The aging of rubber seals is usually caused by mechanic […]
The aging of rubber seals is usually caused by mechanical forces, oxidation and ozone oxidation. Generally speaking, aging will make rubber seals embrittlement, accelerate the expansion of fatigue cracks, reduce the critical fracture energy, and reduce its life. The aging process of rubber seals mainly includes the following aspects:
1. Produce mechanical cracking reaction under the action of mechanical force
Due to the viscosity of the polymer, the relaxation process of the rubber in the deformation cycle has not been completed, and the next deformation cycle is entered, which causes the residual stress of the internal deformation of the rubber seal to continue to increase. When the stress gradient is large, it will cause the direct rupture of the rubber molecular chain and the formation of free radicals, which will lead to the oxidation chain reaction and aging of the rubber under the action of oxygen.
2. Mechanical stress will weaken the valence of atoms in the rubber molecular chain, thereby reducing the activation energy of the oxidation reaction. The reduction of oxidative activation energy makes the oxidative cracking of the rubber chain easier and accelerates.
3. The internal heat of the rubber seal accelerates the oxidation reaction
When the rubber seal is repeatedly deformed, it will produce hysteresis, causing internal friction, so that the internal heat of the rubber is generated, and the oxidation chain reaction and aging of the rubber are further accelerated.
4. During the aging process of periodic deformation of rubber seals, ozone cracking occurs, which is more obvious at high temperatures.