> I'm looking for a varnish/paint/conformal coating that has 
> good UV
> durability and low water absorption. This is for an 
> outdoor use, and
> it's capacitive sensor so I need to keep the thickness 
> down, so using
> glass or even tape would cut down on the performance.


Consider the  Dow corning "Silicone Rubber" conformal 
coatings.
A good range with a cross section of different properties. 
UV performance no doubt varies amongst products but SR as of 
right tends to have better UV performance than eg epoxies 
due to the higher bond energies than C-C products.

As an example Dow Corning 1-2620 Low VOC RTV coating may 
suit. This is a thinner version of 1-2577 but gives the same 
end result. Coatings of under 0.1mm are possible depending 
on application method and initial thinning. (I'm using 
1-2577 experimentally but only because it was what I could 
get fastest when I needed it. I'd possibly have gone for the 
low VOC or 1-2620 if I'd had more time). Not cheap but 
applies thin enough that cost/unit will not be vast. 
2620/2577 have the bonus (if you need it) of being 
'transparent enough' for eg solar cell use.

A number of Dow Corning products have standard and low-VOC 
versions and the latter are liable to be better on your 
health as they lack the volatile organic solvents of the 
standard products.

Chapter and quite a few verses on quite a lot of their range 
here

        http://www1.dowcorning.com/DataFiles/090007c88017e83f.pdf


        Russell



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