1、 Tensile properties
Tensile property is the first property to be considered for rubber seals, which includes tensile strength, constant tensile stress, elongation at break, deformation at break, etc. The tensile strength is the large stress from tensile to fracture of the material sample; The constant elongation stress is the stress reached at the specified elongation; Elongation is the deformation (ratio of elongation increment to original length) caused by the specified tensile force on the material sample, and elongation at break is the elongation at break of the sample; The tensile deformation is the residual deformation between the markings after tensile fracture of materials.
Hardness refers to the ability of rubber seals to resist external force and is one of the basic properties of seals. The hardness of rubber seals is also closely related to other properties. For example, the higher the hardness of rubber seals, the greater the strength, the smaller the elongation, and the better the wear resistance, while the low temperature resistance is often inversely proportional to the hardness.
3、 Compression performance
Rubber seals are usually compressed. The rubber material has viscoelasticity, and the pressure will decrease with time when it is compressed, showing the relaxation of compression stress; After removing the pressure, it can not return to the original shape, which is shown as compression deformation. This phenomenon is more obvious in high temperature and oil medium, and this performance is directly related to the durability of rubber sealing capacity.
4、 Aging resistance
When rubber seals are subjected to oxygen, cold and hot, moisture, mechanical stress, etc., their performance will deteriorate, which is called aging. The aging resistance can be expressed by the change of strength, elongation and hardness of rubber seals after aging. The smaller the change rate is, the better the aging resistance is.
5、 Oil or medium resistance
In the application of vacuum system, rubber seals are exposed to many mediums, such as petroleum based, diester, silicone grease oil, and acid, alkali and other corrosive mediums in the chemical industry. In these media, the rubber seal is not only corroded, but also can cause expansion, strength and hardness reduction under high temperature. At the same time, the plasticizer and soluble substances in the rubber seals are extracted, which will lead to the reduction of mass and volume, thus leading to the leakage of the vacuum system. Generally, under a certain temperature, the quality, volume, strength, elongation, hardness and other property changes of rubber seals are measured after immersion in the medium for a certain period of time to evaluate the oil resistance or medium resistance of rubber seals.
6、 Low temperature performance
The low-temperature performance of rubber seals has two aspects:
①Low temperature retraction temperature. Stretch the seal to a certain length, then fix it, quickly cool it to below the freezing temperature, loosen it after reaching balance, and raise the temperature at a certain speed. Record the temperature when the material shrinks 10%, 30%, 50% and 70%, expressed as TR10, TR30, TR50 and TR70 respectively. The material standard is TR10, which is related to the brittleness temperature of rubber.
② Low temperature flexibility. After the material is frozen at a certain low temperature for a specified time, it is bent back and forth at a specified angle. At this time, the sealing ability of rubber seals under the repeated action of dynamic load at low temperature is investigated.
Through the comparison of the above six aspects, we can basically get the performance advantages and disadvantages of the same type of rubber seals between different manufacturers. After comprehensive comparison, we choose the best.
Post time: Sep-21-2022