FKM vs. NBR

Attribute	FKM	NBR
Chemical Resistance	Excellent	Good
Temperature Resistance	Excellent	Good
Compression Set	Low	High
Tensile Strength	High	Medium
Abrasion Resistance	Good	Excellent

Introduction

Fluoroelastomers (FKM) and nitrile rubber (NBR) are two commonly used elastomers in various industries due to their unique properties and applications. While both materials are known for their excellent resistance to oils, fuels, and chemicals, they have distinct differences that make them suitable for specific applications. In this article, we will compare the attributes of FKM and NBR to help you understand their differences and choose the right material for your needs.

Chemical Composition

FKM is a synthetic rubber made of fluorine, carbon, and hydrogen atoms. It is known for its exceptional resistance to high temperatures, chemicals, and oils. On the other hand, NBR is a synthetic rubber composed of acrylonitrile and butadiene. NBR offers good resistance to oils, fuels, and grease, making it a popular choice for automotive and industrial applications.

Temperature Resistance

One of the key differences between FKM and NBR is their temperature resistance. FKM can withstand high temperatures ranging from -20°C to 200°C, making it ideal for applications where heat resistance is crucial. In contrast, NBR has a lower temperature resistance, typically ranging from -40°C to 100°C. Therefore, if your application requires exposure to extreme temperatures, FKM would be the preferred choice.

Chemical Resistance

Both FKM and NBR offer excellent resistance to oils, fuels, and chemicals, but FKM has superior chemical resistance compared to NBR. FKM can withstand a wider range of chemicals, including acids, bases, and solvents, making it suitable for applications where exposure to harsh chemicals is common. NBR, on the other hand, may degrade when exposed to certain chemicals, so it is important to consider the specific chemical environment when choosing between the two materials.

Compression Set

Compression set refers to the ability of a material to return to its original shape after being compressed. FKM has a lower compression set compared to NBR, meaning it can maintain its shape and sealing properties over a longer period of time. This makes FKM a preferred choice for applications where sealing performance is critical, such as in automotive gaskets and O-rings. NBR, on the other hand, may experience permanent deformation over time, leading to reduced sealing effectiveness.

Abrasion Resistance

When it comes to abrasion resistance, FKM outperforms NBR due to its higher resistance to wear and tear. FKM is more durable and can withstand abrasive conditions, making it suitable for applications where mechanical wear is a concern. NBR, on the other hand, may wear out more quickly when exposed to abrasive environments, leading to shorter lifespan and potential failure.

Cost

Cost is another factor to consider when choosing between FKM and NBR. FKM is generally more expensive than NBR due to its superior properties and performance. While FKM offers excellent resistance to high temperatures, chemicals, and abrasion, it comes at a higher price point. NBR, on the other hand, is more cost-effective and widely used in various industries where high performance is not a primary concern.

Conclusion

In conclusion, FKM and NBR are two versatile elastomers with unique properties that make them suitable for different applications. While FKM offers superior temperature resistance, chemical resistance, compression set, and abrasion resistance, NBR is a cost-effective option with good resistance to oils and fuels. When choosing between FKM and NBR, it is important to consider the specific requirements of your application and select the material that best meets your needs.