Oil seal is the customary name of general seals, which is simply the seal of lubricating oil. It is used to seal grease (oil is a common liquid substance in the transmission system, also refers to the general meaning of liquid substances) mechanical components, it will drive parts in need of lubrication and output parts of isolation, so as not to let lubricant leakage. Static and dynamic seals (general reciprocating motion) are called oil seals with seals. The representative form of oil seal is TC oil seal, which is a double lip oil seal with self-tightening spring completely covered by rubber. Generally speaking, oil seal often refers to this TC skeleton oil seal.
Common materials for oil seals are: Nitrile rubber (NBR), fluorine rubber(FKM), silicone rubber, acrylic rubber, polyurethane, polytetrafluoroethylene and so on.
It has good heat resistance, wear resistance, resistance to various lubricants, greases, oil and gas mixtures, suitable for temperature - 30 - 120 degrees Celsius, but can no longer be used in phosphate hydraulic oil and gear oil containing extreme pressure additives, stable performance in gasoline and mineral oil with low aniline point.
2. Polyacrylate rubber (ACM)
Excellent oil and heat resistance, abrasion resistance, ozone resistance, ultraviolet radiation resistance, especially extreme pressure fluid containing lubricants, gear oil, motor oil, oil series hydraulic oil, etc., suitable for - 30 - 150 degrees Celsius range of work.
3. Fluororubber (FPM)
Aging resistance, heat resistance, oil resistance, almost applicable to all lubricants, fuel oils, gasoline, oil containing extreme pressure additives is not easy to harden, but cold resistance, high temperature wear resistance is poor, compression deformation is large, suitable for temperature - 20 ~ 250 degrees Celsius.
4. silicone rubber
It has outstanding resistance to high and low temperatures, can be used at 150 degrees Celsius for a long time without performance change, can be used at 200 degrees Celsius for 10,000 hours continuously, and can maintain its unique use flexibility, ozone resistance and weather resistance in the operating temperature range of - 70-260.
It has outstanding chemical stability, thermal stability, friction reduction and self-lubrication. Its pyrolysis temperature is over 400. Therefore, it can work normally in the temperature range of - 200 - 300 degrees Celsius. Except for free fluorine and alkali metals, it has excellent corrosion resistance to chemicals, solvents, hydroxides and acids.
Nitrile butadiene rubber (NBR) and fluorine rubber (FBR) are widely used oil seals. The former has low cost, but its temperature resistance and sealing performance have been improved obviously, but the cost is higher, and it still has some bad common characteristics of ordinary rubber materials, such as poor wear resistance, short service life, especially sensitive to the eccentricity of the shaft, etc. Leakage phenomenon is still widespread. PTFE oil seal is a product with high technology content, which is the direction of oil seal development in the future.
When choosing the material of oil seal, the compatibility of material to working medium, the adaptability to working temperature range and the ability of lip edge to follow the rotating axis at high speed must be considered. Generally, the temperature of lip edge is higher than that of working medium at 20-50 C. Attention should be paid to the selection of oil seal materials. The working range of oil seals is related to the materials used in oil seals: NBR, ACM, FPM and NBR.