That was some nasty stuff! It's a known carcinogen and can lead to a host of respiratory, neurological and other illnesses. Trichloroethylene is a related substance and part of the legacy in Woburn MA, in the incident recreated in the movie "A Civil Affair".

Been bugging me since I posted, I was thinking when we pronounced it, it had "lene" on the end rather than "thane". I think you have hit the target by mentioning Trichloroethylene, that is what I was trying to remember. We used it for all kinds of stuff, always had a container on my bench. One of the Hughes engineers once told me it gets inside the molecules in the epoxy and expands causing it to break apart. It doesn't melt it like some chemicals will do on plastic.

Ya, it is a wonder we are not dead from the stuff we have used. Like holding tin-lead solder in your mouth causes lead poisoning, I should be long dead, been doing it for 60 years.

 

If what you want to remove the coating from is a coil/inductor, I hope you do your testing on it before using chemical strippers. And that you aren't hoping to use the item again. Any stripper that removes the conformal coating is also going to remove the insulation on the wire of the coil. Also when using strippers on boards to see the circuit components they will also remove markings from ICs, color bands from resistors, capacitor markings.... All of the markings and insulation of magnet wire are way less chemical resistant than the conformal coating.

 

I hope you do your testing on it before using chemical strippers. And that you aren't hoping to use the item again.

Yeah, I had thought about that too. I've already done the testing and have all the data I need before I practically destroy the part. What I'm trying to do is to reverse engineer the thing. Also, I actually have several of them.

 

If what you want to remove the coating from is a coil/inductor, I hope you do your testing on it before using chemical strippers. And that you aren't hoping to use the item again. Any stripper that removes the conformal coating is also going to remove the insulation on the wire of the coil. Also when using strippers on boards to see the circuit components they will also remove markings from ICs, color bands from resistors, capacitor markings.... All of the markings and insulation of magnet wire are way less chemical resistant than the conformal coating.

That is simply not true. A lot of conformal coatings are acrylic lacquers. Lacquer remover (e.g., acetone or ethyl acetate) does not remove modern insulation from magnet wire. I don't know about the markings, but certainly enamels are more chemically resistant than acrylic lacquers.

John

 

That is simply not true. A lot of conformal coatings are acrylic lacquers. Lacquer remover (e.g., acetone or ethyl acetate) does not remove modern insulation from magnet wire. I don't know about the markings, but certainly enamels are more chemically resistant than acrylic lacquers.

John

You sure about that? Many of today's magnet wires are coated with a polyvinyl surfaces, and are soluble in acetone. And up until now I don't remember lacquer thinners/removers being mentioned. I was talking about the methyl type removers/paint strippers.

 

Obviously, you should have constructed the sentence in bold with a lot more care. "Any stripper" is not ambiguous and is wrong. If you have scientific or technical references to refute that, please do. Moreover, Formvar is insoluble in the two solvents I mentioned, namely ethyl acetate and acetone. Other common magnet wire insulation, such as nylons, polyesters, polyimides, and polyurethanes are also insoluble in common lacquer solvents. Some of those insulations are particularly insoluble in any solvent one is likely to have.

Source: http://www.2spi.com/catalog/submat/vinylec-solubility.html



John

 

Obviously, you should have constructed the sentence in bold with a lot more care. "Any stripper" is not ambiguous and is wrong. If you have scientific or technical references to refute that, please do. Moreover, Formvar is insoluble in the two solvents I mentioned, namely ethyl acetate and acetone. Other common magnet wire insulation, such as nylons, polyesters, polyimides, and polyurethanes are also insoluble in common lacquer solvents. Some of those insulations are particularly insoluble in any solvent one is likely to have.

Source: http://www.2spi.com/catalog/submat/vinylec-solubility.html

View attachment 76603

John

Thanks for the info, John
Please enlighten me, I personally don't care much if the coating in the coil is destroyed (though it would be better if it didn't). Do you think acetone would work to get rid of the epoxy? Would you use it for this application, or would you stick to the list of 4 solvents (dichloromethane, TCE, NMP and THF) recommended by Gopher?

 

Epoxy is a class of polymers. Some are more chemically resistant than others. Acetone will not dissolve a polymerized epoxy resin. Upon soaking, it may soften it a little. We are not completely sure your potting material is an epoxy, but for easy reference that is what I will call it.

The solvents suggested by Gopher, to which you might add hexamethylphosphoramide (HMPA, http://en.wikipedia.org/wiki/Hexamethylphosphoramide), dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), butyl cellosolve, and acetonitrile, are excellent solvents and/or have different solvent properties than acetone.*

One rule about solvents to remember is that "like dissolves like." With a polymer like epoxy, you are not likely to find a solvent in the strictest sense. By that I mean something that dissolves it, which if then allowed to evaporate will leave the original epoxy. What you may find is something that softens the epoxy, disrupts, and/or denatures it so it can be more easily removed (see: next paragraph for the context in which I am using those words).

