Several important factors for choosing O-rings! When ch […]
Several important factors for choosing O-rings!
When choosing a seal, we must first consider its tensile strength, tensile stress, elongation, elongation at break, permanent deformation at break, and stress-strain curve. These are collectively referred to as tensile strength. The so-called tensile strength is actually the maximum tensile stress when the sample is stretched to break. The constant elongation stress is the stress reached at the specified elongation. The elongation is the deformation of the sample caused by the tensile stress, expressed as a percentage of the ratio of the increase in elongation to the original length. The elongation at break is the elongation when the sample is broken.
In addition, we also need to consider the basic properties of stamp hardness. Hardness is the ability of rubber to resist external pressure. The hardness of rubber is partly related to other properties. For example, rubber has high hardness, high strength, low elongation, good wear resistance, and poor low temperature resistance. High-hardness rubber can resist compression and damage under high pressure. Therefore, the appropriate hardness should be selected according to the working characteristics of the part.
We all know that rubber seals are usually in compression, so in addition to these, we also need to consider the compression performance of the seal. Due to the viscoelasticity of rubber, the compressive stress decreases with time after compression, and the compressive stress relaxes. After the pressure is removed, the original shape cannot be restored, and the expression is compression permanent deformation. These phenomena are more obvious in high temperature and oily media. They can affect the sealing performance, and can also affect the important performance of the sealant. ---O-ring
As we all know, the choice of O-ring material is of great significance to its sealing performance and service life. The performance of the material directly affects the performance of the O-ring. In addition to the general requirements for sealing ring materials, O-rings should also pay attention to the following conditions:
(1) Full of flexibility and resilience;
(2) Appropriate mechanical strength, including expansion strength, elongation and tear resistance.
(3) The performance is stable, it is not easy to swell in the medium, and the thermal contraction effect (Joule effect) is small.
(4) It is easy to process and shape, and can maintain precise dimensions. To
(5) Does not corrode the contact surface, does not pollute the medium, etc. To
The most suitable and commonly used material to meet the above requirements is rubber, so most O-rings are made of rubber. There are many types of rubber, and new types of rubber are constantly appearing. When designing and selecting, one should understand the characteristics of various rubbers and choose them reasonably.