FKM vs. HNBR

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

Introduction

Fluoroelastomers (FKM) and Hydrogenated Nitrile Butadiene Rubber (HNBR) are two popular elastomers used in various industries for their excellent chemical resistance, high temperature stability, and durability. While both materials have similar properties, there are key differences that make them suitable for different applications.

Chemical Composition

FKM is a synthetic rubber made of fluorine, carbon, and hydrogen atoms. It is known for its exceptional resistance to chemicals, oils, and high temperatures. On the other hand, HNBR is a hydrogenated version of Nitrile Butadiene Rubber (NBR), which contains hydrogen atoms added to the polymer chain. This hydrogenation process improves the material's resistance to heat, ozone, and chemicals.

Temperature Resistance

FKM has a higher temperature resistance compared to HNBR, with a continuous operating temperature range of -20°C to 200°C. This makes FKM ideal for applications where high temperatures are a concern, such as in automotive engines and aerospace components. HNBR, on the other hand, has a lower temperature resistance with a continuous operating temperature range of -40°C to 150°C, making it suitable for applications where moderate heat resistance is required.

Chemical Resistance

Both FKM and HNBR exhibit excellent resistance to a wide range of chemicals, including oils, fuels, acids, and solvents. FKM, however, has superior resistance to harsh chemicals such as acids and bases, making it the preferred choice for applications where exposure to corrosive substances is common. HNBR, on the other hand, is more resistant to ozone and weathering, making it suitable for outdoor applications.

Compression Set

FKM has a lower compression set compared to HNBR, meaning it can maintain its shape and sealing properties over a longer period of time. This makes FKM ideal for applications where long-term sealing performance is critical, such as in hydraulic systems and industrial seals. HNBR, on the other hand, has a higher compression set, which may result in reduced sealing effectiveness over time.

Abrasion Resistance

Both FKM and HNBR have good abrasion resistance, making them suitable for applications where wear and tear are common. FKM, however, has slightly better abrasion resistance compared to HNBR, making it the preferred choice for applications where resistance to mechanical wear is essential, such as in seals and gaskets in heavy machinery. HNBR, on the other hand, may exhibit signs of wear more quickly in high-stress environments.

Conclusion

In conclusion, FKM and HNBR are both excellent elastomers with unique properties that make them suitable for a wide range of applications. While FKM offers superior temperature resistance, chemical resistance, and compression set properties, HNBR excels in ozone resistance and weathering. The choice between FKM and HNBR ultimately depends on the specific requirements of the application, such as temperature range, chemical exposure, and sealing performance.