About What Are FKM Rubber Seals
FKM rubber seals, also known as fluorocarbon seals, are industrial seals made of fluorocarbon elastomer materials. Typically, these seals are used in aerospace, food and pharmaceutical, semiconductor manufacturing applications, etc. These types of seals are highly preferred in the above-mentioned industries due to properties such as high-temperature sustainability, chemical resistance, mechanical strength, etc. However, it is the Viton elastomer that is responsible for the superior performance of FKM seals. Therefore, one must be familiar with the fluorocarbon rubber material and its properties before using these seals in industrial applications. This article describes fluorocarbon rubber, its material properties, and the application and manufacturing process of FKM rubber seals.
An Overview of FKM (Fluorocarbon Rubber)
Fluorine rubber contains fluorine atoms. The C-F bond composed of fluorine atoms and carbon atoms has very high performance. At the same time, fluorine atoms have a great adsorption effect. Depending on this special molecular structure, fluorine rubber has excellent heat resistance and durability. Chemical resistance, solvent resistance, fluorination resistance, vacuum resistance, oil resistance, aging resistance, and other properties. Fluorine rubber was first used in the aviation field, but it is most widely used in the automotive field, accounting for 60% to 70% of the total application. Therefore, from a practical application perspective, it is very important to ensure that the appropriate fluororubber is selected.
Based on their chemical composition, FKM can be divided into the following types:
Type 1 FKM consists of vinylidene fluoride (VDF) and hexafluoropropylene (HFP). Copolymers are the standard type of FKM and offer good overall properties. Their fluorine content is approximately 66% by weight.
Type 2 FKM consists of VDF, HFP, and tetrafluoroethylene (TFE). Compared to copolymers, terpolymers have a higher fluorine content (typically between 68 and 69% fluorine), resulting in better chemical and thermal resistance. Compression sets and low-temperature flexibility may be negatively affected.
Type 3 FKM consists of VDF, TFE, and perfluoromethyl vinyl ether (PMVE). The addition of PMVE provides better low-temperature flexibility compared to copolymers and terpolymers. Typically, the fluorine content of Type 3 FKM ranges from 62 to 68 %.
Type 4 FKM consists of propylene, TFE, and VDF. Although the base resistance of Type 4 FKM increases, their expansion properties (especially in hydrocarbons) become worse. Typically, their fluorine content is approximately 67% by weight.
Type 5 FKM consists of VDF, HFP, TFE, PMVE, and ethylene. Known for its resistance to alkali and hydrogen sulfide high temperatures.
Characteristics of Fluorocarbon Elastomers
Fluorocarbon elastomers are highly fluorinated, carbon-backboned polymers used in applications to resist harsh chemical and ozone attacks with a thermal stability of 500°F (262°C). Fluorocarbons also offer a low compression set and excellent aging characteristics. FKM elastomers provide excellent service in oil, gasoline, hydraulic fluids, hydrocarbon solvents, and extended fuels.
The popularity of fluorocarbon rubber comes from the material’s vast range of benefits. Most notably, it has an excellent temperature resistance and operates between -26°C and 225°C. Other benefits include:
■ Excellent atmosphere aging, oxidation, heat, flame, diluted acid, concentrated acid, and oil and gasoline resistance.
■ Excellent solvent resistance hydrocarbons.
■ Good to excellent permeability.
■ Good tear, abrasion, moisture, animal oil, and vegetable oil resistance.
■ Good dielectric properties.
■ Good to fair compression set.
What Are FKM Rubber Seals Commonly Used For?
Aerospace: Today, the vast majority of the world’s commercial and military aircraft rely on the reliability and performance of FKM and FFKM seals and parts. Seals made of FKM are commonly used in turbine engines, auxiliary power units, and hydraulic actuators. These include O-rings for line fittings, connectors, valves, pumps, and reservoirs.
Automotive field: FKM rubber seals are widely used in the sealing of engines, fuel systems, transmission systems, and other parts. It can effectively prevent oil leakage, gas leakage, and other problems, and improve the reliability and safety of the car. At the same time, due to the excellent oil resistance of FKM rubber seals, catalytic converters, oxygen sensors and other components in automobile exhaust after-treatment systems have also been widely used.
Food and Dairy: FKM, EPDM, and silicone materials are suitable where seal failure could lead to potential contamination or production line disruption. Also complies with regulations such as CIP (Clean in Place), SIP (Sterilize in Place), and FDA, 3-A, NSF, and USP standards.
Instrumentation and Electronics: Semiconductor manufacturers recognize the quality of FKM because of its ability to withstand a wide range of corrosive chemicals while also withstanding the high temperatures of the wafer manufacturing process.
Medical: Clean pumps, tanks, valves, heat exchangers, and equipment using clean-in-place and disinfect-in-place protocols.
Racing and Pro Automotive: Fuel Seals, Cylinder Head and Intake Manifold Gaskets, Quick Connect O-Rings, Fuel Injection Seals.
Subsea, Oil, and Gas: FKM rubber seals are critical components in oil and gas systems with HP/HT safety requirements and strong resistance to rapid gas decompression requirements.
How To Choose the Right FKM Rubber Seals for Your Specific Application
There are several important factors to consider when selecting a rubber seal for your specific application. These factors will ensure you choose the right material that will meet the requirements of your specific environment.
1. Temperature range and pressure requirements:
- Evaluate the temperature range to which the seal or gasket is exposed.
- Consider the pressure requirements of your application.
- Choose materials that can effectively handle temperature and pressure conditions.
2. Chemical exposure:
- Evaluate the compatibility of the seal or gasket material with the different fluids and gases it may come into contact with.
- Determine if there will be any exposure to chemicals or corrosive substances.
- Choose materials that are resistant to chemical degradation.
3. Operating conditions:
- Evaluate any specific operating conditions such as vibration, UV exposure, or mechanical stress.
- Make sure the seal or gasket material chosen can withstand these conditions without deterioration.
By carefully considering these factors, you can make an informed decision when selecting FKM rubber seals for your specific application. This will help ensure optimal performance, longevity, and reliability of your equipment or machinery.
The Manufacturing Process of FKM Rubber Seals
The manufacturing process of FKM rubber seals mainly includes compression molding, injection molding, extrusion molding, etc. Among them, compression molding is one of the most commonly used manufacturing processes. By selecting the appropriate mold and raw materials, the FKM rubber raw materials are heated and softened and then put into the mold to exert a certain pressure to mold it into the desired shape. This process can manufacture seals of various shapes, such as O-rings, U-rings, V-rings, etc.
Injection molding and extrusion are suitable for the manufacture of seals with complex shapes. Injection molding is to heat and melt the FKM rubber raw material, inject it into the mold through high pressure, and cool it to obtain the required seal. Extrusion, on the other hand, is a seal in which the FKM rubber raw material is heated and softened and then extruded into the desired shape by an extruder. These processes can create more complex seal shapes such as gaskets, sealing strips, etc.
Summary
As a key material for high-performance and multi-field applications, FKM rubber seals play an important role in modern industry. In the future, with the continuous advancement of technology and the continuous expansion of application fields, FKM rubber seals will show their unique charm in more fields.
