Ante imported solid silicone o-rings, steam resistant silicone o-ring permanent deformation: As the imported materials resistant synthetic rubber o-rings with water vapor is part of a viscoelastic material, the initial setting of the compression and rebound amount by plugging capability prolonged use, will produce permanent deformation gradually lose eventually leak. Permanent deformation and elasticity are the main reason for the disappearance of imported silicone o-ring sealing properties are lost, the following are the main reason for causing permanent deformation. 1) the relationship between compression ratio and the amount of stretching permanent modification 2) the relationship between temperature and imported silicone o-rings Relaxation processes 3) media work stress and permanent deformation distort injury: cause reason of imports resistance to steam o-ring twisted Injury lot , the most important is due to clearance between the piston rod and the cylinder is uneven, eccentric too large, O-ring cross section diameter caused by uneven, due to the friction caused by uneven imported silicone O-ring in more than a week by the Some parts of the friction o-ring is too big, distorted. Typically, cross-sectional dimensions smaller O-ring, prone to friction uneven. Distorting (sports with O-ring cross section diameter than the fixing O-ring big is the truth.) In addition, since the sealing groove there concentricity error, seal height is not equal and import resistance to steam o-ring sectional diameter not even other phenomena, may make part of O-ring compression is too large, the other part is too small or not compressed. When the presence of the eccentric groove that is concentric deviation is greater than the amount of water vapor resistance to compression of imports o-ring seal will be completely ineffective. Import compression silicone o-ring materials permanent deformation rate and temperature. When the variation rate of 40% or more, that there will be leaks, so some rubber heat resistance limit of: NBR 70 ℃, EPDM 100 ℃, fluorine rubber 140 ℃. Therefore States O-ring makes provision for permanent deformation. Chinese standard rubber O-ring material at different temperatures of dimensional change table. O-rings of the same material at the same temperature, the cross-sectional diameter of importing silicone o-ring compression rate lower permanent deformation. In the oil situation is different. Since this time O-ring is not in contact with oxygen, as occurs in dynamic sealing state. If the O-ring fitted properly, and appropriate conditions of use, are generally less prone to rolling, or distorted in a reciprocating motion, because the area of ??contact with the O-ring groove is greater than the frictional contact area on the sliding surface, and an O- Circle's own ability to resist distortion of the original will be able to stop. Distribution of friction tends to keep O-ring is stationary in its groove, because static friction is greater than sliding friction, and import silicone o-ring groove surface roughness is generally not as good as the sliding surface roughness.