What are the reasons for rubber aging?
Rubber is the raw material of many products, and rubber is not immutable. With the environmental conditions and time factors, rubber will age and lose its original characteristics. What are the reasons for rubber aging?
What is rubber aging? In the process of processing, storage and use of rubber and its products, due to the comprehensive effect of internal and external factors, the physical and chemical properties and mechanical properties of rubber gradually deteriorate, and finally lose the use value. This change is called rubber aging. Rubber aging performance is cracking, sticky, hardening, softening, powdering, discoloration, mildew and so on.
The aging factors of rubber are as follows:
A) Oxygen: the free radical chain reaction between oxygen and rubber molecules occurs in rubber, the molecular chain is broken or over crosslinked, which causes the change of 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, which is 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 the rubber is used for deformation (mainly unsaturated rubber), there are cracks which are straight with the direction of stress action, that is the so-called "ozone cracking"; when the rubber is used for deformation, only oxide film is formed on the surface without cracking.
C) Heat: increase of 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 can accelerate rubber oxidation reaction rate, which is a common aging phenomenon thermal oxygen aging.
D) Light: the shorter the light wave, the greater the energy. The destruction of rubber is caused by ultraviolet rays with high energy. In addition to the breaking and crosslinking of rubber molecular chain directly caused by ultraviolet radiation, the rubber can absorb light energy and produce free radicals, which initiate and accelerate the oxidation chain reaction process. The outside ray plays a role of heating. Another characteristic of light action (different from heat action) is that it mainly grows on the surface of oak. For samples with high gel content, network cracks will appear on both sides, which is called "light outer layer crack".
E) Mechanical stress: under the repeated action of mechanical stress, the rubber molecular chain will break and generate free radicals, which will trigger oxidation chain reaction and form a mechanochemical process. The molecular chain is broken and the oxidation process is activated. Which one can be dominant depends on the conditions. In addition, it is easy to cause ozone cracking under stress.
F) Moisture: there are two functions of moisture: rubber is easy to be damaged when it is soaked in water or wet air, which is caused by the water-soluble substances and hydrophilic groups in rubber are extracted, dissolved, hydrolyzed or absorbed by water. Especially under the alternate action of water immersion and atmospheric exposure, the damage of rubber will be accelerated. However, in some cases, moisture does not damage the rubber, and even has the effect of delaying aging.
G) Oil: in the process of use, if it has long-term contact with the oil medium, the oil can penetrate into the rubber and cause swelling, resulting in the decrease of the strength and other mechanical properties of the rubber. Oil can make rubber swelling, because the oil into the rubber, resulting in the molecular diffusion, so that the network structure of vulcanizate changes.
H) Other factors: chemical medium, variable valence metal ions, high energy radiation, electricity, biology and so on.
Therefore, the products provided by gmtlight, which are made of rubber raw materials, have their own life. After the expiration date, they will enter the recycle bin.