FKM: The Complete Guide to High-Temperature & Chemical-Resistant Sealing | Polypac

FKM: The Premium Elastomer for Demanding Sealing Applications

When sealing applications push beyond the limits of standard materials—into realms of extreme heat, aggressive chemicals, or stringent safety requirements—a superior class of elastomer is required. Fluorocarbon Rubber (FKM), commonly known by the trade name Viton®, is that material. As a premium sealing solution, FKM offers an exceptional combination of high-temperature stability and broad chemical resistance that is unmatched by other general-purpose elastomers. For engineers facing demanding conditions, specifying FKM is a decisive step toward ensuring long-term reliability, safety, and performance.

At Polypac, with our ISO 9001 & IATF 16949 certified expertise in advanced sealing materials for special working conditions, we provide high-performance FKM components that are engineered to deliver where others cannot. This guide explores the unparalleled properties of FKM and its critical role in the world's most challenging industries.

What is FKM (Fluorocarbon Rubber)?

FKM is a family of synthetic fluorocarbon elastomers characterized by a saturated carbon-fluorine polymer backbone. This strong molecular bond is the source of its remarkable stability when exposed to high temperatures, aggressive fluids, and ozone. Unlike materials like NBR, FKM is specifically engineered for performance in hostile environments.

FKM seals are the definitive choice for applications demanding:

1. High-Temperature Operation: Continuous service where most rubbers would rapidly degrade.

2. Aggressive Fluid Compatibility: Sealing fuels, oils, chemicals, and solvents that attack standard elastomers.

3. Low Outgassing & High Purity: Suitable for vacuum and sensitive applications.

Exceptional Properties and Advantages of FKM

FKM's property profile justifies its position as a premium material:

1. Exceptional High-Temperature Resistance

FKM operates continuously at temperatures up to 200°C (392°F), with special grades capable of short-term exposure up to 230°C (446°F). This far exceeds the capabilities of NBR (+100°C) and EPDM (+150°C).

2. Outstanding Chemical and Fluid Resistance

FKM provides excellent resistance to a wide spectrum of challenging media, including:

• Aromatic hydrocarbons (benzene, toluene)

• Chlorinated hydrocarbons

• Mineral oils, fuels, and synthetic lubricants

• Many acids, bases, and aggressive additives

3. Excellent Resistance to Weathering and Ozone

The fluorinated backbone provides inherent, superior resistance to degradation from ozone, UV exposure, and weathering, making it suitable for both demanding indoor and outdoor applications.

4. Low Gas Permeability

FKM's dense molecular structure makes it an excellent barrier to gases and vapors, which is crucial for sealing in vacuum applications, emissions control, and volatile fluid handling.

5. Good Mechanical Properties at Elevated Temperatures

While not as abrasion-resistant as polyurethane at room temperature, FKM maintains good tensile strength, compression set resistance, and overall sealing force stability at high temperatures where other elastomers fail.

Understanding FKM's Limitations and Selection Criteria

Despite its strengths, FKM is not a universal elastomer. Proper application is key:

• Not for Steam or Hot Water: FKM performs poorly in these environments. EPDM is the preferred choice.

• Limited Low-Temperature Flexibility: Standard FKM stiffens below approximately -20°C (-4°F). Special low-temperature grades are available but involve trade-offs.

• Poor Performance with Certain Solvents: FKM swells and degrades in the presence of low molecular weight ketones (e.g., acetone), esters, and certain amines.

• Higher Cost: FKM is significantly more expensive than NBR or EPDM, making it a performance-driven investment.

Different Grades of FKM for Specific Challenges

Not all FKM is the same. Key classifications include:

• Type A (Standard FKM): Excellent all-around resistance to oils and fuels. The most common grade.

• Type B (Base-Resistant FKM): Formulated with enhanced resistance to amines and other aggressive additives found in modern engine oils and transmission fluids.

• Low-Temperature FKM: Modified to improve flexibility at sub-zero temperatures.

• Peroxide-Cured FKM: Offers superior chemical resistance, improved compression set, and lower outgassing, ideal for high-purity or high-temperature sealing.

The Polypac Advantage in FKM Technology

We ensure our FKM components deliver their full promised potential:

1. Precision-Grade Selection: Our technical team helps you navigate FKM grades to select the optimal one for your specific fluid, temperature, and mechanical requirements, ensuring you don't pay for unnecessary performance or risk failure from the wrong grade.

2. Precision Manufacturing & Post-Curing: FKM requires specific processing. We utilize precision molding and a controlled post-curing process, which is essential for developing the material's full thermal and chemical resistance and achieving a stable, low compression set.

3. Rigorous Quality Assurance: Every batch is subject to stringent quality checks, ensuring dimensional accuracy, material integrity, and consistent performance that critical applications demand.

Key Applications of FKM Seals

FKM is indispensable in industries where performance and safety are non-negotiable:

• Automotive & Transportation: Valve stem seals, turbocharger hoses, fuel injection system seals, and transmission components.

• Aerospace: Seals in fuel systems, hydraulics, and engine compartments.

• Chemical Processing: Pump seals, valve seals, and reactor gaskets handling aggressive chemicals.

• Oil & Gas: Downhole tool seals, manifold gaskets, and seals for exploration equipment.

• Semiconductor Manufacturing: Seals in wafer processing equipment requiring high purity and chemical resistance.