Seal performance and material application
In addition to the general requirements for the material of the seal ring, the main performance of the seal ring should also pay attention to the following conditions:
(1) Flexibility and resilience;
(2) Appropriate mechanical strength, including expansion strength, elongation and tear strength.
(3) The performance is stable, it is not easy to swell in the medium, and the heat shrinkage effect (Joule effect) is small.
(4) Easy to process and maintain precise dimensions.
(5) Does not corrode the contact surface, does not contaminate the medium, etc.
The most suitable and most commonly used material to meet the above requirements is rubber, so the seals are mostly made of rubber. There are many varieties of rubber, and there are new varieties of rubber. When designing and selecting, you should understand the characteristics of various rubbers and make reasonable choices.
1. NBR nitrile rubber sealing ring: It is suitable for use in petroleum-based hydraulic oil, glycol-based hydraulic oil, diester-based lubricating oil, gasoline, water, silicon grease, silicone oil and other media. It is currently the most versatile and lowest cost rubber seal. Not suitable for use in polar solvents such as ketones, ozone, nitrohydrocarbons, MEK and chloroform. The general temperature range is -40~120 °C.
Second, HNBR hydrogenated nitrile rubber sealing ring: It has excellent corrosion resistance, tear resistance and compression deformation resistance, and is resistant to ozone, sunlight and weather. Better wear resistance than nitrile rubber. Suitable for use in washing machines, automotive engine systems and refrigeration systems using the new environmentally friendly refrigerant R134a. Not recommended for use in alcohols, esters or aromatic solutions. The general temperature range is -40~150 °C.
Third, SIL silicone rubber sealing ring: It has excellent heat resistance, cold resistance, ozone resistance and atmospheric aging resistance. Has good insulation properties. However, the tensile strength is inferior to that of ordinary rubber and does not have oil resistance. Suitable for household appliances such as electric water heaters, electric irons, microwave ovens, etc. It is also suitable for all kinds of articles that come into contact with the human body, such as water bottles and water dispensers. Not recommended for use in most concentrated solvents, oils, concentrated acids and sodium hydroxide. The general temperature range is -55~250 °C.
IV. VITON Fluorine Rubber Seal: High temperature resistance is superior to silicone rubber. It has excellent weather resistance, ozone resistance and chemical resistance, and poor cold resistance. It is resistant to most oils and solvents, especially acids, aliphatic hydrocarbons, aromatic hydrocarbons and animal and vegetable oils. Suitable for sealing requirements in diesel engines, fuel systems and chemical plants. It is not recommended for use in ketones, low molecular weight esters and mixtures containing nitrates. The general temperature range is -20~250 °C.
V. FLS fluorosilicone rubber sealing ring: Its performance has the advantages of fluorocarbon rubber and silicone rubber, and it is good in oil resistance, solvent resistance, fuel oil resistance and high and low temperature resistance. It is resistant to attack by oxygen-containing compounds, aromatic-containing solvents, and chlorine-containing solvents. Generally used in aviation, aerospace and military applications. Exposure to ketones and brake fluids is not recommended. The general temperature range is -50~200 °C.
6. EPDM EPDM rubber seal: It has good weather resistance, ozone resistance, water resistance and chemical resistance. It can be used in alcohols and ketones, and it can also be used for sealing in high temperature water vapor environment. Suitable for use in sanitary equipment, automotive radiators and automotive brake systems. Not recommended for food use or exposure to mineral oil. The general temperature range is -55~150 °C.
Seven, CR neoprene seal: Sunshine, weather resistance performance is particularly good. It is not afraid of refrigerants such as dichlorodifluoromethane and ammonia. It is resistant to dilute acid and silicone grease, but it has a large amount of expansion in mineral oil with low aniline point. It is easy to crystallize and harden at low temperatures. Applicable to all kinds of environments exposed to the atmosphere, sunlight, ozone and various flame-resistant and chemical-resistant sealing parts. It is not recommended for use in chemicals such as strong acids, nitrohydrocarbons, esters, chloroforms and ketones. The general temperature range is -55~120 °C.
Eight, IIR butyl rubber sealing ring: air tightness is particularly good, heat resistance, sunlight resistance, ozone resistance, good insulation performance; good resistance to polar solvents such as alcohols, ketones, esters, etc., can be exposed In animal and vegetable oils or in oxides. Suitable for chemical resistant or vacuum equipment. It is not recommended for use with petroleum solvents, kerosene or aromatics. The general temperature range is -50~110 °C.
Nine, ACM acrylate rubber seal: Excellent resistance to oil, high temperature and weather resistance, but mechanical strength, compression deformation and water resistance are slightly worse. Generally used in automotive transmission systems and power steering systems. Not suitable for use in hot water, brake fluid, and phosphate esters. Typical operating temperatures range from -25 to 170 °C.
Ten, NR natural rubber seal: has good wear resistance, elasticity, tear strength and elongation. However, it is easy to age in the air, becomes sticky when exposed to heat, easily swells and dissolves in mineral oil or gasoline, and is alkali-resistant but not resistant to strong acid. It is suitable for use in liquids such as automobile brake oil and ethanol with hydroxide ions. The general temperature range is -20~100 °C.
XI. PU polyurethane rubber sealing ring: The mechanical properties of polyurethane rubber are very good, and the wear resistance and high pressure resistance are far superior to other rubbers. Aging resistance, ozone resistance, and oil resistance are also quite good, but high temperature is easily hydrolyzed. Generally used for high pressure and wear resistant sealing parts, such as hydraulic cylinders. The general temperature range is -45~90 °C.
Twelve, metal rubber sealing ring: made of stainless steel wire, does not contain any rubber components, has strong use characteristics. For example: keep working under high vacuum, high and low temperature, strong radiation, and various corrosive environments. The skin of the sealing ring is made of different materials such as stainless steel, copper, PTFE, etc. according to the application. The coated metal rubber member is used as the core, which has the advantages of high sealing strength, good effect and reusability. The seal core is made of different wire diameters and densities and is suitable for different pressure applications. The general use range is -80~800 °C. Such a seal is expensive because of its high cost. However, good performance and a wide range of use environments have been recognized by people.