Let me give an example. Assume you have a lacquer, even fingernail polish. You can use a solvent like ethyl acetate or acetone to remove it, and if you allow the solution you now have to evaporate, you will get a residue just like the original lacquer. That is one of the nice things about lacquer finishes -- repaired areas melt into the existing finish and can be virtually indistinguishable from the original. On the other hand, if you have a hardened enamel or polyurethane, like modern automotive paints, a simple solvent won't dissolve it, but a paint remover will make it wrinkle up and soften so it can be easily scraped off. The scrapings do dry and get hard, but they are not at all like the original paint. For the sake of discussion, call that "denaturing" as opposed to "dissolving."

You will find that many paint removers, which claim to be effective on "all finishes," will contain dichloromethane, methanol, acetone, toluene + other things. Some versions may have NMP, which is a modern and very useful solvent. Such products both dissolve and denature the finish. For enamels, epoxies, and polyurethanes, the predominate action is to denature.

Of the solvents mentioned by Gopher, I would probably pick dichloromethane (or chloroform) and NMP (http://en.wikipedia.org/wiki/N-Methyl-2-pyrrolidone). Dichloromethane is very low boiling and is flammable. Chloroform is an alternative. It is not as strong a solvent, but it has a higher boiling point and is not flammable. NMP is used in commercial paint strippers. I have had experience with Peel Away-7 (https://www.dumondchemicals.com/pro-peel-away-7.html), which is based on NMP. I would not mix dichloromethane/chloroform and NMP without being sure they were completely compatible. My concern is not so much the compounds themselves, but impurities and degradation products those solvents might contain. A product like Peel-Away 7 may contain other chemicals as well.

Here's what I would do. Start with either an NMP-based or a dichloromethane-based paint remover. In the US, both are still available, while buying the individual chemicals has become more difficult. Soak the "epoxy-potted" device in it overnight. Check it occasionally and see if the epoxy is softened sufficiently to facilitate removal. If you can physically (e.g., grind) remove some of the potting material before soaking, that will help. Please let us know what happens. There are still more vigorous things that can be done, short of using HF or hydrazine as mentioned above. The advantage of starting with the two paint removers is that you will be left with an electronic circuit. It may not work, but the parts will still be there.

Finally don't forget about heat and boiling water. Those may soften the potting compound enough to facilitate removal. Also, grinding, picking, and media blasting may do the job. Remember, dinosaur fossils are recovered from rock without using solvents.

John

*Solvent strength is a very complex subject. If you take ordinary sugar, water is a great solvent for it. Dichloromethane is not. On the other hand, water won't dissolve polystyrene, but dichloromethane will. "Solvent strength" is used very loosely and in the context of what is being dissolved.

 

Here's what I would do. Start with either an NMP-based or a dichloromethane-based paint remover.

Thank you John, for your elaborate answer. I'll start with your suggestion... one thing that hasn't occurred to me until now, is that I would really, really hate it if this thing turned out to be PVC (though I doubt it, I've never heard of PVC being used as a potting compound before)
In any event, I think I already know how to test for that, as shown here.

I'll try to get this done through the weekend, and then I'll get back to all of you.

 

Acetone or methyl ethyl ketone (MEK) will instantly attack PVC, or try some plumbing cement for PVC pipe. PVC also gives a fairly acrid flame test. BTW, if it is a choice of which to do first, I would go with NMP. Dichloromethane-based solvents have been tried with limited success. If the NMP gives a gooey mess, that can be cleaned up with almost any of the solvents we have discussed.

I am anxious to read your results. Be sure to remove as much as practical by physical means first. That is much faster, but perhaps not as thorough.

John

 

Acetone or methyl ethyl ketone (MEK) will instantly attack PVC, or try some plumbing cement for PVC pipe. PVC also gives a fairly acrid flame test. BTW, if it is a choice of which to do first, I would go with NMP. Dichloromethane-based solvents have been tried with limited success. If the NMP gives a gooey mess, that can be cleaned up with almost any of the solvents we have discussed.

I am anxious to read your results. Be sure to remove as much as practical by physical means first. That is much faster, but perhaps not as thorough.

John

Hey great idea! I have some PVC cement with me here, see if the thing attacks it... gonna go and try... why didn't I think of that before????)

