action, will make the rubber chain fracture generated free Tsuen, causing oxidative chain reaction, the formation of chemical process. Mechanical scission of molecular chains and mechanical activation of oxidation processes. Which is dominant, depending on the conditions in which it is located?. In addition, ozone cracking is easy to be induced under stress.
Light: the shorter the light wave, the greater the energy. Destructive to rubber is ultraviolet radiation with higher energy. In addition to the breaking and crosslinking of rubber molecular chains, the free radicals are produced by the absorption of light energy, and the oxidation chain reaction is accelerated and accelerated. The light acts as an external heating. The other characteristic of light acting on it is different from that of heat. It is mainly produced on the surface of oak. There is a network crack on both sides of the sample with high adhesive ratio, which is called outer layer crack".
Other factors: Rubber and chemical medium, valence metal ion, high-energy radiation, electrical and biological etc..