Epoxy Resin Blues

Does anyone have any tips or techniques for removing generous quantities of epoxy resin from crossover components mounted directly on a loudspeaker recess tray. In the past I've found a little gentle flexing was sufficient to cause the resin to break away but in this instance this has not worked.

Cutting the resin away with a sharp knife is the other option but as the components are hard wired to each other this would mean cutting around the component leadout wires.

Any ideas?

 

There are in fact fluids which solve epoxi, quite strong stuff. I'm afraid I don't know the name of it but those who sell epoxi have this also.

If you don't have his stuff, only mechanical methods will do, like a knife etc.

 

What about sticking the component in the freezer for a while, (If it fits) may make reson more brittle and easier to remove components.

 

Thanks PA and AK.

I did think of polymer solvents but I'm not keen on using chemicals because they may affect the epoxy/plastic sealing on the crossover caps. I think I'll try the freezing approach with a can of this stuff from RS. Drops temps down to –51C.

 

Because epoxy resins are crosslinked (essentially the thing is one very large molecule), only materials that either react with and break down the epoxy or soften it would work, and they would have to be very strong, as epoxies are noted for their chemical resistance. Personally, I wouldn't like to handle either (I've no idea what they would be), so the freezing route (taking the resin below its glass transition temperature, where it becomes glassy and therefore brittle) seems to be the best bet.

 

I'd freeze and attack with a chisel & hammer ...with caution of course. It should become more brittle with decreasing temp.

 

Isn't epoxy very resiliant to temperature? Its used for composite aeroplane bodies so that must get to -50 odd at altitude and 400-500mph (probably, wild guessing ).
Acetone is generally recommended for epoxy removal, which just happens to be in nail varnish remover.

 

There are epoxies and epoxies. The aircraft stuff works according to the same basic mechanism as the stuff you buy at the local DIY, but there all resemblance ends. And you also used the magic word "composite" - the aeroplane stuff is not epoxy resin alone, but is reinforced and stiffened with fibres. AFAIK, acetone and similar polar solvents (alcohol) are good for removal of epoxy before the stuff sets, not so good afterwards. Acetone is a fiercer solvent than ethanol, but it would take a while to dissolve a fully set epoxy.

 

I'm assuming the type of epoxy on my crossovers is the common 'araldite' type of epoxy resin (since the maximum altitude of me speakers is about 24†).

If freezing doesn't work I'll try a hot-knife on the stuff.. :MILD:

Thanks for the info.

 

I thought it was all the same stuff? They make bike frames with actual brand name araldite.
Tones: Yes I do realise that the plane isn't just sculpted from epoxy but I thought it was effectively just carbon fibres (or something) basically soaked in araldite? So the glue still has to withstand the low temperatures.

That freeze spray looks like it could be fun

 

Well if you never here from me again it's cos me fingers have shattered in Royal-Institute-Christmas-lectures-sausage-and-liquid-nitrogen kinda way!

 

The chemical that disolves cured epoxy is called pyridine, and is quite unpleasant stuff and difficult to get hold of unless you work in a chemistry lab, as I did some years ago. And as you mentioned Mosfet, it's probably just as effective at disolving plastic cap cases. So be careful with that freezer can and let us know how you get on.

 

You have to remember that ARALDITE is a trade mark and not the name of a specific material. The mark is used on a wide range of materials, from the Bisphenol A-based resin of what you call "Araldite" to specialised engineering and technological materials.

All epoxy resins have in common an adhesive and a hardener. The adhesive has the epoxy groups, a triangular item of two carbons and an oxygen, which is highly strained chemically and is therefore very reactive. The hardener is an amine. Now the nature of the molecules to which the epoxy groups on the one hand and the amine groups on the other are attached can be very different and their natures change the final properties of the hardened material considerably.

Here's a good guide to the basic chemistry of the process:

http://www.pslc.ws/mactest/epoxy.htm

This one gives some idea as to the variety of epoxies:

http://www.gluguru.com/ciba.htm

ARALDITE (ARALDIT in German, because they pronounce the final "e") is now made by Vantico, a spin-off of Ciba Specialty Chemicals that resulted from the great Ciba-Geigy/Sandoz merger of 1995 to form Novartis, and that also resulted in my sitting where I'm now sitting!

 

Are you sure, John? I've never heard of pyridine being used to dissolve epoxies. It is indeed used as a solvent, and it is a thoroughly unpleasant material:

Pyridine is an organic liquid of disagreeable odour, produced from coal-tar or by chemical synthesis. It is widely used as a solvent and intermediate in the production of piperidine, agricultural chemicals, drugs, dyestuffs, paints, rubber products, polycarbonate resins and textile water-repellents, as well as in laboratories. Occupational exposure may occur through inhalation and dermal contact during its production and its various uses as well as during the processing of oil-shale and at coke-oven works. It is rarely detected in ambient air or drinking water but is frequently found in indoor air. It is present in cigarette smoke and in the volatile components of certain foodstuffs.

In short, to be avoided, if possible.

 

Thanks, everything I ever wanted to know about epoxy resins

 

Paint stripper (methylene chloride) will dissolve / rot many common epoxy resins such as Araldite. Unfortunately it will probably also make a mess of most of the components on the PCB.

Google for "methylene chloride" or "dichloromethane" and you will get lots of health and safety fact sheets, which basically tell you it is pretty nasty stuff and possibly a carcinogen.

Hope this helps

 

Originally Posted by tones
Are you sure, John? I've never heard of pyridine being used to dissolve epoxies. It is indeed used as a solvent, and it is a thoroughly unpleasant material....

Quite sure tones, while I was working in the chemistry lab, a colleague used some pyridine for just that purpose, to release a thermocouple that had been Araldited into a piece of aparatus - it was left soaking for 24 hours in the back of a fume cupboard.