Custom FKM (Viton™) Moulding:
High Performance Seals & Components

We specialize in custom FKM (Viton™) moulding to create high-performance seals and components that offer exceptional resistance to extreme temperatures, chemicals, and fuels

Fluoroelastomer (FKM) Components Engineered for the Most Extreme Environments

Viking Extrusions excels in custom FKM rubber moulding, producing elite components for applications where failure is not an option. We work with high-performance Fluoroelastomers (FKM), most famously known by the Chemours trade name Viton™, to manufacture parts that withstand extreme heat, aggressive chemicals, and high pressures. Using injection, compression, and transfer moulding, we deliver seals, gaskets, and custom parts that provide ultimate reliability in the harshest conditions.

What is FKM (Viton™) Rubber Moulding?

FKM moulding is a specialised manufacturing process focused on creating parts from fluoroelastomers—a family of high-performance synthetic rubbers. FKM is the official ASTM designation for this polymer class, while Viton™ is the most widely recognised brand name, and the terms are often used interchangeably.

The process involves shaping the raw FKM compound in a highly precise mould using heat and pressure. Due to its unique chemistry, FKM almost always requires a multi-stage curing process. After the initial moulding, a secondary post-curing phase in a controlled oven is performed to complete the chemical cross-linking, ensuring the final part achieves its maximum thermal stability, chemical resistance, and optimal physical properties.

The source of FKM’s incredible performance is its molecular structure, which is saturated with fluorine. The carbon-fluorine bond is one of the strongest chemical bonds, giving the material its exceptional resistance to being broken down by heat, chemicals, or oxidation.

Our FKM (Viton™) Rubber Availability

View the table below for a detailed breakdown of the available colours, hardness ranges, and specialist grades for FKM (Viton™) and other common elastomers we offer.

Material	Available Colours	Hardness (Shore A)	Specialist Grade Availability
EPDM	Black (standard), Blue, Biege	35 - 90	FDA, WRAS,Flame Retardant, EN45545-2, Antistatic/Conductive, Oil-Resistant,
Nitrile (NBR)	Black, (standard) Blue, Red, Brown	40 - 90	HNBR, XNBR, FDA, Metal Detectable, BS2751
Natural Rubber (NR)	Black (standard)	35 - 90	FDA, Construction BS1154
Neoprene (CR)	Black (standard)	50 - 85	Flame Retardant, BS2752
FKM (Viton™)	Black (standard), Blue, Brown	50 - 90	FDA
Silicone (VMQ)	Translucent (natural) , All Colours	20 - 80	FDA, WRAS, Platinum Cured, Metal Detectable, Flame Retardant, EN45545-2

Key Properties & Advantages of Moulded FKM

Choosing FKM for your moulded components provides an unparalleled level of performance for mission-critical applications where other elastomers would rapidly fail.

Exceptional High-Temperature Performance

FKM is engineered to perform where others cannot. It has an outstanding continuous service temperature range, typically from -20°C up to +205°C (-4°F to +401°F). It can also withstand intermittent exposure to even higher temperatures, maintaining its sealing force and mechanical properties far beyond the limits of NBR, EPDM, or Neoprene.

Unmatched Chemical & Fuel Resistance

This is FKM’s defining feature. It provides excellent resistance to an incredibly broad spectrum of aggressive media, including:

Petroleum oils and hydrocarbon fuels (including biodiesel and oxygenated fuels).
Concentrated acids and solvents.
Mineral acids and halogenated hydrocarbons.
Silicone oils and greases. This makes it indispensable in the chemical processing, aerospace, and high-performance automotive industries.

Superior Sealing in Harsh Environments

Moulded FKM parts are superb long-term sealing solutions. They possess a very low compression set, meaning they retain their original shape and sealing force even after prolonged compression at high temperatures. Furthermore, FKM has very low gas permeability, making it an excellent choice for vacuum applications and for sealing gases and volatile fluids.

Excellent Weathering & Environmental Resistance

FKM is virtually immune to degradation from atmospheric conditions. It offers superior resistance to ozone, UV radiation, and general weathering, ensuring exceptional longevity in any environment without cracking or becoming brittle.

Important Limitations to Consider

While FKM is a top-tier performer, it’s critical to understand its limitations for proper application:

High Cost: FKM is a premium material, and its cost is significantly higher than general-purpose elastomers. Its use must be justified by the extreme performance requirements of the application.

Poor Low-Temperature Flexibility: Standard FKM grades can lose flexibility and become stiff at temperatures below -20°C (-4°F). Specialised, more expensive low-temperature grades are required for colder applications.

Vulnerability to Specific Chemicals: FKM is not resistant to ketones (like acetone, MEK), esters, amines, and certain specialised hydraulic fluids (like Skydrol).

Compare the Properties of FKM (Viton™) Against other Elastomers

Explore this comprehensive comparison table detailing the resistance, temperature range, and mechanical performance of FKM (Viton™) compared to common elastomers like Neoprene, Silicone, Nitrile, and $EPDM$ for various industrial applications.

