Raw rubber or rubber products in the process of processing, storage or use, will be affected by heat, oxygen, light and other clean factors and gradually undergo physical and chemical changes, so that its performance is reduced, and the loss of use, this phenomenon is called rubber aging.

The aging process of rubber is often accompanied by some significant phenomena, such as the appearance of long-term storage of natural rubber can be found soft, sticky, spots; Rubber products have deformation, brittleness, hardness, cracking, mildew, loss of light and color change. In physical properties, rubber has swelling, rheological properties and other changes. In mechanical properties, tensile strength, elongation at break, impact strength, bending strength, compression, elasticity and other indicators will decrease.

1. Oxygen

Oxygen in rubber and rubber molecules have free group chain reaction, molecular chain fracture or excessive crosslinking, resulting in rubber properties change. Oxidation is one of the important reasons for rubber aging.

2. Ozone

The chemical activity of ozone is much higher than oxygen, more destructive, it is the same to break the molecular chain, but the effect of ozone on rubber varies with the deformation of rubber. When used as a rubber for deformation (mainly unsaturated rubber), there is a crack perpendicular to the direction of stress action, that is, the so-called "ozone cracking"; When acting on the deformed rubber, only the surface of the oxide film is formed without cracking.

3. Heat

Increasing the temperature can cause thermal cracking or thermal crosslinking of rubber. But the basic function of heat is activation. Increasing the oxygen diffusion rate and activation oxidation reaction, thereby accelerating the rubber oxidation reaction rate, which is a universal aging phenomenon - hot oxygen aging.

4. Light

The shorter the light wave, the more energy it has. The damaging effect on rubber is the high energy ultraviolet light. In addition to directly causing the break and crosslinking of rubber molecular chains, ultraviolet rays can produce free groups due to the absorption of light energy, triggering and accelerating the oxidation chain reaction process. Ultraviolet light acts as a heating agent. Another characteristic of light action (different from heat action) is that it is mainly produced on the surface of the rubber. The sample with high rubber content will have a network crack on both sides, that is, the so-called "optical outer crack".

5. Mechanical stress

Under the repeated action of mechanical stress, the rubber molecular chain will be broken to form free groups, triggering oxidation chain reaction, forming a mechanochemical process. Mechanical breakage of molecular chains and mechanical activation and oxidation processes. Which will prevail depends on the conditions in which it is situated. In addition, it is easy to cause ozone cracking under the action of stress.

6. Moisture

The role of water has two aspects: When rubber is rained in wet air or soaked in water, it is easy to destroy, which is because the water-soluble substances and water groups in rubber are dissolved by water extraction. Caused by hydrolysis or absorption. Especially under the alternating action of water immersion and atmospheric exposure, the destruction of rubber will be accelerated. However, in some cases, the moisture does not damage the rubber, and even has the effect of delaying aging.

7. Others

The action factors on rubber are also chemical media, variable metal ions, high-energy radiation, electricity and biology.