Big problem: Nylon & HCl Help!

[Bertho]

I have a mixture of connectors attached to PCB strips with solder so I tested a handful with hot HCL diluted 50% and it worked fine, all the solder was gone.
I then repeated with 1.4kg of connectors and this time I got a gooey black stuff that stuck to everything. I eventually figured out that there were nylon connectors in the big batch and none in my test batch.
Boiling water will not remove it, neither acetone nor alcohol.
How can I remove the coating or any suggestion on how to proceed?
Bertho

 

[geedigity]

It depends, but since a 50% solution of HCl (starting with a 31% HCl?) and 50% water is starting to dissolve the plastic, try full strength HCl on a small batch and see if it makes the plastic soluble enough to rinse away.

 

[Bertho]

Thanks,
I will try 32% HCl.
I also tried a paint stripper without success.
Bertho

 

[geedigity]

I did a little searching on the web and it appears there are several types of nylon in use, each being affected by different solvents. I would think the best way to cure the problem would be to incinerate. However, this would require the exhaust/smoke to be run through a scrubber or afterburner. Maybe pyrolizing would work in your situation, and following pyrolsis, burn off the carbon.

 

[Bertho]

I have thought about the pyrolysis process but I am hesitant to build the equipment since this is a hobby and I am already spending way too much time by creating problems like this mess with Nylon. It would be interesting though.
I have been collecting electronic scrap for decades from old test equipment and other electronics that I by chance have found but I am running out of material. So far I have recovered 43 grams so I am happy about each successful procedure done.
I still have to come up with a procedure to remove very old soldermask off gold plated PCBs from HP test equipment but first I need to resolve this Nylon problem.

 

[snoman701]

Leave the boards out in the sun....can't remember who posted it, but it works.

Still not really worth it though...even with Hp stuff.


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[Bertho]

The goal is not to make money since it a hobby. Of course, obtaining the gold at the end is the reward for learning the process and overcoming the challenges.
I searched for the message about leaving the parts in the sun. It sounds strange but ultraviolet light breaks down many material. It does not sound practical since there are many shaded spots where the UV light would not reach.

 

[chemtag]

A handy digestion of plastics that I have found (but never had a reason to try) is:

for every 1 g of plastic, add 10 mL of concentrated HNO3 and 10 mL of concentrated H2SO4 and heat the solution to boiling for 1-2 hours. The addition of H2O2 towards the end of the reaction can be used to clear the solution.

The procedure doesnt specify what concentration of H2O2, but most likely the author was using 30%. Similarly, they were probably using 65% HNO3 and 93 or 98% H2SO4. No idea if this works for Nylon or not, but may be worth trying some 1:1 mixture of nitric and sulfuric, and then heat it up real good.

Moderator's Note: This would be a very dangerous combination. Hot sulfuric acid with an oxidizer like either nitric acid or hydrogen peroxide is extraordinarily hazardous and should not be attempted by anyone who does not understand the hazards.

FrugalRefiner

 

[cosmetal]

A handy digestion of plastics that I have found (but never had a reason to try) is:

for every 1 g of plastic, add 10 mL of concentrated HNO3 and 10 mL of concentrated H2SO4 and heat the solution to boiling for 1-2 hours. The addition of H2O2 towards the end of the reaction can be used to clear the solution.

The procedure doesnt specify what concentration of H2O2, but most likely the author was using 30%. Similarly, they were probably using 65% HNO3 and 93 or 98% H2SO4. No idea if this works for Nylon or not, but may be worth trying some 1:1 mixture of nitric and sulfuric, and then heat it up real good.

I do believe that this is called "wet ashing" :shock:

If so, it is a very nasty and widely discouraged process :!: :shock: :!:

Hopefully, one of GRF's experts will confirm my suspicion or send me to the back of the class! :?: :?:

James

 

[cosmetal]

Yep! I think I was right . . .

Read Mr. goldsilverpro's excellent "condemnation" (and scary :shock description of it's horrors at:

https://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=26296&p=279038&hilit=wet+ashing#p279038

James

 

[snoman701]

The goal is not to make money since it a hobby. Of course, obtaining the gold at the end is the reward for learning the process and overcoming the challenges.
I searched for the message about leaving the parts in the sun. It sounds strange but ultraviolet light breaks down many material. It does not sound practical since there are many shaded spots where the UV light would not reach.

I actually had some in a pretty shaded area and they still deteriorated in about a six month period.


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[snoman701]

The above reference is not only wet ashing, but the addition of nitric makes it a piranha solution as well. One could end up in a world of hurt (potential explosion of concentrated sulfuric acid) way too easily.


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[Topher_osAUrus]

I think piranha solution refers specifically to concentrated sulfuric with peroxide as the oxidizer, (think it needs to be concentrated h2o2 as well, so it doesnt decomp as fast -that may be inaccurate though)

The main issue I see with sulfuric and nitric mixed together, is someone who is unfamiliar with its reactions could inadvertently have some cellulose in the digestion and make something that goes boom. Those two acids can nitrate a myriad of things.

They can also dissolve a whole lot of different materials, your flesh being one of them. Quite happily and readily in fact, and, still keep diggin down to the bone until you neutralise it.

 

[chemtag]

Yep! I think I was right . . .

Read Mr. goldsilverpro's excellent "condemnation" (and scary :shock description of it's horrors at:

https://goldrefiningforum.com/phpBB3/viewtopic.php?f=60&t=26296&p=279038&hilit=wet+ashing#p279038

James

Wow, I had no idea. Thanks for letting me know. Good thing I never tried it!

I am new to this community (as my post count and join date clearly display) and am new to a lot of the techniques/chemistry that is discussed here. I have used fuming nitric + concentrated sulfuric heated to reflux before, but for organic chemistry purposes (great nitrating conditions, as you can imagine). Perhaps most importantly, it was on a very small scale (< 100 mL total solution) relative to what appears to be common with this community.

I have more experience with piranha solution, which is Sulfuric and Peroxide together. The danger with that, other than its extreme reactivity, is that when you add the peroxide you generate an enormous amount of heat, enough that it can be quite surprising to people and result in boil overs or pressurizing vessels. I have only ever worked on it on small scale for cleaning, or slightly bigger scale for attempted digestions of stubborn materials (in which it has never worked).

 

[Tirtho111]

hello............
It depends, but since a 50% solution of HCl (starting with a 31% HCl?) and 50% water is starting to dissolve the plastic, try full strength HCl on a small batch and see if it makes the plastic soluble enough to rinse away.
i think this will help you..............

 

[autumnwillow]

Rinse well with water, dry and incinerate. No need for wet ashing. Too dangerous on your end.