Technical Literature

Fluorosilicone Material Guide


When working in harsh environments like those common in the aerospace and automotive industries, it’s important to select a versatile, reliable sealing material. Fluorosilicone o-rings and seals are a great solution for many of the sealing challenges faced in these industries thanks to its high temperature range and resistance to many solvents and environmental elements. Learn more to see if fluorosilicone is the right sealing material for your next application.

What is Fluorosilicone?

Before examining fluorosilicone, it’s helpful to have an understanding of silicones in general. Silicones are a group of elastomers made from silicon, oxygen, hydrogen and carbon. These substances are very useful due to their flexibility and low compression set characteristics. They also have one of the widest working temperature ranges of all elastomers.

Like silicone, fluorosilicone rubber is a long-lasting, stable, compression set resistant elastomer that is usable across extreme temperature highs and lows. Unlike silicone, fluorosilicone has additional chemical resistance to non-polar solvents, fuels, oils, acids, and alkaline chemicals. Fluorosilicone offers greater resistance to fuel and oil than silicone, but is less resistant to hot air.

The unique properties of fluorosilicone make it a versatile material that is frequently used in the aerospace, automotive, and aviation industries for static sealing, low outgassing, and cushioning applications.

Fluorosilicone Trade Names
Trade Name Producer
FE Shin-Etsu
Elastosil Wacker
Silastic LS Dow
FSE Momentive

Fluorosilicone Features

Standard Compound Temperature Range:  -75°F to +400°F.

Hardness (Shore A):  40 to 80.

Fluorosilicone o-rings are generally blue in color and have a very long shelf-life.

Fluorosilicone is most often used in aerospace applications because of its high temperature fuel and diester-based lubricant resistance and stability. In addition to the aerospace industry, fluorosilicone is gaining popularity as a sealing solution for a wide range of applications across other demanding industries.

Among its many sought after properties, fluorosilicone demonstrates good compression set and resilience, and extreme resistance to air, sunlight, ozone, solvents, and chlorinated and aromatic hydrocarbons. This makes fluorosilicone o-rings a great sealing solution for harsh chemical environments and outdoor applications.

Fluorosilicone Designations
ASTM D2000/SAE J200 Type, Class FK
Apple Compound FS

Fluorosilicone Limitations

While ideal for static sealing applications, fluorosilicone is not generally recommended for dynamic sealing due to its limited physical strength, poor abrasion resistance, and high friction characteristics. It is also not recommended for exposure to brake fluids, hydrazine, aldehydes, amines, or ketones. 

Looking for Fluorosilicone seals?

If you have additional questions about material selection or ordering the right o-rings for your next project, look no further than Apple Rubber’s engineers.