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Old 17th November 2007, 09:28 PM   #31
SY is offline SY  United States
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Quote:
I received a funny answer mentioning some 'bi-activated' mechanism of course this means nothing. (bi what?, activated what?) They didn't explain. Yes, the price of their coating is surely bi or tri or giga activated. 59 euro for 20 cc !!!!!!!!!!!
Agreed, pretty suspicious. I've done a fair amount of work for the past 30 years or so on conductive coatings and ICPs (have a dozen or so patents on them, quite a few published papers, and run programs for top aerospace companies), and these are terms I've never heard of.

A decent coating can be made very inexpensively, but as I've said again and again and again (seemingly to no effect), the coating is no trick, it's the surface preparation of the film which is the key.
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Old 18th November 2007, 06:45 AM   #32
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Originally posted by SY


A decent coating can be made very inexpensively, but as I've said again and again and again (seemingly to no effect), the coating is no trick, it's the surface preparation of the film which is the key.
Chemicals can do the job as well (not always ofcourse).
Surface preparation is not that practical as the effect decreases with time. It also breaks covalent bondings of the surface.
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Old 18th November 2007, 11:04 AM   #33
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The treatment only needs to last as long as it takes you to paint the surface and dry it. That's pretty much a non-issue. Yes, it breaks covalent bonds (there aren't any other kinds in plastic film) on the surface- that's the whole point of it.

Chemical treatments can work, but the only effective ones are HIGHLY dangerous and toxic, so I won't make any recommendations.
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Old 18th November 2007, 01:15 PM   #34
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Originally posted by SY
The treatment only needs to last as long as it takes you to paint the surface and dry it. That's pretty much a non-issue. Yes, it breaks covalent bonds (there aren't any other kinds in plastic film) on the surface- that's the whole point of it.

Chemical treatments can work, but the only effective ones are HIGHLY dangerous and toxic, so I won't make any recommendations.

There is a whole world of modern glue and paint technology without using pretreatment, it is not a must. These paints and glues are not awfully toxic. No you can't eat or drink them but they won't burn off your skin.

I received a lot of feedback from DIY of all kind of products with their problems and their +. Adhesion problems are rarely mentioned as a problem, except in case of metalised Myar which is obsolete now anyway.
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Old 18th November 2007, 03:55 PM   #35
gvy is offline gvy  Belgium
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Hi,

I have been using a waterbased schoolglue from Velpon (without solvents) for some time now.
I spray it on in some layers with an airbrushpistol.

The good thing is that it sticks excellent to the mylar and holds for years, without any problem as I have experienced.
I can only clean it of the membrane , if I should want to, rubbing it with pure ammonia .
It is completely clear an feels dry and not sticky, ones dried out

The bad thing is that it's working as a conductive coating is based on the hygroscopic principle and so it's surfance resistance can get to high ,depending on weather conditions, also as I have experienced.
Anyway I want to have the surface resistance around 1Gohm, without changing to 20 or more Gohms.

I have been thinking if it could be an idea to mix a conductive substance (graphite based or other) with this glue, to get a substance that sticks well ( should not be a problem because this glue simply works) but also becomes better conductive and less dependant from air humidity (self conductive)

Any chemist who can help or give some tips?
I am shure willing to do some tests , measure, and publish here.
I use a Megger for high tension purposes to measure the surface resistance.

Geert
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Old 19th November 2007, 10:58 AM   #36
Calvin is offline Calvin  Germany
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Hi,

@Nevod
I wouldn“t regard the charge on the diaphragm as capacitor.
But if so Teflon would be the wrong conclusion.
Teflon is not stable against Ozone (which is nearly always created in an ESL in small doses).
Its dielectrectic constant is very low and its resistance values extremely high.
It is nearly impossible to get something to stick to Teflon, especially not a flexible and vibrating material.

A solution could be to use 2 very thin diaphragms of Mylar/Hostaphan and the coating between (as kind of a glue to both membranes)
This could reduce the problems of hygroscopic coatings and ageing and would even raise the flashover treshold a bit (~100-300V).

The waterbased glue, doped with ink (which works stable for Years now) is probabely the ideal DIY-option, since its cheap, easy to handle (brush, paint or spray), absolutely non-toxic, very thin and light and the parameters can be easily taylored to Your needs (a charging time of a few seconds is ok, 5min way too much).

As I am told(!) Gold as well as some other metallic compounds seem to be not stable in this application. Kind of “cracks“ seem to develop over time and under HV-conditions leading to a creation of little “isles“ of coating that loose more and more contact to each other till the coating fails to conduct. Same seems to apply to the ITO-coatings (which afaik ML used for a while). ITO coatings come as standard off the role 12µm thick material for TFT-displays is quite low in resistivity and could only be useful for smaller hybrid ESL panels.

jauu
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Old 19th November 2007, 12:05 PM   #37
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teflon is stable against ozone very well. Only fluor atoms on a carbon chain. The inertness of teflon makes it a popular meterial for chemist, think of all kind of rings, fittings, etc.
Adhesion is aproblem indeed as it is highly hydrophobic.
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Old 19th November 2007, 02:38 PM   #38
gvy is offline gvy  Belgium
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Hi Calvin,

What kind of ink do you use to dope the glue? and in which quantities.
Did you measure the surface resistance?

This weekend I coated a membrane with a mixture of waterbased glue and black waterbased airbrushpaint.
Once dry,te surface resistance measured around 4Gohm.
The recoated ESL is playing perfectly, but I really would like to find a way to get the surface resistance to around 500Mohm - 1,5 Gohm


The bizar thing is that in the past ( years ago) I measured resistances around 1,5Gohm... with a mixture of that shoolglue with some drops of blue airbrushink.

I wonder if mixing the glue with graphite particles or for example with contact chemie graphit33 could work?
Or is there another waterbased well conducting liquid, wich can be mixed with te glue?

Another thing.
Has anyone on the forum ever tried Contact chemie antistatic 100.
I think it may be a bit to good conducting and I don't know how it will stick on a moving membrane in time?

Geert
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Old 19th November 2007, 02:51 PM   #39
SY is offline SY  United States
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Graphite is not an optimal material to use for loading a high resistivity coating. A high structure carbon black would be a better choice.
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Old 19th November 2007, 03:32 PM   #40
gvy is offline gvy  Belgium
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Quote:
Originally posted by SY
Graphite is not an optimal material to use for loading a high resistivity coating. A high structure carbon black would be a better choice.

OK,

And where or in what produkt do I find it? ( that can be mixed with te glue as adhesive)

Geert
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