 

Nope.... the thing's definitely NOT PVC... so that's a relief (kind of)... I put a little PVC cement on it and it didn't do a thing
Now I'm gonna head to my chemical supplier and see if I kind find some NMP based compound

 

Sherwin Williams carries Peel Away in the US. Peel Away 7 (the NMP stuff) cost about $24/container a few years ago. Also, SW is pretty liberal with 20% discounts. Doesn't hurt to ask.
John

 

Sherwin Williams carries Peel Away in the US. Peel Away 7 (the NMP stuff) cost about $24/container a few years ago. Also, SW is pretty liberal with 20% discounts. Doesn't hurt to ask.
John

Just got back from Home Depot. Bought a quart of paint remover made by Klean Strip, Premium Sprayable (not gonna spray it though) it says in the label that it's able to remove epoxy and polyurethane, among other things. Listed ingredients are: milk, sugar and flour (just kidding) ... ingredients are: Ethanol, Isopropanol, less than 4% Methaol, Methylene Chloride, Nonyphenoxpolyethoxy-ethanol

Do you think I should give it a go?

 

Just got back from Home Depot. Bought a quart of paint remover made by Klean Strip, Premium Sprayable (not gonna spray it though) it says in the label that it's able to remove epoxy and polyurethane, among other things. Listed ingredients are: milk, sugar and flour (just kidding) ... ingredients are: Ethanol, Isopropanol, less than 4% Methaol, Methylene Chloride, Nonyphenoxpolyethoxy-ethanol

Do you think I should give it a go?

You should have looked for the KLEAN STRIP KS-3 PREMIUM STRIPPER.
http://www.homedepot.com/p/Klean-St...m-Stripper-GKS3/100144685#product_description
The safety datasheet says:
60 to 100% Methylene chloride
10-30% Methanol
1 - 5% Stoddard Solvent (aka: Mineral Spirits)

Ratios are normally tuned to local laws. First ingredient listed is usually the highest concentration. Looks like Methylene chloride is lower volume additive in your version.

 

Well, since you have it, give it a try. Those ingredients translate to methylene chloride (aka dichloromethane) a thickener/surfactant and some alcohols. The nonylphenoxyphenylethoxy-ethanol is a surfactant (http://pubchem.ncbi.nlm.nih.gov/compound/7700?from=summary#section=Top). The carbon chain on the phenyl ring has nine carbons, hence the "nonyl". The really active ingredient is the methylene chloride.

As mentioned, methylene chloride is flammable and highly volatile. It is hard to find gloves that are not attacked by it. Your typical painter's gloves will be destroyed instantly. Neoprene will work for a little while. Just be careful about getting it on your skin and use in a ventilated area. On moist bare skin, it may give an intense burning sensation. I have survived many exposures and never lost any skin to it, despite that burning feeling.

If it doesn't work, I would still give NMP a try. It is quite different. I first used it 12 years ago on a plaster ceiling with 50 year's worth of paint -- at least 12 layers of oil-based and latex. It liquefied all of that paint overnight. I did not like the messy cleanup of the goo, so I went back to Peel Away 1, which is basically a poultice of lye and clay/lime. For your purpose, though, the gooey mess from NMP is a non-issue and may be an advantage.

John

 

You should have looked for the KLEAN STRIP KS-3 PREMIUM STRIPPER.
http://www.homedepot.com/p/Klean-St...m-Stripper-GKS3/100144685#product_description
The safety datasheet says:
60 to 100% Methylene chloride
10-30% Methanol
1 - 5% Stoddard Solvent (aka: Mineral Spirits)

Ratios are normally tuned to local laws. First ingredient listed is usually the highest concentration. Looks like Methylene chloride is lower volume additive in your version.

They had three varieties at my local store, and the one I got is the only one with that ingredient...
On the other hand, its datasheet says (on page 3) that it has 71% Dichloromethane and 24% Methanol ... doesn't sound that bad.
What's the worst that could happen? If the reaction is too slow then I'll buy the industrial grade stuff on monday...

 

Sorry, we cross posted. 71% methylene chloride should be plenty. You are lucky to be able to get such things at HD.

John

 

Sorry, we cross posted. 71% methylene chloride should be plenty. You are lucky to be able to get such things at HD.
John

Just placed the thing in a (pickle) glass jar, and put a lid on it ... I pocked a hole on the lid to allow it to release any gasses generated by the reaction. The red paint coating on the thing immediately started to peel off, but the black epoxy seems untouched so far (about 3 minutes) ... I'm going to place this on a high shelf outside by the laundry, and take a look every 6 hours or so ... see how things are going.
It's kind of fresh down here, about 20°C (68°F), and we're expecting temperatures in the next few days as low as 16°C (61°F) and as high as 23°C (73°F)... wonder if this will affect the reaction speed ... this is going to test my patience ...

 

Methylene chloride's boiling point at sea level is 39.6°C. I think you will be OK with those temperatures. The vent in the lid was a good idea. John