FKM vs FPM vs Viton: What’s the Difference? (2026 Guide)

Key Takeaways (TL;DR)

• FKM and FPM are the same material — just ASTM D1418 (USA/Asia) vs ISO 1629 (Europe) naming.
• Viton® is a Chemours trademark for FKM: all Viton is FKM, but not all FKM is Viton.
• For most B2B sealing, specify FKM by ASTM D2000 grade — identical performance without the brand premium.
• Reserve named Viton® for aerospace, medical, or safety-critical specs that require Chemours traceability.
• Properties: −20 to +200°C (GLT to −40°C, peroxide to +230°C); excellent oil/fuel/acid resistance; poor vs ketones, esters, amines.

The Short Answer

FKM and FPM are the SAME material — they just use different naming standards. Viton® is a premium brand of FKM made by Chemours (formerly DuPont).

Term	What It Is	Who Defines It
FKM	Standard chemical name for fluoroelastomer	ASTM International (USA)
FPM	Same material, different standard	ISO (Europe)
Viton®	A branded, high-quality type of FKM	Chemours (USA)

If you’ve ever shopped for high-performance rubber seals, you’ve probably come across the terms FKM, FPM, and Viton — often used as if they’re interchangeable. But are they really the same thing?

The short answer: they refer to the same base material (fluoroelastomer), but they are not identical in practice. Understanding the distinction can save you from costly specification errors.

In this guide, we’ll break down exactly what each term means, where they overlap, and how to choose the right one for your application.

What Is FKM?

FKM is the ASTM D1418 designation for fluoroelastomer rubber. The “F” stands for fluorine, and “KM” denotes a rubber with saturated backbone and copolymer structure.

Key characteristics of FKM:

• Temperature range: -20°C to +200°C (standard grades), with special grades reaching +230°C
• Chemical resistance: Excellent resistance to oils, fuels, acids, and many solvents
• Compression set: Low, making it ideal for long-term sealing
• Hardness range: Typically 50–90 Shore A

FKM is the most commonly used technical term in North America and Asia when specifying fluoroelastomer materials.

What Is FPM?

FPM is the ISO 1629 designation for the same fluoroelastomer material. The letters stand for:

• F = Fluoro (containing fluorine)
• P = Propylene (copolymer component)
• M = Methylene (saturated backbone)

So when a European engineer specifies “FPM O-rings” and an American engineer asks for “FKM/Viton O-Rings,” they’re asking for the exact same material — just using different naming standards.

Naming System	Designation	Region
ASTM D1418	FKM	USA, Asia
ISO 1629	FPM	Europe
DIN/EN 682	FPM	Germany, EU

What Is Viton?

Viton® is a registered trademark of The Chemours Company (formerly DuPont). It is a specific brand of FKM fluoroelastomer.

Think of it this way: all Viton is FKM, but not all FKM is Viton. This is exactly like the relationship between “Kleenex” and “facial tissue” — Viton is the brand name that has become synonymous with the material category.

Viton comes in several grades, each optimized for different conditions:

Viton Grade	Type	Key Feature
Viton A	Copolymer (VDF/HFP)	General-purpose, most common
Viton B	Terpolymer (VDF/HFP/TFE)	Better chemical resistance
Viton F	Terpolymer (VDF/HFP/TFE)	Superior fuel and oil resistance
Viton GLT	Low-temperature	Service down to -40°C
Viton GFLT	Low-temp + fuel resistant	Combines low-temp with fuel resistance

FKM vs FPM vs Viton: Quick Comparison

Factor	FKM	FPM	Viton
What it is	Material standard (ASTM)	Material standard (ISO)	Brand name (Chemours)
Scope	All fluoroelastomers	All fluoroelastomers	Chemours-made fluoroelastomers only
Geographic usage	North America, Asia	Europe	Worldwide (brand recognition)
Quality guarantee	Varies by manufacturer	Varies by manufacturer	Consistent Chemours quality
Cost	Moderate to high	Moderate to high	Premium (brand premium)
Availability	Many manufacturers	Many manufacturers	Chemours-authorized only

Do These Differences Matter for Your Project?

