# Epoxy Question



## Mattaus (Oct 31, 2012)

Hi all,

In my flashlight mods and builds I tend to use a black electrical epoxy to seal circuits up but the only source available to me that sells the good stuff has them in packs far too large for me to use in one go - I spend $10 and throw out 90% of the material. 

Yes I can cut, measure and mix a smaller quantity, but I was just wondering before I go down that path if regular epoxy works as this is available more readily and in smaller and measurable quantities - even those 2-tube packs. Now the reason I'm asking other than trying to cut down on wastage is because the stuff I use is dedicated for circuit sealing...it's the proper stuff. As far as I was aware it was always colored but I have noticed around here people mixing GITD power with 'epoxy' and applying it to emitter bases etc so was wondering exactly what it was that they were using and if it was suitable for applying to PCB components.

Any suggestions?

Thanks,

- Matt


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## gadget_lover (Nov 1, 2012)

There are many different epoxies. Potting epoxies are non conductive. There are some metal filled epoxies.

As I understand, many of the colored potting epoxies are opaque to hide the components from those who would reverse engineer them. 

Daniel


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## kuksul08 (Nov 1, 2012)

I too have found it hard to get smaller quantities of potting compound, which is electrically insulating and thermally conductive. Interested in this as well.


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## Norm (Nov 1, 2012)

Matt $10 isn't expensive, you will pay close to that for smaller quantities from most hardware stores,

Norm


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## Mattaus (Nov 1, 2012)

Norm said:


> Matt $10 isn't expensive, you will pay close to that for smaller quantities from most hardware stores,
> 
> Norm



Yes $10 isn't expensive which is why up until now I've quite happily been throwing away 95% of what I mix. I guess I'm just trying to see if some of the 'other' epoxies are suitable because they generally come in those handy 2 packs squeeze tubey thingies lol.

If I have to keep using the encapsulant I get from JayCar then so be it. It does work _very_​ well and comes out looking nice. Just a shame to waste so much. Might have a crack at weighing and separating it this weekend.


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## arek98 (Nov 1, 2012)

Hmm, why are you throwing out 95% of it? I mix only amount I need (little more of course but nowhere close to 20 times required amount) and save a rest for few future projects. Unmixed epoxy has pretty long shelf lifev


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## Mattaus (Nov 1, 2012)

arek98 said:


> Hmm, why are you throwing out 95% of it? I mix only amount I need (little more of course but nowhere close to 20 times required amount) and save a rest for few future projects. Unmixed epoxy has pretty long shelf lifev



Partly because I've been lazy but mainly because I haven't had the time or the inclination to buy a scale sensitive enough to measure the small quantities I'm using. That been said I plan to do this from now on given the lack of alternatives and wanting to save instead of waste my epoxy from now on.


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## bshanahan14rulz (Nov 1, 2012)

Yeah, the larger the quantity you mix, the smaller your errors end up being in the final product. 

Also, potting compounds were designed to not expand or contract, not be conductive, and not have any capacitive or inductive effects. clear epoxy is meant to glue stuff together. If you are going to be playing with glow powders and tritium vials, definitely pick up some of that clear epoxy that comes in the bonded double-barrel syringe.

You can also go the extra mile and get some of the optical adhesive that the tomato fellow is selling in the marketplace. I used some of that to fill in a lanyard hole and put a trit in, and when it was done, it just looked like a tritium vial floating in the middle of the hole if you looked at it right. That stuff is used to glue lenses together in such a way that the interface does not affect light going through it like it would if you just put a lens next to another. The main point that people like about it (besides being really really clear) is that it is cured using UV, from sun or a lamp, <375nm. This means, if you don't get your powder/vial positioned just right within 5 mins, no biggie. It can also be cured in stages to provide varying degrees of viscosity.


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## Mattaus (Nov 1, 2012)

bshanahan14rulz said:


> Yeah, the larger the quantity you mix, the smaller your errors end up being in the final product.
> 
> Also, potting compounds were designed to not expand or contract, not be conductive, and not have any capacitive or inductive effects. clear epoxy is meant to glue stuff together. If you are going to be playing with glow powders and tritium vials, definitely pick up some of that clear epoxy that comes in the bonded double-barrel syringe.
> 
> You can also go the extra mile and get some of the optical adhesive that the tomato fellow is selling in the marketplace. I used some of that to fill in a lanyard hole and put a trit in, and when it was done, it just looked like a tritium vial floating in the middle of the hole if you looked at it right. That stuff is used to glue lenses together in such a way that the interface does not affect light going through it like it would if you just put a lens next to another. The main point that people like about it (besides being really really clear) is that it is cured using UV, from sun or a lamp, <375nm. This means, if you don't get your powder/vial positioned just right within 5 mins, no biggie. It can also be cured in stages to provide varying degrees of viscosity.



I have considered norland but how does it affect PCB components? That's my biggest concern. I'll probably purchase a digital scale this weekend and a few small plastic pots. that way I can split up the larger pack and just mix smaller quantities as needed. Should have really done this months ago but had too many other issues to contend with at the time :/

Live and learn!


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## Norm (Nov 1, 2012)

Matt you may be able to buy 50Ml or 20Ml syringes from your vet or pharmacy to store your excess.

No problem with accuracy, no need to weigh.

Norm


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## PCC (Nov 2, 2012)

Most two-part clear epoxies will discolor with time. I've mixed glow powder into clear two-part epoxy and after about three months it's a brownish color.


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## precisionworks (Nov 4, 2012)

Mattaus said:


> I have considered norland but how does it affect PCB components?


