How to choose oil seal rubber material

 

 

What is an oil seal？

Seals are essential to protecting the bearings of any rotating shaft assembly -They prevent contaminants such as dirt, dust and water, while also preserving the system's lubricant.

 

Choosing the right oil seal material

Oil seals come in many different types and materials depending on their application. Determining the material is vital to ensuring your equipment is operating at its best performance. For example, your equipment may need to run at higher temperature applications, such as an engine seal for a jet engine, you may need to choose a specific material for your oil seals to run properly. In this article, we will explore the most popular and utilized materials in the industry, as well as touch on some of the more unique options out there.

 

 

OIL SEAL MATERIAL

The commonly used materials of oil seal are: nitrile rubber, fluorine rubber,silicone rubber, acrylic rubber, polyurethane, polytetrafluoroethylene and so on. When selecting the material of the oil seal, it is necessary to consider the compatibility of the material to the working medium, the adaptability to the working temperature range and the ability of the lip to follow the rotating shaft when rotating at high speed. Generally, the temperature of the lip edge of the oil seal is 20~50℃ higher than the temperature of the working medium, and attention should be paid to the selection of oil seal materials. The working range of the oil seal is related to the material used in the oil seal: when the material is nitrile rubber (NBR), it is -20~120℃, silicone rubber (Si) is -40~230℃, and Viton (FKM) is -50~300℃.

 

Nitrile

The first material that we are going to look at is Nitrile Buna- N 70 or NBR for short. 

NBR is recommended for the majority of standard applications and is the most commonly used rubber (elastomer) material. This is because of Nitrile's compatibility with most environments as well as its relatively low cost. Generally nitrile is used for disposable non-latex gloves, footwear, automotive transmission belts, synthetic leather, hoses, o-rings, gaskets, oil seals, and more. 

The temperature range of nitrile is −20° to 120 °C. Due to this wide range, NBR seals can be used for gas oil, silicone oil, animal/vegetable oils and fat, hydraulic liquid as well as hot and cold water. In addition, NBR is oil resistant and has an excellent abrasion resistance, so for any application that demands shock absorbers, NBR is a perfect choice to go with. 

Some disadvantages of NBR are poor ozone, sunlight and weather resistance as well as limited high temperature and flame resistance. For higher temperature resistance, a much better material to use is Silicone. 

 

Silicone 

Silicone compounds or “VMQ” offers a wide range of traditional operating temperatures starting at -40°C to 230°C . 

In addition to its excellent temperature resistance, it is also resistant to ozone, light, and weather conditions. Silicone can be typically found in the food and medical industry as well as in hydraulics and pneumatics. It is often the preferred material for o-rings, moulded parts and flat seals but is also commonly used for electric insulators due to the material’s translucency and flexibility. 

Although extremely flexible, silicone does have some disadvantages. Many silicone compounds have poor tensile strength, tear resistance, and abrasion resistance. If you are looking for a material that offers a higher tensile strength, while still offering high temperature resistance, look no further than Viton

 

Viton

In the rubber sealing material, its heat resistance (decomposition temperature greater than 300 degrees Celsius), oil resistance (various fuel, hydraulic oil, lubricating oil, synthetic oil), solvent resistance, climate resistance (resistance to line, ozone resistance, radiation resistance), chemical medium resistance is good, all surface sunny rubber, polyurethane rubber can not be used in high temperature environment or special working fluid, Fluorine rubber can be used as the material of the oil seal, no spontaneous combustion, no combustion-supporting, self-extinguishing in the event of fire, with good physical and mechanical properties, is the best comprehensive force of all synthetic rubber, commonly known as "rubber king" has become one of the indispensable and alternative basic materials in modern industry, especially in the field of high-tech.

However, its disadvantages are that the processing performance is not easy to master, the price is high, the cold resistance, the water resistance is poor, and the elasticity is poor at room temperature