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.
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
- Hypalon® (chemically similar to neoprene.)
- 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.