PEEK in Cryogenic service

[iainuts]

I'm looking for info/advice on the use of PEEK in cryogenic service. I'm considering the use of 30% carbon fiber filled PEEK (no lubricants or additives such as Teflon) for components that will be under considerable stress at cryogenic temperatures, down to -452. I've done some research and found that this material has been used at low temps. One issue is stress (parts will be stressed to roughly 10,000 psi in bending) and the stress will be cyclical, ie: the part will be subjected to tens of millions of cycles, so fatigue is an issue. Stress will be from 0 to 10,000 psi, and back to 0, not completely reversing. This is worst case, and most stress will be significantly lower. Note the bending strength of this material is roughly 25 ksi.
1. Is there a fatigue limit for this material? Is there a limit at this temperature?
2. Should I be worried about annealing heavily machined parts? I see this is a recommendation from the material supplier. Does anyone have any experience with using this material without annealing?
3. Does anyone have data on physical properties for this material at this temperature?

Thanks in advance for any help you can offer.
Dave.

 

[unclesyd]

Check out the two following websites

http://www.gtweed.com/FluidHandling/fharlonproducts.htm

http://www.victrex.com/

 

[iainuts]

Thanks,
Dave.