The synthetic rubber material used in the silicone sealing ring belongs to viscoelastic material. Therefore, if long-term use of clamping and rebound blocking ability, deformation, gradually lose elasticity, resulting in leakage, loss of sealing performance.
1. medium pressure
The working pressure of modern hydraulic machinery is increasing. Long-term high pressure will make the silicone sealing ring deformation, lose the sealing performance. Therefore, appropriate compressive plastic materials should be used in the design according to the working pressure. The greater the working pressure, the greater the hardness and high pressure resistance of the material used. Generally speaking, in order to improve the compressive performance of silicone sealing rings and the elasticity of materials, it is necessary to improve the formula of materials and add viscosifier. However, if the adhesive is added to the silicone sealing ring, soak in the medium for a long time, the adhesive will be slowly absorbed by the medium, leading to the volume contraction of the silicone sealing ring, may also lead to the negative compression of the silicone sealing ring.
Therefore, when calculating the compression amount of silicone sealing ring and designing the mold, these shrinkage amounts should be fully considered. After soaking in the medium for 5 to 10 days, the suppressed silicone seal can still maintain the necessary size.
2.temperature
High temperature will accelerate the aging of plastic materials. The higher the operating temperature, the greater the long-term compression deformation of the silicone seal ring. When the long-term deformation exceeds 40%, the sealing ring will lose its sealing performance, leading to leakage. As the tension process and temperature decrease, the initial stress value formed by the compression deformation of the seal ring will gradually decrease, leading to extinction. O-type silicone seals work at below zero, and initial compression may be reduced or completely lost due to a sharp drop in temperature. At -50~60℃, plastic materials that are not resistant to low temperature will completely lose their initial stress. Because the initial compression of the silicone sealing ring depends on the coefficient of expansion.
3. compression rate and tensile amount
The various rubber formulations used to make silicone seals will produce compressive stress relaxation under compression conditions, and the compressive stress will decrease over time. The longer the use time, the greater the compression rate and tensile amount, the greater the stress reduction caused by rubber stress relaxation, resulting in insufficient elasticity of the O-type silicone sealing ring, the loss of sealing ability.
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