1. The role of heat

Increasing the temperature can cause thermal cracking or thermal crosslinking of EPDM products. But the basic function of heat is activation. Increasing the oxygen diffusion rate and activating oxidation reaction, so as to accelerate the rubber oxidation reaction speed, which is a universal aging phenomenon – hot oxygen aging.

2. The role of oxygen

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

3. The cause of light

The shorter the wave, the more energy it has. It is the high energy ultraviolet rays that damage the rubber. Uv can not only directly cause the break and crosslinking of rubber molecular chains, but also generate free groups due to the absorption of light energy, which can trigger and accelerate the oxidation chain reaction process. Ultraviolet light acts as a heating agent. Another characteristic of light action (as opposed to heat action) is that it occurs mainly on rubber surfaces. With high rubber content, both sides of the sample will appear mesh cracks, that is, the so-called “outer light crack”.

4. The role of ozone

Ozone has much higher chemical reactive oxygen species and is more destructive. It also breaks molecular chains, but the effect of ozone on rubber varies with rubber deformation or not. As for the deformation of rubber (mainly unsaturated rubber), and the stress direction of the crack, namely the so-called “ozone cracking”; When acting on the deformed rubber, only the surface of the oxide film without cracking.

5, the role of water

The role of water has two aspects: EPDM rubber products in wet air rain or soak in water, easy to destroy, this is because the water-soluble substances in rubber and water tsuen and other components 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. But in some cases, water on rubber is not destructive, and even has the effect of delaying aging.

6. Other reasons

The aging of EPDM products can also be accelerated by chemical media, variable metal ions, high-energy radiation, electricity and biology.