Would anybody know the following or be able to point me to a web resource?
Thanks
Do you know of any materials that retain some elasticity at cryogenic temperatures in the 20 degrees Kelvin range?
This would be for a bladder that would hold liquid nitrogen in a bath of liquid Hydrogen or helium under pressure. The bladder could either stretch or fold. So it does not necessarily need to stretch, just not crack while it was folded.
mgb_phys
Sep18-08, 03:01 PM
The only thing I can think of is a stainless steel bellows tube.
How much capacity/change in capacity do you need?
ccarleton
Sep18-08, 03:15 PM
Ideally the bladder would need to collapse completely.
Could there be any type of Silicon, plastic or rubber compound that might work?
mgb_phys
Sep18-08, 05:34 PM
Could there be any type of Silicon, plastic or rubber compound that might work?
It's a bit lower than I have direct experience of, but I doubt there are any plastics/rubber that are that flexible at 20K.
hypatia
Sep18-08, 06:03 PM
Polytetrafluoroethylene retains some plasticity at 20k.
Q_Goest
Sep18-08, 07:35 PM
Nitrogen will solidify at -340 F (aprox) regardless of pressure, so in a bath of LH2, you have other issues. At liquid helium temperature, even hydrogen is a solid.
Teflon will get hard, though if it's thin enough (ie: a few micron) it might work.
I'd suggest trying Kapton film, especially the reinforced variety that has fibers interwoven. Don't know what the fibers are made of though. I've experimented with Kapton film by dunking in liquid nitrogen, and it holds up surprisingly well. If it krinkles up, it will develop holes at the points where 2 folds come together. The key to retaining flexibility with Kapton (and most materials in this circumstance) is to get them as thin as possible to minimize bending stresses.
I've also tried various plastics including nylon, all of which failed miserably.
If you can explain your intented use, it would help.