I've never used Norland 121 or Norland 123 but the specs look correct for what you need. If pricing is similar to NOA61 it may be more costly than what you now use.

http://www.apm-technica.com/media/downloadcenter/pdf/tdb/TDB%20APM%20114600.pdf


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## Mattaus (Nov 4, 2012)

precisionworks said:


> I've never used Norland 121 or Norland 123 but the specs look correct for what you need. If pricing is similar to NOA61 it may be more costly than what you now use.
> 
> http://www.apm-technica.com/media/downloadcenter/pdf/tdb/TDB%20APM%20114600.pdf



Well at the moment I'm using encapsulant epoxy and its about $10 for 300ml, which is stupid cheap really. May as well keep using that and split it up properly. I got my mix wrong yesterday and it never set but I managed to get it right the second time :/


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## VegasF6 (Nov 4, 2012)

Why don't you try RTV silicone, no mixing no fuss. Is it too thick for your needs?


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## moderator007 (Nov 4, 2012)

VegasF6 said:


> Why don't you try RTV silicone, no mixing no fuss. Is it too thick for your needs?


I was going to suggest the same thing. I have used the 100% clear silicone tooth paste tubes at lowes several times for sealing components. Can be removed later if need but not the easiest of task.


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## Yoda4561 (Nov 4, 2012)

The curing agents in most silicones are not good for sensitive electronics, acetic acid is often involved. They do make special RTV's which are okay to use on electronics. Not sure about the household clear silicones, but whatever silicone you use, if it's not rated for electronics give it a good long test period on something before you use it on a bunch of lights/boards.


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## Mattaus (Nov 4, 2012)

Yoda4561 said:


> The curing agents in most silicones are not good for sensitive electronics, acetic acid is often involved. They do make special RTV's which are okay to use on electronics. Not sure about the household clear silicones, but whatever silicone you use, if it's not rated for electronics give it a good long test period on something before you use it on a bunch of lights/boards.



This is exactly what I was worried about when I first asked. Maybe not directly but this was my concern when I was looking for alternatives to what I knew worked.


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## Norm (Nov 4, 2012)

Here
Google

Norm


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## VegasF6 (Nov 4, 2012)

Its easy to buy neutral cure silicone at the big box home stores.

*edit*
Here is an example. This one I THINK is neutral cure. 
Of course, you can't build these up the way you would with a liquid 2 part epoxy or 2 part RTV or molding rubber or even a 1 part UV cure, but I don't really know your needs either. If for instance you are trying to fill a potting box you would probably have to do it in stages to ensure it dries all the way through.


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## Mattaus (Nov 6, 2012)

Norm said:


> Here
> Google
> 
> Norm



Norm,

That looks like gold. One part sealants. Sounds like heaven to me. I'll have to grab a sample from somewhere and see how it goes 




VegasF6 said:


> Its easy to buy neutral cure silicone at the big box home stores.
> 
> *edit*
> Here is an example. This one I THINK is neutral cure.
> Of course, you can't build these up the way you would with a liquid 2 part epoxy or 2 part RTV or molding rubber or even a 1 part UV cure, but I don't really know your needs either. If for instance you are trying to fill a potting box you would probably have to do it in stages to ensure it dries all the way through.



I generally don't need a lot in one go. A small shot glass worth of epoxy is normally twice as much as I need.


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## archer6817j (Nov 7, 2012)

I normally just eyeball when I mix 2 part epoxies. I don't think you need to weigh it. If the proportions are off it will just cure faster or slower than its supposed to, but it will still cure...unless you are way off.


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## Mattaus (Nov 7, 2012)

archer6817j said:


> I normally just eyeball when I mix 2 part epoxies. I don't think you need to weigh it. If the proportions are off it will just cure faster or slower than its supposed to, but it will still cure...unless you are way off.



Yeah that's what I've started doing. I got my first mix wrong (it went everywhere it wasn't supposed to go and didn't stay where I want it to haha) but since then I've seem to nailed it down pretty well. Progress is gooooood


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## Yoda4561 (Nov 7, 2012)

archer6817j said:


> I normally just eyeball when I mix 2 part epoxies. I don't think you need to weigh it. If the proportions are off it will just cure faster or slower than its supposed to, but it will still cure...unless you are way off.



With 1:1 by volume mix ratio epoxys (most consumer grade stuff) this is the way to go, the ones with the 5:1 by weight mix ratios or 2/5ths by volume or whatnot are a bit trickier to get just right without gradated cups or a small scale.


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## Mattaus (Nov 8, 2012)

Yoda4561 said:


> the ones with the 5:1 by weight mix ratios or 2/5ths by volume or whatnot are a bit trickier to get just right without gradated cups or a small scale.



And that's exactly what I use (epoxy...not the cups). It does eventually dry as mentioned previously. It just takes a bit longer. my first mix took days lol. WAY off.


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## archer6817j (Nov 8, 2012)

Ah 5:1 is a good point. What if you printed two different size circles on a piece of paper as a rough guide? Not accurate per se but it might be better than nothing  

Or, you could get a couple of graduated dispensing syringes from McMaster and load them full from the original tubes. I like that better  makes me wonder why they don't package it that way!


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## Walterk (Nov 28, 2012)

archer6817j said:


> If the proportions are off it will just cure faster or slower than its supposed to, but it will still cure...unless you are way off.



Within margins, yes.
To be precise only part of the epoxy will cure, so the final product will not meet the specs and will behave not as expected.
Most likely you wouldnt notice the difference, but it could show on the long term.
The resin for epoxy is most times not that harmfull, but the hardener usually has an acid nature in it.
For a divelight for example I would find it critical, I would weight when sealing or bonding.


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