On 9 Jul 2002, at 21:43, John Carmack wrote:
>
> This was an all stainless steel and Teflon check valve, but the Teflon had
> gotten rather hard and crumbly, and eventually fallen apart. This was one
> of our very early purchases, so it had been exposed to peroxide over a year
> ago, and may have been slowly deteriorating since then, even though it
> hasn't been in peroxide flow service with much of any regularity at all.
> Mark Henry (ex Beal propulsion engineer) had mentioned to us once that not
> all Teflon is completely peroxide compatible, and this seems to be an
> example of that. Unfortunately, industrial suppliers don't make a
> distinction.
>
According to EI Dupont de Nemours
http://www.dupont.com/teflon/coatings/basic_types.html
there are six basic types. Regarding their inert properties, Dupont says
they are all wonderful. "Extremely resistant to chemical attack", or
some such phrase of art.
Better information on Teflon properties was at
http://www.omega.com/techref/fluoro.html
and at
http://www.boedeker.com/ptfe_p.htm
Unfortunately, I found no mention of compatibility with HTP on either.
The Cole-Parmer chemical compatibility database, at
http://www.coleparmer.com/techinfo/chemcomp.asp
rates PTFE Teflon as "Excellent" in compatibility with 100% HTP. That's
something, at least.
The "O-ring chemical compatibility guide" by Engineering Fundamentals,
at
http://www.efunda.com/DesignStandards/oring/oring_chemical.cfm?SC=n
one&SM=Teflon%2C%20Virgin
says "0" (no data) on virgin teflon with hydrogen peroxide.
You'll want to read these two
http://www.ee.surrey.ac.uk/SSC/H2O2CONF/afrolov.htm
http://www.ee.surrey.ac.uk/SSC/H2O2CONF/feigenbaum.htm
just for general reference -- assuming you haven't already.
Chris
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