High strength Dielectric Coatings, fact or fiction

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I just found a site that said Shelac only has a 200V per mil break down factor.
I thought is was much higher than this.
Polyurathene or acyrlic is up into atleast the 400V to 500V per mil range or better.
I will research this more and let you know what I find.

I do know that shelac does have higher dielectric constant though but not so much higher to warrant it's use for a large panel.
But it may work very well for head phone drivers though.

jer :)

P.S. Actually it is not quite bad at all !

http://www.shellacepc.com/properties.html
 
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Here is a great list of Material properties,

Boedeker Plastics : Material Selection Guide

According to this list Kynar is 1700V/mil, WoW !!
This confirms my testing of this material.
With a Dielectric constant of 8.5.
This looks very inviting for those whom like to use the wire method of building stators !
Hmmm.............


I have been wanting to try Kynar covered wire wrap wire and this might justify the cost of its use.
1700V/mil is the highest I have ever seen for a wire.
The last time I had searched for magnet wire or wire in general,I don't think that I have found this type of rating at all.

jer :)
 
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According to this list Kynar is 1700V/mil, WoW !!
This confirms my testing of this material.
With a Dielectric constant of 8.5.
This looks very inviting for those whom like to use the wire method of building stators !

Yup, on paper Kynar has always looked to be a step above PVC for ESL stator insulation in terms of dielectric constant and bulk resistivity. As far as the 1700V/mil...remember the insulation thickness on most Kynar insulated wire is 5mil. Most PVC wire has 15mil thick inulation. With PVC having a dielectric strength of about 550V/mil, the overall dielectric strength of Kynar insulated wire is essentially the same as for PVC insulated wire.
 
Yes,I am trying to find it on some Steel wire like copper plated TIG wire or something.
This way they could be self/semi supporting and/or not as fragile.

I have seen tube material available but this is still a bit costly.

Cost factor is my main goal when I do my researches as you can't go wrong with the technology no matter what form of construction you use.

jer :)
 
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James, At no time did I mention Shelac, I did however mentioned that I tested a piece of brass coated with primer, paint and then Polyurethane.

In my controlled test, essentially full insulation of the material using 1 coat of primer, 1 coat of black polyurethane and 4 coats of clear polyurethane. This provide the resistant coating of just under 3kv bias voltage.


Doc
 
sorry must have been in another active thread where Shelac was mentioned. A white primer as a base coat may well provide some de stressing to the overall coating as the oxides will be conductive enough to let the charge move over a larger area rather than build up in one spot. This technique is employed in high voltage cable designs for the same reason. Hope this is of interest best regards Moray James.
 
Yes,I believe we had touched on that before.
The aluminium screen stator material that I do have almost ready has a base coat of a acid based zinc primer and then a coat of black enamel, then a few coats of primer that has a talc filler and is now ready for a heavy coat of 2X clear.

I am waiting to get my Variable HV Supply done first, so that I can check what I have done so far.

jer :)
 
Hi,

Kynar is really interesting stuff, regarding its electrical parameters.
It may have its issues with glueing to a stiffening structure.
The wirewrap wire is also easy to source and it is intended to be ´pulled´ in small turns. It should not give problems whem stretching the stator structure taught and plain.
But best is..... the wire is silver-coated copper!
Now if that isn´t HighEnd :D

jauu
Calvin
 
FWIW, Glyptal is cellulose nitrate based; with acetone or ethanol carrier. Long term stability is an issue, but it's soluble in the original carrier, so can be removed or re-applied.

Shellac has more serious long term stability, and cross-links over time making it difficult to remove.

" ...
I have had Krylon's engineers find out for me if their conformal coating is the same as their clear acrylic enamel spray and the conclusion was that it appears to be but he could not give me a straight answer as yes or no.
..."

I would read that to mean "it is the same but company policy is I can't say that out loud because like all paint companies, we're very protective of our exact formulations because our competitors want to know that info".

In general, the ingredients used to make paint are well known but the proportions in each individual product are not and fall under the category of trade secrets.

Note also that when you look at a can of paint, the manufacturer is required to list all ingredients but is allowed to jumble the order, so it's not in proportion from most to least, like a food label is. The MSDS might give clues as to the formula because certain %'s trigger different regulatory categories, so they have to mention that sometimes.

It also may be possible to learn things from checking product information, including health & safety data, from different nations since the regulatory requirements might vary, offering other clues (one of the not-so-often mentioned reasons behind a push for harmonized regulations worldwide).
 
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Thank James for the information, actually it is very interesting! I'm however just looking for the Holy Grail for High dielectric coatings. Did you ever review the CRC's product which claims a 3kv/mil coating spray?

I keep hearing Jer's caution of products claims...LOL

I'd like to hear your opinion...to me, it chemically looks very much like every other vanilla flavored Polyurethane.......

https://images.tradeservice.com/gjPilrcyNvvpVtln/ATTACHMENTS/DIR100017/CRCINDE00027_1.pdf

Regards,
Jerry
 
JooJoo1234, What are you talking about???

Rust, in short is Iron oxidation from moisture and Oxygen (Fe2O3·nH2O, and (FeO(OH), Fe(OH)3) , rust has nothing to do with this thread.

Where are you getting those dielectric ratings from, Which brands are you referring to, what colors are you specifically speaking of??

With all due respect, you may want to read the thread prior to commenting on it.
 
Well, first. I never want to be seen as claiming I know what I am talking about on this forum at this stage of the game. I have seen the dielectric rating per millimeter for Rustoleum (perhaps it was the professional version) and it was 1400-1500. The brand "Spray On" "red insulating varnish" has a rating per millimeter of 2400. Perhaps it is because it is varnish... I don't know. I assumed that the high dielectric rating for Rustoleum was due to the fact that ions and electricity were connected in the minds of chemists who know these things and thus... "Spray On Varnish" brand I mentioned would also inhibit rust. Maybe I got wrong info on Rustoleum but I am a hundred percent sure I am right on Spray On Insulating Varnish. Varnish may all be high in this department for all I know.

Also - Scotch makes an insulating spray paint and its insulating factor per mm was 600 ish.. Looked all this up today but I may be wrong about Rustoleum. I thought a google search brought that up but maybe google was mixing info on the page. I brought up the pdf for Spray On brand and it is what I said.
 
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Sprayon Clear Insulating Varnishes - 16-oz. clear insulatingvarnish | Wayfair
This item features:
Penetrates old and new materials
Air-dries (10-15 minutes)
High arc resistance and non-tracking properties
Insulating varnish in Class F applications
Contains no chlorinated solvents
Abrasion resistant
DanVern™ standard valve
Smooth surface sheds dirt readily
Arc resistant for 100 sec on glass
Uses include general coating, impregnating, and insulation for electrical and electronic products
Capacity Wt.: 12 oz
Packing Type: Aerosol Can
Color: Clear
Full Cure Time @ Temp.: 60 min @ 77 °F
Dielectric Strength: 2200.0 V/mil
Applicable Materials: Most Metals, Wood
Resistance: Oil, Wear, Corrosive Process, Moisture, Grease, Acid, Alkali, Dirt

OK 2200 NOT 2500... It is still way up there!
 
Corrosion of Metals

The corrosion of metals is an electrochemical process. That is, it is an electrical circuit where the exchange of electrons (electricity) is conducted by chemical reactions in part of the circuit. These chemical reactions occur at the surface of the metal exposed to the electrolyte. Oxidation reactions (corrosion) occur at the surface of the anode and reduction reactions occur at the surface of the cathode.

I thought I was correct... ions.. electricity... rust... so it makes sense that a rust preventative would have a high dielectric rating.
 
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