Since synthetic rubber O-ring material used belongs to a viscoelastic material, the amount of pressing and rebound blocked the ability of the initial setting after a long period of use, it will produce permanent deformation gradually lose eventually leak. Permanent deformation and elastic disappear is the main reason for the loss of O-ring sealing performance.

　　Shenzhen silicone products plant - Levin Xin die specializing in O-ring production, development for 10 years, now share with you cause permanent deformation of the O-ring mainly has the following three aspects:

1, temperature O-ring permanent deformation

Use Temperature is another important factor in the O-ring of permanent deformation. High temperature will accelerate the aging of the rubber material. The higher the temperature, the compression set O-ring will be. When the permanent deformation is greater than 40%, O-ring seal will lose the ability to leak. The initial stress due to compressive deformation of the O-ring of rubber material formed with the O-ring of the relaxation process and the role of temperature decrease gradually reduced so as to disappear. Working temperature of minus O-ring, which may be due to initial compression temperature decreases drastically reduced or disappear completely. In the case of -50 ~ -60 ℃, low-temperature resistance of the rubber material will completely lose the initial stress; low temperature even if the rubber material, the initial stress at this time is not more than 25% 20 ℃ initial stress. This is because the initial amount of compression depends on the O-ring coefficient of linear expansion. Therefore, the selection of initial compression, we must ensure due process and the relaxation of stress caused by temperature drop after drop still sufficient sealing capacity.

　　Working temperature of minus O-ring, special attention should be recovery index and index of deformation of rubber materials.

In summary, silicone products factory in Shenzhen - Levin Xin mold that: the design should try to ensure that the O-ring having a suitable operating temperature, or use high resistance, low temperature O-ring material, in order to extend the service life.

2, compression and tensile rate on permanent deformation

　　Production of formulations used in the O-ring rubber, in a compressed state will have a compression stress relaxation phenomenon, this time, the compressive stress decreases the growth over time. Use longer, the greater the compression ratio and the amount of stretch, by rubber stress relaxation and stress generated greater decline, resulting in lack of O-ring elasticity, loss of sealing ability. Therefore, under the allowed conditions of use, trying to reduce the compression ratio is desirable. Increased cross-sectional dimensions of the O-ring is to reduce the compression ratio of the easiest way, but it will bring increased structure size.

It should be noted that people in the calculation of the compression ratio, often overlooked section height reduced O-ring in the assembly caused by stretching. Changes O-ring cross-sectional area is inversely proportional to the change and its perimeter. At the same time, due to the tension of the cross-sectional shape of the O-ring will change, on the performance of its height reduced. In addition, the surface tension of the outer surface of the O-ring becomes more flat, and that section height decreases slightly. It is also a manifestation of the O-ring compression stress relaxation.

Section deformation degree of the O-ring, but also on the O-ring material hardness. In the case of the same amount of stretch, large hardness O-ring cross section height is reduced more, from this point of view, we should be in accordance with the conditions of use try to use low hardness material. Under the influence of fluid pressure and tension of the rubber O-ring material will gradually plastically deformed, its section height will be reduced accordingly, so that the final loss of sealing ability.

　　3, the working medium pressure causes permanent deformation of the O-ring

Pressure of the working medium is a major factor causing the O-ring of permanent deformation. Working pressures of modern hydraulic equipment are increasing. Long high pressure causes the O-ring permanent deformation. Therefore, the design should be the choice of appropriate pressure rubber material according to the working pressure. The higher operating pressure, high pressure and hardness properties of the materials used should also be higher.

In order to improve the withstand voltage characteristics of the O-ring material, increase the flexibility of the material (in particular increased low temperature flexibility of the material, to reduce the compression permanent deformation of the material, the need to improve the general formula of the material, a plasticizer is added. However, with the enhanced O-ring sealed plastic agent, long soak in the working medium, the plasticizer will gradually be absorbed by the working medium, resulting in volume contraction O-ring, the O-ring may even produce negative compression (ie O-sealed in gaps between the seal ring and the surface). Thus, in calculating the amount of compression and O-ring mold design, should be fully taken into account the amount of shrinkage. should be pressed out of the O-ring in the working medium still maintain the necessary size soak 5 to 10 days and nights.

Compression set temperature-dependent O-ring material. When the deformation rate of 40% or more, that there will be leaks, so some rubber heat resistance limit of: NBR 70 ℃, EPDM 100 ℃, Viton 140 ℃. Therefore States permanent deformation O-rings made provisions. Chinese standard rubber O-ring material change in the size table at different temperatures. O-ring of the same material, at the same temperature, a large cross-sectional diameter of the O-ring compression rate is low permanent deformation.

　　In the oil situation is different. Since this time the O-ring is not in contact with oxygen, so these adverse reactions is greatly reduced. Coupled compound and usually causes a certain degree of expansion, so the compression set caused by temperature will be canceled. Therefore, in the oil heat greatly improved. In nitrile rubber, for example, its operating temperature up to 120 ℃ or higher.