For most sealing applications, the practical answer is no — they perform identically when the compound formulation is equivalent. Here’s when it matters:

When to Specify Viton by Name

• Your industry requires Chemours-certified material (aerospace, some OEM specifications)
• Your customer explicitly mandates Viton® in their material specification
• You need traceability to a specific compound datasheet

When FKM (Generic) Is Sufficient

• Your specification only requires fluoroelastomer performance per ASTM D2000
• You need a cost-effective solution without brand premium
• Your application uses standard chemical and temperature ranges

When to Use the FPM Designation

• You’re working with European standards (DIN, EN)
• Your engineering documentation follows ISO conventions
• You’re specifying for EU-based procurement

FKM Material Properties Reference

Regardless of which name you use, here are the typical material properties for standard FKM/FPM/Viton:

Property	Value
Hardness range	50–90 Shore A
Tensile strength	8–20 MPa
Elongation at break	100–300%
Max continuous service temp	+200°C
Min service temp	-20°C (standard), -40°C (GLT grades)
Specific gravity	1.80–1.95
Compression set (22h @ 175°C)	15–25%

Common Applications

FKM/FPM/Viton seals are used across industries that demand reliable performance in harsh environments:

• Automotive: Fuel system seals, valve stem seals, crankshaft seals
• Aerospace: O-rings for hydraulic and fuel systems
• Oil & Gas: Downhole seals, wellhead sealing components
• Chemical processing: Gaskets and seals for aggressive media
• Semiconductor: Seals for plasma and chemical vapor deposition equipment

How to Choose the Right FKM Seal for Your Application

1. Define your operating conditions — temperature range, chemical exposure, pressure
2. Check chemical compatibility — FKM resists many fluids but not ketones, esters, or amines
3. Select the right grade — A-type for general use, B/F-type for aggressive fuels, GLT for low temperatures
4. Specify by performance, not just name — Reference ASTM D2000 callouts (e.g., M2HK810 A2-10) for precision
5. Work with a manufacturer who can provide compound data — Certified material datasheets ensure consistency

Viton® Brands, Grades & Temperature Limits

Not all FKM is created equal. Viton® is the original and most trusted brand, but several qualified alternatives exist:

• Viton® (Chemours) — original inventor, consistently high quality, premium price
• Daikin (Dai-El) — Japanese brand, excellent quality
• AGC (Fluorel) — Japanese, strong in the Asia-Pacific market
• Solvay (Tecnoflon) — European brand, strong chemical resistance
• Generic Chinese FKM — quality varies widely; request third-party test reports

Premium Viton® vs Standard FKM: When to Choose

• Choose Viton® or branded FKM for aerospace, medical, or safety-critical applications
• Standard quality FKM is sufficient for most automotive, industrial, and oil & gas sealing
• Always request SGS or material test reports regardless of brand

Temperature & Chemical Resistance

• Temperature: −26°C to +205°C (some specialty grades to +230°C)
• Chemical resistance: excellent against oils, fuels, lubricants, mineral acids, and many organic solvents
• Limitations: poor resistance to ketones, esters, and some brake fluids (DOT 5)

Buying FKM Seals from China: Key Checklist

• Request material data sheets (TDS) and SGS test reports
• Verify fluorine content — quality FKM should be 66%+ fluorine
• Confirm hardness (typically 75 Shore A for O-rings)
• Request samples for temperature/chemical testing before bulk orders
• Minimum order: start with 100–500 pieces for testing

Anlintech supplies FKM/Viton® seals and O-rings with optional third-party test reports. Contact us for a free material recommendation.

Real-World Example

A procurement team issued a drawing calling for “Viton® O-rings” for a hydraulic manifold. The approved supplier could only certify generic FKM to ASTM D2000 M2HK. Rather than pay the Viton® brand premium, the engineer confirmed the operating envelope (−10 to +180°C, mineral oil, no fuel) fell well inside standard FKM performance and re-specified to “FKM per ASTM D2000 M2HK710”. The seals performed identically at roughly 30% lower material cost, with full lot traceability. The case shows the right move is to specify by performance grade, reserving the brand name for where a spec or regulator actually demands it.

Standards & Further Reading

The naming itself is standardized: ASTM D1418 assigns “FKM”, ISO 1629:2013 assigns “FPM”, and material grades are specified by ASTM D2000 callouts. For brand-specific data, see the Chemours Viton® technical library.

Conclusion

FKM, FPM, and Viton all refer to fluoroelastomer rubber, but they differ in naming convention and brand specificity. FKM is the ASTM term used in North America, FPM is the ISO equivalent in Europe, and Viton is a premium brand of FKM made by Chemours.

For most B2B sealing applications, specifying FKM with your required ASTM D2000 grade is sufficient — and it avoids the brand premium of Viton while delivering identical performance.

Need custom FKM seals manufactured to your specifications? Anlintech produces FKM/Viton seal rings and gaskets with full material traceability. Contact us for a quote.

Explore our Custom Rubber Parts for materials, specifications, and custom manufacturing options.