Seal Materials

The material the seal is made from is tailored to your application requirements. We start by understanding the media, pressures, temperatures, dynamic conditions, mating surfaces, tolerancing, required lifetime and so on. Darcoid maintains an extensive database of materials optimized for specific use applications. Based on your inputs during a simple onboarding conversation, our engineers will quickly zero in on the formulations that will pass your project statement of requirements (SOR).

“Rubber” is a broad term for polymer-based compounds that are cured, or vulcanized, to form thermoset elastomers. These materials are grouped into more than a dozen major elastomer families, and within each family there can be hundreds of individual formulations engineered for specific operating conditions and performance requirements.

Common and specialty elastomer families include:

FKM fluorocarbon elastomers, including Viton™
EPDM / EPR
NBR / Buna-N
HNBR
XNBR
Polyurethane (AU)
Silicone (VMQ / LSR)
Fluorosilicone (FVMQ)
Butyl (IIR)
AFLAS® / FEPM
FFKM perfluoroelastomers, including Kalrez®, Chemraz®, Parofluor®, Ultra®, and Perlast®

Within each polymer family, formulations can be optimized for properties such as wear resistance, extrusion resistance, low compression set, low-temperature flexibility, reduced friction, and explosive decompression resistance (EDR).

The right material depends on more than the polymer family alone. Compound formulation, media compatibility, temperature, pressure, motion, hardware design, regulatory requirements, and expected service life all influence seal performance.

Regulatory and industry requirements

Many elastomer compounds are available in formulations designed to support regulatory and industry requirements such as FDA 21 CFR 177.2600, USP Class VI, 3-A sanitary requirements, WRAS, and animal-derived ingredient (ADI) declarations.

For FDA food-contact applications, compliance depends on the specific compound and intended use. Under 21 CFR 177.2600, applicable requirements may include:

Paragraphs A–D: Ingredient and quantitative limitations; generally associated with dry food applications
Paragraphs A–E: Includes extraction testing for dry and aqueous food-contact applications
Paragraphs A–F: Includes requirements applicable to dry, aqueous, and fatty food-contact applications

Specific regulatory status should always be confirmed for the exact compound and application before specification.

And engineered thermoplastics

Where media, pressures, and dynamics drive material selection beyond elastomers we move into engineered thermoplastics and metals (PTFE Teflon^TM, PEEK, Delrin^TM  acetal resin polyoxymethylene (POM), polyimide Vespel^TM, PFA, FEP, ETFE, ECTFE, PCTFE, PVDF, etc.).

Engage with our technical team to take the guesswork out of material selection.

Aflas is a registered trademark of Asahi Glass Co., Ltd
Chemraz is a registered trademark of Greene, Tweed Technologies, Inc.
Delrin is a registered trademark of Dupont Polymers, Inc.
Kalrez is a registered trademark of Dupont Polymers, Inc.
Parofluor, Ultra are registered trademarks of Parker Hannifin Corporation
Perlast is a registered trademark of Precision Polymer Engineering Limited.
Teflon is a registered trademark of the Chemours Company
Vespel is a registered trademark of Dupont Polymers, Inc.
Viton is a registered trademark of the Chemours Company

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Material Family Guide

*Typical family ranges shown for quick reference only. Actual performance depends on compound, media, pressure, hardware, motion, and required life. Regulatory compliance is compound- and application-specific; availability of a compliant formulation should be confirmed for the exact material, hardness, configuration, and intended use.

