I make a thermal actuator that works with the expansion of diethyl ether at its boiling point of around 34 °C. For sealing and lubrication of the polypropylene piston and barrel, I need a lubricant that is immiscible with diethyl ether and does not react with it.

I found that diethyl ether is slightly soluble in water, and that it dissolves oils. I suppose this means that many of the everyday oil- and water-based lubricants are not fit for this application (as diethyl ether will dissolve in the lubricant)?

Any other suggestions for a lubricant that can be used here?

  • $\begingroup$ Let me ask: can't you consider another liquid with low boiling point, other than ether? Diethyl ether is a great solvent, and anything that comes to my mind (oils, silicone, etc) are soluble in it. $\endgroup$ – The_Vinz Jul 18 '19 at 23:07
  • $\begingroup$ Thanks. An alternative would be N-pentane (boiling point 36 °C), which apparently is insoluble in water, but which is a little bit harder to obtain. Would it be possible to super-saturate a water-based lubricant to minimize dissolution of diethyl ether in it? $\endgroup$ – J. Bowden Jul 19 '19 at 16:56
  • $\begingroup$ Solid lubricants, such as graphite and molybdenum disulfide might reduce friction, and are not soluble, but might not help sealing... you'd need to test. $\endgroup$ – DrMoishe Pippik Jul 21 '19 at 4:56

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