Dear Kaushik Shandilya,

Thanks for your explanations. The values are in the same range I'm working with, for thermal expansion the pure PFTFE values I have so far are 50 per cent lower. For combination with silicate I'm using a value for the mixture, since silicate is about 2 orders of a magnitude lower.

Kind regards

Peter Woywode

Dear Peter Woywode,

I am not sure if it is still relevant but reading the answer above I could not help but notice that it is almost certainly an AI written answer, and it contains almost no information at all about the question asked.

As I also had some difficulties trying to find good information on the cryogenic properties of PTFE, I feel responsibility to share what I use, especially seeing this 2000 character GPT reply (I am sorry if indeed it was written by a human :) )

The documents I am using for reference are http://www.rjchase.com/ptfe_handbook.pdf and https://nvlpubs.nist.gov/nistpubs/jres/057/jresv57n2p91_A1b.pdf

The first is an extensive study on the material properties of Teflon, the second only talks about the thermal expansion, but as this was critical for me, I valued this second one rather highly.

Sadly, I am working with test setups at 4.2 K and I did not find any good reference material down to this temperature, but at the -200 C you mentioned, these two should be sufficient.

Hope I could help.

Good luck.

Kristof Brunner

Dear Kristof Brunner,

Many thanks for your answer and the Information you shared. The values for thermal expansion fit very good to the values I used in the temperature range -150 °C to - 200°C. Ther,al expansion coefficients was one parameters of a valve leakage analysis. We we solve the problem. The valve is running for 3 month with various fast temperature gradients without any leakage. All the best for you.

Kind regards

Peter Woywode