May 2017

Gasket Material Compatibility Chart for Chemicals

May 22, 2017

Selecting the right material for a gasket is never easy. Temperature and pressure must be considered, and so too must the nature of the fluid being sealed. Some combinations of fluid and gasket material are just incompatible. Choose wrongly and the gasket will fail prematurely. When purchasing gasket material, mention the intended purpose. That way a material specialist can tell you if there’s a better alternative.  View our rubber sheet gasket material compatibility chart for chemicals.

Learning More About Material Compatibility

Some of the most frequently used gasket materials are neoprene, nitrile rubber, EPDM, silicone and Viton®. (Technically, this last one is a DuPont tradename for fluoroelastomer or FKM as it’s known in the ASTM standards.) Each has strengths and weaknesses in terms of chemical compatibility. “Rubber Gaskets & Seals” on our website provides a summary of what chemicals various gasket materials do and do not work with.

The other way to approach material selection is from the perspective of the chemical. Unfortunately that means identifying every possible chemical, which makes for a very long list. For some commonly used fluids the lists below highlight good and bad combinations. But don’t rely solely on these – always ask advice!

Good Material Compatibility Pairings for Chemicals

  • Acetone (a form of ketone): EPDM
  • Aldehydes (found in many food ingredients): SBR
  • Ammonia: Good choices are neoprene and EDPM gasket material
  • Animal fats: Nitrile, Viton®
  • Automatic transmission fluid: Nitrile rubber (NBR) and Viton®
  • Brake fluid: EPDM and styrene-butadiene rubber (SBR)
  • Ethylene glycol (antifreeze): nitrile rubber, Viton®, EPDM and neoprene work well
  • Fuels and oils: Nitrile rubber (NBR), Viton®
  • Ozone: EPDM, silicone, Viton®

Bad Gasket Material Pairings for Chemicals

  • Acetone (a form of ketone): Avoid contact with nitrile rubber, neoprene, silicone and Viton®
  • Aldehydes (found in many food ingredients): Nitrile
  • Ammonia: Poor with SBR and Viton®
  • Animal fats: SBR
  • Automatic transmission fluid: Avoid EPDM, SBR and Silicone
  • Brake fluid: Viton®
  • Fuels and oils: EPDM, SBR, Silicone
  • Ozone: Nitrile and SBR

Seek Advice for Material Compatibility with Chemicals

These lists give only a superficial overview of a complex subject. The only sure way of selecting the correct gasket material for any given chemical is to seek guidance from a material specialist. At Hennig Gasket, if we don’t know we’ll find out.  Contact us Today.

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Gaskets for Low Temperature Applications

May 08, 2017

A common mistake when selecting gasket material is to consider only the upper temperature limit. Excessive temperatures can lead to gasket failure, but so too can low temperatures. The Challenger Space Shuttle disaster is perhaps the best known example of this.  Low temperature elastomers are worth looking at.

Gradual Transition

Metals are either solid or liquid with no fuzzy middle ground. Elastomeric materials like neoprene and SBR don’t have this clear melting/freezing point. They just become harder or softer. The dividing line is called the Glass Transition Temperature (Tg), but the difference in material behavior either side can be quite subtle. This makes it difficult for manufacturers of gasket materials to specify strict minimum temperatures. Instead, you’re more likely to see a range.

Elastomers and Low Temperatures

Low temperatures are a problem for elastomeric gasket materials, for two reasons:

  1. The lower the temperature the more the elastomer resists deformation under load. That’s bad because the material needs to squash into the faces being sealed.
  2. Low temperatures change compression set performance. A cold gasket material can take on a compression set and then leak as temperatures rise. (This is essentially what happened with the Challenger.)

Defining “Low”

In gasket terms, low temperatures are those which might be reached during winter in the upper Midwest. That means -20° to -40°F, which is far above the kind of cryogenic temperatures seen when processing and storing liquefied gases.

Gasket Material Selection

For very low temperatures, those down to -300°F, PTFE/Teflon gaskets are usually the material of choice. However, Teflon does tend to creep, making it unsuitable for some applications.

Silicone gaskets stay flexible at temperatures down to -80°F with some grades reaching -100°F. Nitrile rubber gaskets will typically work down to -80°F, although it’s important to check the material specs for details. Other elastomers harden before getting that cold, so always check material specifications.

Consider Both Temperature Extremes

Low temperatures can be as much of a problem for gasket materials as high temperatures. The loss of the Challenger serves as a reminder that gaskets may be exposed to temperatures below design limits.

Contact Hennig Gasket & Seals for your low temperature elastomer needs.

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