Fluorosilicone (FVMQ)

What is Fluorosilicone

Fluorosilicone is a specialised elastomer that combines the wide temperature resilience of silicone with the stronger fuel, oil, and solvent resistance more commonly associated with fluorocarbon rubbers. Under ASTM D1418 it is designated as FVMQ.

Fluorosilicone O-rings, gaskets, and mouldings are commonly supplied in blue or light blue by industry convention.

Because of this hybrid performance profile, Fluorosilicone is often selected for demanding static sealing applications where exposure to fuels, oils, solvents, and temperature extremes must all be managed together.

Key Properties & Performance Profile

Fluorosilicone offers a useful balance of thermal stability, chemical resistance, and electrical performance, but it should still be selected with its mechanical limits in mind.

• Broad temperature range — Typical continuous service ranges are around -55°C to +205°C, which makes Fluorosilicone suitable for both very low and elevated temperature environments.
• Excellent fuel, oil, and solvent resistance — It performs well in automotive and aviation fuels, mineral and synthetic oils, and many non-polar chemical media.
• Good weathering, ozone, and UV resistance — Outdoor exposure, sunlight, and environmental ageing are generally handled well.
• Stable mechanical and elastic properties over temperature — Elongation and resilience remain relatively stable over a wide operating range, which is useful in thermally cycled static seals and diaphragms.
• Good dielectric properties — Like silicone, Fluorosilicone remains a capable electrical insulator for applications where electrical isolation matters.
• Static seal suitability — It is commonly selected for O-rings, gaskets, seals, diaphragms, and mouldings used in static interfaces.

Typical Grades, Standards & Physical Characteristics

Fluorosilicone is available in a range of Shore A hardnesses and can be supplied as O-rings, gaskets, sheets, and custom mouldings depending on the sealing requirement.

Typical physical values for many FVMQ compounds include tensile strength up to around 9 MPa and elongation at break roughly in the 200% to 400% range, although exact figures depend on the specific formulation and supplier.

Common Applications & Use Cases

Because of its combination of chemical and thermal resilience, Fluorosilicone is often used in:

• Aerospace and aviation seals, gaskets, and O-rings used in aircraft fuel systems, hydraulic systems, and di-ester lubrication duties.
• Automotive fuel-system seals, diaphragms, and static sealing components in engines or fuel delivery systems.
• Industrial and chemical-processing seals in tanks, pipes, and housings exposed to oils, petroleum-based fluids, or mild chemical media.
• Outdoor and environmentally exposed applications where ozone, UV, and weathering resistance are required.
• Static sealing systems such as O-rings, gaskets, diaphragms, and flat seals in flanges, housings, and fixed interfaces.

Due to limited physical strength, poor abrasion resistance, and higher friction characteristics, Fluorosilicone is not generally recommended for demanding dynamic sealing such as rotary shafts, reciprocating pistons, or other high-wear movement-heavy duties.

Design & Selection Considerations

When specifying Fluorosilicone seals, designers should:

• Review the chemical environment carefully — although Fluorosilicone performs well with fuels, oils, hydrocarbons, and many non-polar solvents, it is not suitable for every fluid.
• Use it for static sealing wherever possible — static O-rings, gaskets, and flange seals are far better suited than dynamic or abrasive sealing duties.
• Select hardness to suit the application — softer grades may improve sealing on irregular surfaces or at low temperature, while harder grades can offer more sealing force and durability.
• Consider gas permeability and mechanical limits — if the duty requires very high mechanical loads, extreme abrasion resistance, or high gas-tightness, another elastomer or a composite sealing solution may be more suitable.
• Verify actual supplier data — final properties depend on formulation, fillers, cure system, and source compound, so data sheets should always be checked before release.

Summary — Why Choose Fluorosilicone

Fluorosilicone is a versatile high-performance elastomer that brings together the thermal flexibility and dielectric benefits of silicone with the improved resistance to fuel, oil, and solvents often associated with fluorocarbon materials.

It is particularly well suited to static sealing applications in aerospace, automotive, industrial, and chemical-service environments where exposure to fuels, oils, solvents, and wide temperature ranges are all part of the design envelope.

Fluorosilicone is not recommended for exposure to brake fluids, hydrazine, or ketones, and it should not be treated as a general-purpose solution for high-wear dynamic sealing.

Compliance & Quality Considerations

Eastern Seals (UK) Ltd sources Fluorosilicone compounds from approved manufacturers, and exact properties can vary according to hardness, cure chemistry, filler package, and supplier formulation.

The information on this page should be used as a selection guide only. For critical applications, confirm media compatibility, service temperature, regulatory requirements, and final compound performance against the exact operating conditions before sign-off.