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How the viscoelasticity of the silicone seal ring is composed
Release time:
2021-06-29 11:12
Source:
Dongguan Mingzhen
The initial contraction of the O-ring seal operating at minus temperature may be reduced or completely disappeared due to the sharp drop in temperature. Under the condition of -50 ~-60 ℃, the rubber material that is not resistant to low temperature will completely lose the initial stress. Even for the rubber material that is resistant to low temperature, the initial stress at this moment will not be greater than 25% of the initial stress at 20 ℃, because the initial contraction of the silicone seal ring depends on the linear expansion coefficient.

The pressure of the working medium is the main factor causing the deformation of the silicone sealing ring. The working pressure of modern hydraulic equipment is increasing day by day. The long-term high-pressure action of the sealing ring will deform the silicone sealing ring. Therefore, the design should be based on the working pressure. Appropriate pressure-resistant rubber materials, the higher the working pressure, the higher the hardness and high pressure resistance of the materials used.
In order to improve the pressure resistance of the silicone sealing ring material and increase the elasticity of the material (especially to increase the elasticity of the material at low temperature and reduce the compression deformation of the material, it is generally necessary to improve the formula of the material and add plasticizer. However, if the silicone sealing ring with plasticizer is soaked in the working medium for a long time, the plasticizer will be gradually absorbed by the working medium, resulting in the volume shrinkage of the silicone sealing ring, it is even possible to cause negative compression of the silicone seal ring (I. e., a gap between the silicone seal ring and the surface to be sealed).
Because the rubber material used in the silicone sealing ring belongs to the viscoelastic material, the compression amount and rebound blockage set in the initial stage can be used for a long time, resulting in permanent deformation and gradual loss, leakage, permanent deformation and elastic force disappearance are the main reasons for the loss of sealing function of the O-ring.
Operating temperature is another important factor affecting the permanent deformation of silicone sealing ring. High temperature will accelerate the aging of rubber materials. The higher the operating temperature, the greater the permanent deformation of silicone sealing ring. When the permanent deformation is greater than 40%, the O-ring will lose its sealing ability and leak. The initial stress value formed in the rubber materials of silicone sealing ring due to contraction deformation, it will gradually decrease and disappear with the relaxation process of silicone sealing ring pressed by silicone keys and the effect of temperature drop.
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