Plastics to tolerate -300F for liquid nitrogen generation

[imsmooth]

Maybe someone here will have an idea where I can get some information. I am planning on making liquid nitrogen from air and will need to regenerate waste gas. This gas will be very cold (-300F) and will get transported through some tubing system. Is anyone aware of any plastic tubing material that will tolerate these temperatures? Polycarbonate is the best I have found so far, but it is not good enough.

Otherwise, I will have to use metal tubing.

 

[imsmooth]

I'm thinking teflon tubing might work. Any thoughts?

 

[K^2]

If you need some plasticity, anything that won't turn brittle at these temperatures will be either liquid or extremely soft at room temperatures. Any basic materials you can find to work with will be extremely brittle at -300°F. I would bet on metals being more suitable than plastics, as they tend to have a better range of temperatures. There are some alloys that are designed for low temperatures that aren't prohibitively soft at room temperatures to be worked with.

 

[Andy Resnick]

Maybe someone here will have an idea where I can get some information. I am planning on making liquid nitrogen from air and will need to regenerate waste gas. This gas will be very cold (-300F) and will get transported through some tubing system. Is anyone aware of any plastic tubing material that will tolerate these temperatures? Polycarbonate is the best I have found so far, but it is not good enough.

Otherwise, I will have to use metal tubing.

Cryogenic delivery hoses are typically multilayer metal devices:

http://www.sigmasystems.com/accessories-tp/hoses/cryo-hoses.htm

The storage vials I use are made of polypropylene, but I think that material would be a poor choice for cryogenic tubing.

 

[f95toli]

Teflon should be ok. Just make sure you attach it to something so that it can't vibrate (which it will do if you pump LN2 through it) since this will cause it to eventually break. You will NOT be able to bend the tube once it is cold without breaking it, but I hope you've already realized that (If you want a bendable tube you need something metallic).
Also, use an armoured tube if you can find it. It will reduce the chance of the tube exploding. Note my choice of words, when an plastic tube at 77K bursts it does so in quite an spectacular fashion resulting it lots of small bits of plastic (I am speaking from experience here).
Note also that a tube can work really well for years and then suddenly fail, I would not recommend being too close to an uprotected tube (I've had a LN2 shower once when a tube burst, I don't recommend it).