September 2017

Ketones and Gasket Materials

When selecting gasket material it’s important to look at the media being sealed. Some gaskets will not work with some chemicals. One example is the group known as ketones. Many gasket materials are not recommended for sealing these. If the product you are sealing contains ketones it’s important to know which gasket materials will work. Unless you’re a chemist it may not be obvious when a fluid contains or incorporates ketones. Here we’ll explain briefly how to recognize ketones and discuss which gasket materials to consider.

Ketone recognition

To chemists ketones, and the closely-related aldehydes, are a family of organic compounds containing a carbon-oxygen grouping. Products composed of ketones can sometimes be recognized by their name. The solvent acetone for example, is a ketone, as indicated by the suffix, “one.” Likewise, the term, “aldehyde” appears in many chemicals, such as formaldehyde.

As organic compounds, ketones and aldehydes occur frequently in nature and are generally liquid at room temperature. Examples include extracts of cinnamon bark, vanilla bean, lemongrass and the coriander herb. In addition, many fragrances gain their distinctive odor from various aldehydes.

In short, many food preparation processes, especially in baked goods manufacture, expose gaskets to ketones, as do a range of perfume and solvent processes.

Gasket materials susceptible to ketone attack

A long list of commonly used gasket materials are attacked by ketones and aldehydes. This includes:

  • Nitrile rubber/NBR/Buna-N
  • Neoprene
  • Hypalon® (chemically similar to neoprene.)
  • Silicon
  • Fluoro-silicones
  • Viton and other fluor-elsatomers

Gasket materials with some ketone resistance

Three materials stand out:

  • Natural rubber (rarely used due to its inconsistency and poor temperature properties.)
  • SBR/styrene butadiene rubber (not resistant to methyl ethyl ketone)
  • EPDM (not resistant to methyl ethyl ketone)

Consider the media

When selecting gasket material it’s essential to consider the media being sealed. Chemical incompatibility will lead to the breakdown of the gasket material and failure of the seal. Ketones, and their related organic compounds, aldehydes, present particular challenges because they occur widely and few materials offer good resistance. If ketone exposure is possible SBR and EPDM gasket materials should be your first choice.

How Low Can it Go?

Low temperatures play havoc with elastomeric gasket materials, as NASA will testify. (Details of how seal failure caused the Challenger disaster are available on the NASA website.) The issue is that at low temperatures gasket materials like nitrile rubber and neoprene become stiffer and less able to fill gaps. The TR10 number, derived from ASTM D1392, shows the temperature at which this stiffening affects sealing performance. The problem for problem for people buying gasket material is knowing how low temperatures can go.

Global lows

Military Standard MIL_HDBK_310_1851 “Global Climatic Data For Developing Military Products”, tells equipment developers what conditions to design for. This notes that the lowest temperature ever recorded is -68°C (-90°F), in the USSR. Statistically, the lowest temperature to be expected in the coldest regions of the world is -69°C (-92°F).

Low temperatures in the USA tells us the lowest temperature experienced in the U.S. is -62°C (-80°F), in Prospect Creek Alaska. Closer to home, the lowest in the contiguous 48 is -57°C (-70°F), measured at Rogers Pass, Montana. For those in the Midwest, record lows in Illinois, Indiana and Ohio are in the -34°C (-30°F) range, while Michigan, Wisconsin and Iowa have records ranging from -43°C to -48°C (-45°F to -55°F).

Of course, this is without the effects of wind chill. Air flowing over surfaces takes heat away, making the temperature appear lower than it actually is. And the harder the wind blows, the greater the cooling effect.

Implications for gasket material selection

When selecting gasket material for outdoor applications it’s essential to determine the lowest possible temperature. Not doing so risks leaks during periods of extreme cold, which is never a good time to be replacing a failed gasket!

Most nitrile rubber, EPDM and neoprene gasket materials work down to around -46°C (-50°F). HNBR is limited to around -40°C (-40°F) while silicone will endure temperatures down to around -59°C (-75°F). (values vary for individual material grades.)

If a gasket might be exposed to low temperatures material should be selected to suit. Specialists at Hennig Gasket will be happy to advise.