I have an electrochemical cell which houses solutions via PEEK material and seals with a couple O-rings. For many solutions the Viton O-rings I've been using work just fine, but for some solutions (particularly those containing Grignard reagants) the O-rings are not compatible and will swell and even degrade relatively quickly. Can anyone suggest the best O-ring material for use with chemicals such as these?
McMaster-Carr offers an O-ring made from Kalrez compound 4079 that they say "resists nearly all classes of chemicals except some fluorinated solvents." As of right now, this looks like my best bet. It's pretty expensive for an O-ring though. $45.17 per O-ring for the size I need! There are also hard PTFE O-rings but they are likely to hard for my application.
Teflon seals have worked well for me. If you need softer and more flexible O-rings, then you might consider fluorosilicone O-rings.
Fluorosilicones seals will likely provide you with the flexibility and chemical resistance that you are looking for.
Good afternoon, Tylan.
Some variables must be considered when specifying sealing materials. In addition to this chemical agent should consider temperatura, pressure, if the application is dynamic or static among other factors. Have you tried expanded PTFE? Can you provide more information?
The application is dynamic and done at room temperature and roughly 1atm pressure. I would describe the electrochemical cell as being similar to a coin cell but bigger, with a larger volume of solution, and can be reassembled. The O-rings do the sealing so are in contact with whatever solution I use. The chemicals I am having issues with are Grignard Reagents which are nucleophilic Lewis bases so must be attacking the Viton O-ring material in some way. I just received a few Kalrez Perfluoroelastomer O-rings from McMaster-Carr and am going to use them today. They are supposed to be a lot like the PTFE material, but maybe more flexible? I will follow up on whether or not I think these are working well.
Good morning.
Thanks for the information. I hope you have success with the Kalrez. If this does not occur and you find it convenient to send me the picture or the image of the place to be sealed. This way, I can assess if there is any way commercial or not to improve the sealing of the system.
The Kalrez Perfluoroelastomer O-rings appear to be working quite well. They were used in an overnight experiment and show no signs of degradation.
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