What Kind of Silicone Coating is This?

[KDoug]

Hi,

I have a Dewalt DCS355 oscillating tool (power tool that cuts various materials through vibration) that I have made a repair. I had to take the circuit board out to make the repair and to do that I had to remove a lot of this "potting" type silicone that covered the board. I've looked around a good bit but most of the potting compounds I've seen online aren't silicone. The ones I have seen are usually a two part mixture and I'm not sure if that's what I need or not. Can y'all point me in the right direction of what I need. Attached are some photos.

Thanks

 

[dknguyen]

Those are probably epoxy.

 

[unclejed613]

**broken link removed**

you want to avoid the type of silicone that smells like vinegar (acetic acid) because it will corrode wiring, so don't use the silicone that you can get in a hardware store. the acetic acid is a byproduct of the adhesive polymerizing. make sure the silicone is of the "non-corrosive" variety.

 

[KDoug]

Those are probably epoxy.

I thought an epoxy was a hard substance, this stuff is soft and pliable.

 

[dknguyen]

I thought an epoxy was a hard substance, this stuff is soft and pliable.

I misread your question. Two-part is what you want since, whether silicone or epoxy, when potting anything it's too thick to properly air cure.

I have seen potting before that was slightly soft which also made me question whether it was epoxy or not. I think there are two parts silicones that exist.

 

[KDoug]

This company seems to have a variety of potting compounds for a reasonable cost. But they have too many options.

https://siliconesolutions.com/encapsulating-and-potting.html

 

[dknguyen]

The first one. SS-18.

 

[KDoug]

The first one. SS-18.

Which means what?

 

[dknguyen]

Which means what?

That's the stuff you want.

 

[KDoug]

The first one. SS-18.

Throwing out several options here. A couple of these look very similar, also most are platinum cure. Is that corrosive? Do you have any experience with the SS-18?

https://siliconesolutions.com/media/pdf/SS-8113TDS.pdf

https://siliconesolutions.com/media/pdf/SS-8112TDS.pdf

https://siliconesolutions.com/media/pdf/SS-6139TDS.pdf

https://siliconesolutions.com/media/pdf/SS-5061TDS.pdf

 

[dknguyen]

Wiki says:
Platinum-based cure system
In a platinum-based silicone cure system, also called an addition system (because the key reaction-building polymer is an "Addition reaction"), two different chemical groups (a silicone hydride and a vinyl) react in the presence of platinum (which serves as the catalyst). In this reaction, an ethyl group [C(H2)- C(H2)] is formed and there are no byproducts. Two separate components must be mixed to catalyze the polymers: one component contains a platinum complex which must be mixed with the second component, a hydride- and a vinyl-functional siloxane polymer, creating an ethyl bridge between the two. Such silicone rubbers cure quickly, though the rate of or even ability to cure is easily inhibited in the presence of elemental tin, sulphur, and many amine compounds.[1]

So it sounds like platinum-cure is not corrosive since there are no byproducts. Never heard of it before though.

 

[KDoug]

Wiki says:
Platinum-based cure system
In a platinum-based silicone cure system, also called an addition system (because the key reaction-building polymer is an "Addition reaction"), two different chemical groups (a silicone hydride and a vinyl) react in the presence of platinum (which serves as the catalyst). In this reaction, an ethyl group [C(H2)- C(H2)] is formed and there are no byproducts. Two separate components must be mixed to catalyze the polymers: one component contains a platinum complex which must be mixed with the second component, a hydride- and a vinyl-functional siloxane polymer, creating an ethyl bridge between the two. Such silicone rubbers cure quickly, though the rate of or even ability to cure is easily inhibited in the presence of elemental tin, sulphur, and many amine compounds.[1]

So it sounds like platinum-cure is not corrosive since there are no byproducts. Never heard of it before though.

Thanks, I had looked it up briefly, but I never saw where it was corrosive or not. I also looked up MG Chemicals RTV and the prices were much more costly.

 

[ChrisP58]

There are also many polyurethane based potting compounds for electronics.

 

[KDoug]

There are also many polyurethane based potting compounds for electronics.

There are also many polyurethane based potting compounds for electronics.

What would be some common cost effective ones for one job?

 

[dknguyen]

What would be some common cost effective ones for one job?

You should note it's really nasty (possibly impossible) to get back into something coated in polyurethane. That's part of the reason I go with silicone.

 

[KDoug]

Thanks for the comments y'all.

What would would be the best solvent or product to remove the old coating off?