Since synthetic rubber O-ring material used belongs to a viscoelastic material, the amount of pressing and rebound blocked the ability of the initial setting after a long period of use, it will produce permanent deformation gradually lose eventually leak. Permanent deformation and elastic disappear is the main reason for the loss of O-ring sealing performance.

　　Shenzhen silicone products plant - Levin Xin die specializing in O-ring production, development for 10 years, now share with you cause permanent deformation of the O-ring mainly has the following three aspects:

1, temperature O-ring permanent deformation

Use Temperature is another important factor in the O-ring of permanent deformation. High temperature will accelerate the aging of the rubber material. The higher the temperature, the compression set O-ring will be. When the permanent deformation is greater than 40%, O-ring seal will lose the ability to leak. The initial stress due to compressive deformation of the O-ring of rubber material formed with the O-ring of the relaxation process and the role of temperature decrease gradually reduced so as to disappear. Working temperature of minus O-ring, which may be due to initial compression temperature decreases drastically reduced or disappear completely. In the case of -50 ~ -60 ℃, low-temperature resistance of the rubber material will completely lose the initial stress; low temperature even if the rubber material, the initial stress at this time is not more than 25% 20 ℃ initial stress. This is because the initial amount of compression depends on the O-ring coefficient of linear expansion. Therefore, the selection of initial compression, we must ensure due process and the relaxation of stress caused by temperature drop after drop still sufficient sealing capacity.

　　Working temperature of minus O-ring, special attention should be recovery index and index of deformation of rubber materials.

In summary, silicone products factory in Shenzhen - Levin Xin mold that: the design should try to ensure that the O-ring having a suitable operating temperature, or use high resistance, low temperature O-ring material, in order to extend the service life.

2, compression and tensile rate on permanent deformation

　　Production of formulations used in the O-ring rubber, in a compressed state will have a compression stress relaxation phenomenon, this time, the compressive stress decreases the growth over time. Use longer, the greater the compression ratio and the amount of stretch, by rubber stress relaxation and stress generated greater decline, resulting in lack of O-ring elasticity, loss of sealing ability. Therefore, under the allowed conditions of use, trying to reduce the compression ratio is desirable. Increased cross-sectional dimensions of the O-ring is to reduce the compression ratio of the easiest way, but it will bring increased structure size.

It should be noted that people in the calculation of the compression ratio, often overlooked section height reduced O-ring in the assembly caused by stretching. Changes O-ring cross-sectional area is inversely proportional to the change and its perimeter. At the same time, due to the tension of the cross-sectional shape of the O-ring will change, on the performance of its height reduced. In addition, the surface tension of the outer surface of the O-ring becomes more flat, and that section height decreases slightly. It is also a manifestation of the O-ring compression stress relaxation.

　　Section deformation degree of the O-ring, but also on the O-ring material hardness. In the case of the same amount of stretch, large hardness O-ring cross section height is reduced more, from this point of view, we should be in accordance with the conditions of use try to use low hardness material. Under the influence of fluid pressure and tension of the rubber O-ring material will gradually plastically deformed, its section height will be reduced accordingly, so that the final loss of sealing ability.

　　3, the working medium pressure causes permanent deformation of the O-ring

Pressure of the working medium is a major factor causing the O-ring of permanent deformation. Working pressures of modern hydraulic equipment are increasing. Long high pressure causes the O-ring permanent deformation. Therefore, the design should be the choice of appropriate pressure rubber material according to the working pressure. The higher operating pressure, high pressure and hardness properties of the materials used should also be higher.

In order to improve the withstand voltage characteristics of the O-ring material, increase the flexibility of the material (in particular increased low temperature flexibility of the material, to reduce the compression permanent deformation of the material, the need to improve the general formula of the material, a plasticizer is added. However, with the enhanced O-ring sealed plastic agent, long soak in the working medium, the plasticizer will gradually be absorbed by the working medium, resulting in volume contraction O-ring, the O-ring may even produce negative compression (ie O-sealed in gaps between the seal ring and the surface). Thus, in calculating the amount of compression and O-ring mold design, should be fully taken into account the amount of shrinkage. should be pressed out of the O-ring in the working medium still maintain the necessary size soak 5 to 10 days and nights.

　　Compression set temperature-dependent O-ring material. When the deformation rate of 40% or more, that there will be leaks, so some rubber heat resistance limit of: NBR 70 ℃, EPDM 100 ℃, Viton 140 ℃. Therefore States permanent deformation O-rings made provisions. Chinese standard rubber O-ring material change in the size table at different temperatures. O-ring of the same material, at the same temperature, a large cross-sectional diameter of the O-ring compression rate is low permanent deformation.

　　In the oil situation is different. Since this time the O-ring is not in contact with oxygen, so these adverse reactions is greatly reduced. Coupled compound and usually causes a certain degree of expansion, so the compression set caused by temperature will be canceled. Therefore, in the oil heat greatly improved. In nitrile rubber, for example, its operating temperature up to 120 ℃ or higher.