chloride diffusion in ptfe vs eptfe 1

[keller529]

anyone have first hand experience in this area? specifically does chloride diffusion present an issue in ptfe vs eptfe? (thinking gaskets here) eptfe is much more porous, but in a gaske thats compressed, how much an issue is this?

i need a brain dump on the topic. tia

 

[shvet]

1/ Chloride or chlorine? If chloride - a brine, or a gas, or whatever?
2/ What do you mean "diffusion"? Fluid leaks? Gaskets permeability? Gasket swelling or degradation?

What are you concerned in? What issue are you talking about? A gasket is porous - and what?

 

[pierreick]

Hi,
Consider the link underneath, you may want to contact those guys.

https://www.nbseals.com/what-is-the-characteristic-and-application-of-expanded-ptfe-gasket/

Pierre

 

[TiCl4]

I think OP means chlorine gas, which can indeed permeate through PTFE material. The mechanism by which this occurs is periodic substitution of a F with a Cl on the polymer chain. Though F affinity is higher, it can be substituted by a Cl. Since F affinity is higher, it will return to kick the Cl off, which then travels along and substitutes another F on the chain. Overall, this allows Cl2 to eventually diffuse through a solid PTFE membrane. You can read more about this at the link below.

Note the following statement at the end: The results obtained are, on the whole, extremely variable, and owe much to the method of fabrication of the test membrane, and the exact test methodology used. Attempts to translate this thin film data into meaningful data for liners used in piping systems (with liners typically ranging from 3 – 10mm thick) have proved to be singularly unsuccessful.

Permeation of PTFE

Learn about the permeation of PTFE at PTFE Applied Coatings. Discover factors affecting permeation and ensure optimal performance for Teflon® and Xylan® coatings.

fluoroprecision.co.uk

 

[EdStainless]

Chlorides (and other ions) will permeate through PTFE and other fluoropolymers.
We used some 'teflon' (various grades) insulated wire and after long term exposure we could measure the leakage current through the insulation.
On the microscopic level these materials are porous.