Property	Neoprene (CR)	Nitrile (NBR)	EPDM	Natural Rubber	FKM (Viton™)	Silicone (VMQ)
Primary Attribute	Versatile All-Rounder	Oil and Fuel Resistant	Weather & Water Resistant	High Mechanical Strength	Extreme Heat and Chemical Resistant	Extreme Temperature Range
Abrasion Resistance	⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐⭐	⭐
Tear Resistance	⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐	⭐⭐
Tensile Strength	⭐⭐⭐⭐	⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐⭐⭐	⭐⭐
Resilience / Rebound	⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐	⭐⭐⭐
Weather / Ozone / UV	⭐⭐⭐⭐	⭐	⭐⭐⭐⭐⭐	⭐	⭐⭐⭐⭐⭐	⭐⭐⭐⭐⭐
Water & Steam Resistance	⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐
Oil & Fuel Resistance	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐	⭐	⭐⭐⭐⭐⭐	⭐
Acid & Alkali Resistance	⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐⭐	⭐⭐⭐⭐⭐	⭐⭐⭐
Flame Resistance	⭐⭐⭐⭐	⭐	⭐	⭐	⭐⭐⭐⭐⭐	⭐⭐⭐⭐
Temperature Range (Typical)	-40°C to 120°C	-35°C to 120°C	-50°C to 150°C	-50°C to 80°C	-20°C to 205°C	-60°C to 200°C
Cost	£££	££	£££	£	£££££	££££

FKM Moulding Processes

Moulding FKM requires specialised knowledge and equipment to manage its unique curing characteristics and ensure maximum performance.

FKM Injection Moulding

The preferred method for high-volume, precision FKM components.

The Process: Raw FKM is injected into a heated, closed mould under high pressure. This is followed by a carefully controlled post-curing process outside of the press.
Advantages: High efficiency for large quantities, excellent for complex geometries, and superior part-to-part consistency.
Best For: Automotive fuel injector seals, aerospace O-rings, and high-volume industrial seals.

FKM Compression Moulding

A reliable and versatile process, well-suited for larger parts and prototyping.

The Process: A pre-form of FKM is placed in the mould cavity and cured under intense heat and pressure. A secondary post-cure is then performed in an oven.
Advantages: Lower tooling investment, ideal for large-diameter O-rings and gaskets, and suitable for prototyping and smaller production runs.
Best For: Large chemical processing gaskets, valve seats, and custom-designed seals.

FKM Transfer Moulding

This method provides a bridge between compression and injection, allowing for more complex designs with inserts.

The Process: FKM is forced from a transfer pot into the closed mould cavities, allowing for more intricate shapes and the bonding of FKM to metal components.
Advantages: Excellent for moulding parts with metal inserts, tighter tolerances than compression moulding.
Best For: Rubber-to-metal bonded seals, complex valve components, and custom-engineered parts.

Precision-Engineered FKM Moulded Components

Explore our core range of custom FKM (Fluoroelastomer) components, specifically engineered to deliver superior, long-term performance in the most chemically aggressive and high-heat environments. These parts leverage FKM’s exceptional resistance to aliphatic and aromatic hydrocarbons, concentrated acids, and extreme operating temperatures, making them indispensable for aerospace seals, chemical processing gaskets, and aggressive fuel system components. View our key moulded seals and bellows below, all manufactured with precision for high-integrity sealing and protection.

Applications & Industries We Serve

FKM is the material of choice for the most challenging sealing applications across elite industries:

Aerospace & Defence

The default choice for O-rings and seals in jet engines, fuel systems, and hydraulic actuators due to its resistance to jet fuel and extreme temperatures.

Chemical Processing Industry

Used for gaskets, pump diaphragms, and valve seals that handle aggressive chemicals, acids, and high-temperature process fluids.

Oil & Gas Exploration

Essential for seals, packers, and O-rings in downhole equipment where resistance to sour gas (H2S), high temperatures, and aggressive drilling chemicals is required.

High Performance Automotive

Critical for fuel injector O-rings, crankshaft seals, and fuel pump seals that must withstand modern, aggressive fuel blends and high engine temperatures.

Pharmaceutical & Semiconductor

Used for high-purity seals in processing equipment that involves aggressive plasma, wet chemical etching, and cleaning agents.

Power Generation

Specified for flue gas desulphurisation (FGD) expansion joints, valve stem seals, and turbine lubrication system gaskets. It has unparalleled resistance to high heat, corrosive chemicals.

Frequently Asked Questions About FKM (Viton®) Moulding

Is Viton™ the same thing as FKM?

Yes, for all practical purposes. FKM is the generic name for the fluoroelastomer polymer family, as designated by ASTM. Viton™ is the registered trademark for the FKM brand originally developed by DuPont (now Chemours). While other companies make FKM, Viton™ is the most recognised name.

When should I choose FKM over a cheaper material like Nitrile (NBR)?

You should upgrade to FKM when the application conditions exceed the limits of NBR. This typically involves temperatures consistently above 120°C (250°F), or exposure to aggressive chemicals, oxygenated fuels, ozone, or UV light that would cause NBR to degrade and fail.

What is the absolute maximum temperature FKM can handle?

While the continuous operating limit is around 205°C (401°F), many FKM grades can survive short-term intermittent exposure to temperatures as high as 260°C (500°F).

Can FKM parts be used in vacuum or high-pressure environments?

Yes, FKM’s low gas permeability and excellent compression set make it ideal for vacuum and high-pressure sealing.

Are there colour options for FKM mouldings?

While black is standard, FKM can be produced in a range of colours for identification or aesthetic purposes

Why Choose Viking Extrusions?

Fluoroelastomer Expertise

Our team specialised in high performance FKM compounds. We guide you in choosing the right grade for your specific application.

Mission-Critical Quality & Traceability

With ISO 9001 certification, we ensure full traceability and rigorous testing for our FKM parts.

Agile Production for Demanding Applications

We combine speed with precision to deliver FKM components on time, even for complex geometries and tight tolerances.

Strategic Technical Partnership

We support you from concept to completion, solving complex sealing challenges with precision-engineered FKM solutions.

Looking for FKM (Viton®) moulded parts?

Let our experts help you manufacture the perfect custom component.

Custom FKM (Viton™) Moulding: High Performance Seals & Components