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Posted by Uncle Al on July 16, 2009, 12:12 pm
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Gas Bag wrote:
>
> Green
>
> Thanks for your reply…..and all the others. I’m well aware there are
> a whole variety of anti-fog liquids/gels/waxes available. In fact
> there’s a particular brand that I use for masks/goggles - it’s
> absolutely amazing, and I swear by it. (I’m more than happy to let
> you know, but I don’t want to seem like an advertisement for them)
> But what I’m trying to do is achieve a permanent effect that is 100%
> effective; there already is some technology out there that does
> exactly that. Take a look:
>
> http://www.abc.net.au/ra/innovations/stories/s1213247.htm
>
> As fogging on glass/plastic surfaces is caused by water’s surface
> tension, I thought perhaps a very slightly rough surface might help
> break the surface tension of the tiny water droplets. I’m guessing
> probably not, but there’s no harm in asking.
If it is a hydrated silicate surface you monolayer it with a reactive
silane, RSiX3. -X is typically -OMe or -Cl. R is typically a three
atom spacer then a quaternized ammonium with counterion. That
drastically reduces the surface tension and water sheets not fogs.
Presumably a PEO or poly(vinylpyrrolidinone) oligomer tail would also
the job.
Rain-X takes the opposite tack. Now R is a silicone oligomer and the
treated surface is hyperhydrophobic. Water violently beads but a
breeze blows it off. Very nice for windshields - your wipers glide
across the surface if you need them at all. After treatment, lightly
burnish the surface, wipe with rubbing alcohol, and burnish again.
That gets rid of most of the residual goo.
One wonders why competition swimmers don't "condition" their skin with
hydrophobes. Uncoupling the otherwise wetted surface would
substantially decrease friction.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/lajos.htm#a2
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