FEP is even better (Fluorinated Ethylene-Propylene copolymer). It's
just about as water repellant as PTFE, but it's a thermoplastic, and so
the optical quality of thin films of it is much better than those of
PTFE. It's obtainable in sheets down to 25 um thick. Goodfellow charge
an arm and a leg, but I have bought some gift-wrap, not outrageously
expensive, which appears to be FEP and is 40 um thick.
Chapter and verse, please.
I would rather trust
The PTFE we know and love, polytetrafluoroethene with no hydrogen in
its composition at all and little main-chain branching, is not a
thermoplastic. Blocks of PTFE are formed by sintering the powder at
temperatures close to the decomposition temperature. That's why PTFE is
never transparent. I don't quite understand how they manage to make it
in 10-um thin sheets, but even that is translucent rather than
transparent, it is full of microcracks and cavities, and its mechanical
properties are not brilliant.
Well, Wikipedia backs you up. I had thought that a thermoplastic had to
melt outright. They have gone and changed the definition while my back
was turned. Well, FEP does melt before it decomposes, and thin films of
it have better optical and mechanical properties than PTFE as a result.
Silicone spray, there are a couple different types. Polydimethylsiloxane
will not form a dry film by itself. But you can get spray-on stuff that will
form a dry film, probably from www.mcmastercarr.com or
www.freemansupply.com and I think that these guys also carry it
Treating a substrate to polydimethylsiloxane fluid would probably work
temporarily. It's just silicone spray on lube, but wont form a dry film.
It all depends on your substrate.
Dissolving some parrafin in fuel oil makes a great release agent for
concrete and the parrafin is extremely hydrophobic. But soy wax is vary
slightly water soluble.
For glass silicone spray rubbed dry works very well to make
glass shed water and dust both. Every day when we started up and
just before sundown if we were working at night and we did most
nights we would clean all the glass squeaky clean a spray on
silicone and rub it dry with paper towels and for at least 4 or
5 hours if dust stuck to the windows you could hit and it would
fall off. If it got real dry add a rub down with fabric softener
before the silicone to help dissipate the static charge.
Could you give us some details on the application? Do you require a
coating or a separate sheet/film? Do you want the material in bulk?
If you're only interested in a coating with water-repellant properties,
RAIN-X or another automotive wax would work just fine, as long as it
could adhere to your substrate.
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