HNBR & FFKM Elastomers: When Standard Rubber Isn’t Enough

When NBR or FKM starts failing—under sour gas, high dynamic load, or the most aggressive chemicals—engineers step up to HNBR and FFKM. These specialty elastomers extend service limits dramatically, but at a cost that must be justified. This guide explains when to specify them, how they compare, and where they are used, with links to our rubber seals and custom rubber parts pages.

HNBR (Hydrogenated NBR)

HNBR is NBR with saturated backbone—dramatically better heat, ozone, and oil resistance, plus excellent dynamic and abrasion properties. It is the workhorse of automotive timing belts, oil-field packers, and aggressive-fuel seals.

• Temperature: roughly -40°C to +150°C (some grades higher).
• Strengths: sour-gas (H₂S) resistance, high tensile, good abrasion.
• Uses: oil & gas, automotive, power transmission.

FFKM (Perfluoroelastomer)

FFKM is essentially PTFE’s elasticity: near-universal chemical resistance and the highest temperature ceiling of any rubber. It is the last resort when nothing else survives the media.

• Temperature: up to ~+315°C continuous in some grades.
• Strengths: resists acids, solvents, plasmas, and oxidizers.
• Uses: semiconductor, chemical processing, severe oil & gas.

Aflas (TFE/P)

Aflas is a tetrafluoroethylene/propylene copolymer strong in steam, acids, and amines—often a cost-effective alternative to FFKM where extreme temperature is not required.

Comparison

See also our FKM vs Viton vs FPM and FFKM/FKM/Aflas for oil & gas articles.

How to Decide

1. If media is oil/fuel at moderate heat: NBR or FKM.
2. If sour gas or high dynamic load: choose HNBR.
3. If the chemical list includes strong acids/solvents/plasma: step to FFKM (or Aflas for steam/amines).
4. Justify FFKM only where FKM/HNBR genuinely fail—it is premium-priced.

For standards, see NACE MR0175 / API 6A.

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