Material Family	Typical Service Temperature*	Best For	Use Caution / Not Ideal For	Common Seal Formats
NBR / Buna-N	-40 to +250°F	Petroleum oils, fuels, hydraulics, and general industrial service	Ozone, weathering, UV exposure; verify modern fuel blends and aggressive chemicals by compound	O-rings, x-rings, custom molded shapes, gaskets
HNBR	-40 to +300°F	Hot oils, fuels, refrigerants, and higher-heat dynamic service	Verify fuel, sour-gas, chemical, and low-temperature requirements at the compound level	O-rings, hydraulic seals, custom profiles
EPDM	-60 to +250°F	Water, steam, glycol fluids, ozone, and outdoor service	Petroleum oils and hydrocarbon fuels; verify cure system for steam/hot-water service	O-rings, sanitary seals, gaskets, custom extrusions
VMQ / Silicone	-80 to +450°F	Very wide temperature exposure, food/medical options, static seals	Abrasion and tear resistance; validate dynamic service, oils, and repeated steam exposure	O-rings, gaskets, molded shapes
FVMQ / Fluorosilicone	-80 to +350°F	Low-temp fuel and oil resistance, aerospace/military environments	Higher wear/dynamic abuse than tougher elastomers	O-rings, specialty aerospace seals
FKM / Fluorocarbon	-20 to +400°F	Chemicals, fuels, oils, and high-temperature sealing	Prolonged steam/hot water, amines and ketones in many grades; specialty compounds may differ	O-rings, x-rings, gaskets, custom molded shapes
FFKM / Perfluoroelastomer	0 to +550°F	Extreme chemicals, high purity, plasma, high-cost downtime environments	Cost-sensitive applications	O-rings, specialty custom seals
PTFE	-300 to +500°F	Broad chemical resistance, low friction, non-stick surfaces	Elastic recovery; often best in spring-energized designs	Backup rings, spring-energized seals, machined seals
PTFE Encapsulated	Depends on core + jacket	Chemical resistance with elastomer-like geometry	Dynamic applications, tight bend radii, and some compression-set limitations	Encapsulated O-rings, D-rings, square rings
AFLAS / TFE-P	15 to +450°F	Sour gas, amines, steam, aggressive oil & gas media	Low-temperature service; verify aromatic/chlorinated solvent compatibility by compound	O-rings, engineered oil & gas seals
Polyurethane	-40 to +225°F	Abrasion resistance, extrusion resistance, and hydraulic sealing	High heat relative to FKM/FFKM; hydrolysis resistance varies by polyurethane chemistry	U-cups, rod seals, piston seals, custom profiles
Neoprene / CR	-40 to +250°F	Refrigeration, moderate weathering, general-purpose industrial service	Premium chemical/high-temp duty	O-rings, gaskets, molded shapes

FAQs

What is the best material for an O-ring?

There is no universal best material. Start with media, temperature, pressure, motion, gland design, and required approvals, then select and validate a specific compound. A sealing engineer can narrow the shortlist quickly once the application inputs are known.

Is FKM the same as Viton?

FKM is the ASTM polymer-family designation for fluorocarbon elastomers. Viton™ is a Chemours brand of FKM. Not every FKM compound is Viton, and FKM compounds within the family do not all perform the same: cure system, fluorine content, and formulation all affect properties.

Is EPDM compatible with oil?

EPDM is generally not recommended for petroleum oils or hydrocarbon fuels. It is typically selected for water, glycol fluids, ozone, outdoor service, and qualified hot-water or steam applications. If oil compatibility is also needed, a different elastomer family is required.

Can silicone be used in a dynamic seal application?

Silicone generally has poor tear and wear resistance relative to other elastomers. Dynamic use is possible under engineered conditions with the right compound, design, and lubrication, but it is an exception to validate, not a default. FKM or HNBR are more common choices for dynamic duty.

When should I specify FFKM?

Consider FFKM when the consequence of failure exceeds the material premium: aggressive chemistry, high purity requirements, plasma environments, or situations where downtime cost dominates. The specific grade still needs to be matched to the application; FFKM is not a uniform specification.

Can PTFE be used as a static gasket?

Yes. PTFE-based static gaskets are widely used. The design must account for creep relaxation, joint load, thermal cycling, and the specific PTFE form - filled, expanded, sheet, or spring-energized. Spring-energized seals are one solution for thermally cycled applications; they are not the only option.

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