I am currently working on an engineering project with a friend. Without giving too much away, I have two parallel strips of Zirconium-Copper alloy sandwiched between an upper and lower piece of smooth PTFE. Between those two strips of metal runs a channel, and I wish to run liquid nitrogen (or another cryogenic coolant) in there.

My question is will a pressure seal alone (light pressure being applied from top and bottom uniformly) be enough to keep the liquid nitrogen in the channel? Will PTFE seal when pressed against itself, or when pressed against a metal?

To be clear, this is oil-free PTFE without any filler.

Some data on the materials:

PTFE data sheet

Zirconium Copper Alloy

An image of the setup. PTFE is in white, copper in orange... This is just a crude representation.

enter image description here

  • 1
    $\begingroup$ PTFE forms an air tight seal against glass (J. Youngs valves), so i would assume it should be fine with smooth metal as well as long as your design is correct (the one in the pic doesnt seem great for forming a seal). However the issue here is that due to the liquid nitrogen PTFE will shrink and you will lose the seal (this even happens in the freezer) so i dont think the above setup is suitable for liquid nitrogen. If you share more info on what you are trying to do i might be able to help. $\endgroup$
    – AMM
    Mar 6 '18 at 11:34
  • $\begingroup$ Hi, thanks for the comment, this mostly answers my question. The image is really just a crude visual, in reality there are PTFE fasteners (nuts and bolts) going through both PTFE and copper, and tightening them together. My concern was that some materials really don't seal well, as well as some fluids really tend to go through the smallest gaps. But from what you commented, PTFE should have no issue forming a seal once the fasteners are in and tightened. I mostly wanted to avoid an additional gasket or sealant. $\endgroup$ Mar 6 '18 at 15:34
  • $\begingroup$ Actually, i should also have mentioned that there are PTFE swagelok ferrules and fasteners used to seal gases under pressure which is the best example of such use of PTFE as well. My only concern is that i dont think any of that will work well at very low temperatures. $\endgroup$
    – AMM
    Mar 6 '18 at 16:01

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