Common Types of Oil Seal Materials

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

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 materials

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 −35° to 120 °C (−30° to 250 °F). 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 -60°C to 200°C (-140°F to 392°F). 

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® 

Viton®, a trademarked name of The Chemours Company, is a specific brand of synthetic rubber commonly used in o-rings, oil seals, gaskets, chemical resistant gloves, and other molded products. 

Due to having a higher density, Viton has the widest temperature range of -40°F to over 400°F (-40°C to over 240°C) making it a perfect choice for higher temperature applications. Viton® also has the largest range of chemical resistance, i.e., it is resistant to silicone oil and grease, mineral/vegetable oil and grease, aliphatic, aromatic, and chlorinated hydrocarbons, non-flammable hydraulic fuels as well methanol fuels, and more.

Although it does have a higher tensile strength and longer wear times than other materials, it is recommended to be used in dry-running applications sparingly or intermittently. 

While Viton offers a superior temperature and chemical range than other materials, it can be more expensive than the others as well. Let’s take a look at an alternative that is easier on the wallet, Polyacrylate. 

Polyacrylate is a great compromise between cost and quality. It has a high performing temperature and chemical range, but not to the extent of the range of Viton. The temperature ranges from 31°C to 148°C (-25°F to 300°F). Polyacrylate is primarily used in automotive transmissions and hoses but also found in shaft seals, gaskets and o-rings, due to offering a high resistance to hot oil and oxidation. While Polyacrylate is a great alternative to other high temperature resistant materials that are more expensive, it does have a poor water compatibility and cold flexibility. The best situation for Polyacrylate is an environment where heat and oil resistance but cost is the major issue. And while these 4 different materials cover a wide range of applications, there are even more materials out there designed for very specific niches in mind.

Summary

If you are looking for the highest temperature resistant oil seals, Perfluoelastomer can go up to 600°F. If you are more concerned for low temperature, Chloroprene can go all the way down to 40°F, which is why it is used most commonly for refrigeration. And if FDA applications or medical devices are your primary concern, Butyl , the all petroleum compound, will be your best choice. As you can see, when choosing the right material to work with, you must analyze several other key components to help choose the right one. 

Hopefully after reading this article, you have a better understanding of why choosing the right materials for oil seals is so important. Remember, if you have any questions about industrial oil seals and supplies, please contact us and we would be more than happy to help.

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In oil and gas applications, sealing devices are critical to prevent unwanted dirt, water, dust or other debris from contaminating products. When it comes to finding the right seal for these applications, material selection is key. Every rubber material has unique benefits that must align with the requirements in oil applications, such as chemical compatibility, temperature and pressure ranges.

Apple Rubber recommends the following rubber materials for oil applications. For more information about each material, visit our Material Selection Guide. 

Nitrile (Buna-N)

Nitrile is the sealing industries most economical and widely used material. It’s most commonly used in a wide range of oil applications, as well as automotive, marine, aircraft fuel and military applications. The most notable benefits of Nitrile for oil seals include: 

• Resistance to petroleum-based oil and fuel, silicone greases, hydraulic fluid and water

• Low compression set

• High tensile strength

• Excellent abrasion resistance

• Standard temperatures range from -40°F to 257°F

Fluorocarbon (Viton®)

Viton® is a synthetic rubber typically used in o-rings, gaskets, lip seals and other molded sealing devices for oil applications. High fluorine grades of Viton® offer excellent resistance to swell in high octane and oxygenated fuel blends, making it the ideal sealing material for ethanol/methanol blended gasoline. Other important benefits of Viton® include: 

• Standard temperatures range from -13°F to 446°F

• High temperature resistance

• Chemical resistance to transmission fluid, gasoline and petroleum oils

Silicone

Silicone offers one of the widest working temperature ranges of all elastomers. Silicone is most known for its flexibility and low compression set characteristics, making it an optimal choice for o-rings and other molded seals. The most important benefits of silicone in oil applications include: 

• Standard temperatures range from -85°F to 400°F

• Phenyl (PVMQ) based silicones can perform to -148°F

• Resistant to ozone, sun and weather conditions

• Flexibility allows Silicone to be a great option for electrical insulation

Fluorosilicone

Fluorosilicone combines the temperature stability of silicone with resistance to fuels, oils and solvents. Fluorosilicone is most often used in aerospace fuel applications and automotive fuel emission control, however it is becoming increasingly popular in a wider range of oil applications. Some of the unique characteristics of fluorosilicone include: 

• Standard temperatures range from 75°F to 400°F.

• Excellent high temperature resistance

• Offers good compression set properties

• Withstands exposure to sun, air and ozone

• Resistant to chlorinated and aromatic hydrocarbons

Want to talk more about sealing materials for oil applications?

Contact an engineer today. 

The Best Sealing Materials for Oil Applications