Piston Rod Seal PU

We believe that the performance of seals depends on the following aspects:

strength. The strength of the material determines how much pressure the Seal can withstand. Polyurethane has high tensile strength, and polyurethane seals can withstand greater pressure than rubber seals. We believe that at smaller deformations, the greater the 100% modulus of the material, the more stress the seal is subjected to.
Resilience. The seal must have excellent resilience properties with low tensile deformation.

Compression set. This is the most important performance indicator for seals. In the static state, the seal is squeezed for a long time; in the working state, the seal is in the process of pressure and release cycle, no matter what the situation is, after the pressure is removed, the seal is required to quickly return to its original size. At the same time, in the working state, it is generally in a high temperature environment, so the Sealing material must have extremely low compression set at room temperature and high temperature.

Media resistance. First of all, there is a small amount of moisture in the hydraulic oil. If the hydrolysis resistance of the polyurethane does not meet the requirements, as the use time increases, the seal will be cracked due to the hydrolysis of the material, loss of strength, wear, stickiness and other phenomena, thus losing the seal. Secondly, it can resist the erosion of hydraulic oil, that is, the swelling rate is as low as possible, otherwise the seal will swell and become fat, resulting in a decrease in tensile strength, especially the 100% modulus, and we found that the old hydraulic oil has a negative effect on the seal. The swelling effect is much greater than that of new hydraulic oil, and the swelling rate is about 3 to 5 times higher, so new oil should be used as much as possible if possible; there are also some special occasions where emulsion liquid is used instead of hydraulic oil, in which case seals must be considered The medium resistance of the material is the first choice.

 Heat resistance. Frequent reciprocating motion and friction will generate heat, so it is required that the hardness, 100% modulus, especially the compression set and other properties of the seal should not be lost too much in the high temperature hydraulic oil for a long time.

 Fatigue resistant. That is, good dynamic performance. The fatigue resistance of Polyurethane Sealing Ring must be considered when it is used in some occasions with high working frequency. Otherwise, stress relaxation will occur and lead to deformation of the Sealing ring, thereby reducing the sealing performance, such as nitrogen gas springs, breakers, etc.

 Wear resistance. Although there is hydraulic oil as the lubricating medium, friction will still occur during the relative movement, especially the high pressure forces the lip to be close to the piston rod or inner wall, causing the lip to wear; at the same time, impurities in the hydraulic oil are also lip wear. One of the factors, so the polyurethane must have excellent wear resistance and low friction coefficient. The use of special lubricants can reduce the coefficient of friction of polyurethane and reduce frictional heat, especially in cylinder applications.

Low temperature resistance. Seals may be sent to high-cold areas at home and abroad along with supporting equipment. At this time, the low temperature resistance of the material is very important. The low temperature resistance range of ordinary polyurethane materials is -20 ~ -35 °C, but in alpine regions, it needs to withstand low temperatures of -40 or even -50 °C, so low temperature resistance is a very important indicator.