ESL Diaphragm coating

[JonasKarud]

Yes.

[arend-jan]

Originally posted by JonasKarud
arend-jan, I can give it away, but we have to ask Capaciti for permission.

OK, I was under the impressions that it was your formula.

[SY]

Originally posted by JonasKarud
Sy, can a 15 kV corona charger from a copier be used?

I don't know, I haven't tried it. I would suspect that it's not strong enough, but it's worth trying if you've got one laying around. I would certainly allow a very minimum time between treatment and coating, i.e., coat as quickly as possible following treatment.

Measuring surface energy is a bit trickier. I use dyne solutions (basically dyed mixtures of two solvents in different proportions for different dyne levels); a bit of the solution is painted onto the surface and either wets or beads up. A qualitative way to examine surface energy is to carefully put a drop of water on the surface and look at the contact angle compared to the contact angle of an untreated surface.

[JonasKarud]

Maybe one should try to apply the coating and do the corona treatment while the coating still is wet, and maybe from beneath?

[SY]

No, that won't work for several reasons. You want to treat a clean, dry surface. This will allow the applied coating to wet the surface thoroughly and "bite in." Treating from the rear will only treat the rear- this is a surface effect, not a bulk one.

A good surface treatment will cause breakage of chemical bonds, formation of radicals, and some oxidation of the surface. The depth of this disruption is on the order of 100 angstroms.

[Capaciti]

Hi Jonas,

funny that you request my permission for open knowledge of YOUR !!! recipe.

I do not have any problem with it.

So feel free to announce your recipe

PS: I wondering about discussion of corona treatment. As coating will have adequate wetting, there is no need for corona treatment, i would even expect additional negative effects regarding performance under high humidity, since the rougher surface will attract more water molecules.

Capaciti

[SY]

This turns out not to be the case. Once the coating is applied, hydrophilicity is independent of the surface treatment. The coating takes up any of the roughness, since the roughness is on a sub nanometer scale and the coating thickness is on a micron scale.

[Few]

Thanks for the helpful comments, Sy. I hadn't caught the important point that a non-point source of the discharge is used.

Do you have any idea of whether a UV lamp might serve a similar purpose and whether the mylar would tolerate it? They both generate ozone, and I've used a UV lamp to clean surfaces in other contexts. The UV source might be cheaper/easier to rig up than a Tesla coil system for DIYers, but I think the ozone production might be lower.

I made a UV source by removing the glass shroud from a discharge lamp I bought at Home De(s)pot. It's not something that would receive OSHA's blessing, but it gets the job done for small samples in an enclosed space.

Few

[SY]

I played around with UV as a surface treatment about 15 years ago. It wasn't optimum, it took a LOT of intensity, and it tended to degrade the bulk. It heated the substrate like crazy, too. I've also used open plasma systems (from Electro in St. Louis), but besides being big and expensive, they only worked intermittently- the planets apparently had to be in alignment...

Blown arc/plasma is still the very best way, but that's not a diy-friendly procedure! The best one I tried was from Arcojet.

[bolserst]

Originally posted by Few
Sy,
How is a point source of high voltage used to treat uniformly a large surface such as an ESL diaphragm? Do you just wave the Tesla coil in the vicinity of the diaphragm and let it choose where the arc is directed? Sorry if I'm missing something that's supposed to be obvious...
Few

You might take a look at US Patent 4693869 to get an idea what electrode geometry might work well for attaching to a tesla coil for surface treatment.

http://www.google.com/patents?id=S2w...ad=0_0#PPA1,M1