[Solved] What are the keywords for finding silastic like silicon rubber glues/compounds?

Thread Starter

ballsystemlord

Joined Nov 19, 2018
102
No matter where I search to purchase this type of stuff, I get very few results and the prices are quite high, which is the opposite of what I expected considering how often I see this stuff used in electronics.
I'm assuming that I'm using the wrong keywords, or that there's a supplier or something I'm missing.

Any idea how to find this stuff?

Thanks!
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
102
Just like my searches, the one you suggested, Danko, also is mostly silicone products. Those that are silastic say that they are for "mold-making". I'm not sure if that means it can be used for molds and electronics, or if that means that it is used for molds and NOT electronics.
"DOW 4107656 SILASTIC RTV-3110 Off-White Mold-Making Base"
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
102
What about RTV substances.?
I had to look that up. Forgive my lack of knowledge about silicones, but is there any specific terms I should be looking for? I searched RTV and got results for gasket silicone, for sealant silicone (sounds very similar), and for high temperature silicone. Does it not matter the type as long as it's silicone?
 

WBahn

Joined Mar 31, 2012
27,942
No matter where I search to purchase this type of stuff, I get very few results and the prices are quite high, which is the opposite of what I expected considering how often I see this stuff used in electronics.
I'm assuming that I'm using the wrong keywords, or that there's a supplier or something I'm missing.
What is it you are trying to accomplish?
 

MrSalts

Joined Apr 2, 2020
2,628
Silastic comes in many different "grades". All are polydimethylsiloxane - as are most clear or white silicone rubber products. The different grades have different molecular weights of pre-polymer and differing numbers of "active sites" that can be cross-linked on curing and different curing modes (humidity cure, platinum catalyzed room temperature cure, thermal cure or UV cure).

Each grade makes a final product of different durometer (hardness) vs temperature and they have different stress vs strain curves and different elongation before yielding.

If a grade of silicone (silastic) is specified to make a mold, it is likely quite rigid and can be used for most rigid applications. If you want to mold something that is quite stretchy, the uncurled silastic will generally be low viscosity and you won't be able to free-form it, you'll need a mold. You can make a mold from high viscosity and more rigid silastic - some of these can be free formed.
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
102
What is it you are trying to accomplish?
I'd like to be able to service electrical equipment, I'm currently thinking of power bricks, that use this stuff. I'm thinking that when I repair something, I should put back in place the compound that I removed.
From what I understand, it's also a good idea to use this stuff to hold medium to large electrolytic capacitors in place.
 

MaxHeadRoom

Joined Jul 18, 2013
26,337
There are two kinds of potting compound i have traditionally come across, the solid epoxy where the unit is virtually destroyed if trying to access components.
The other is the RTV type compounds, where access is a great deal easier.
.
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
102
I'm referring to the type where it takes a razor to get it off of the components. But as long as you are careful, then you will not damage anything.
 

Ya’akov

Joined Jan 27, 2019
6,859
Among RTV adhesives there is a class called "electronics grade" (technically, neutral cure). The main difference from ordinary RTV is the lack of corrosive products when it cures. Ordinary types produce acetic acid, which is corrosive. It is a bad idea to use them inside sealed electronics unless you can be sure to fully cure the adhesive before closing it up.

I use ASI 388 with good results. It is not as rigid as the white, hard product used in a lot of products but it can be used in the same ways. It's not cheap but you can buy it in smallish tubes and I find I don't need that much so it tends to last. If you use a lot more, or can preserve a standard sealant cartridge you can save quite a bit. A more expensive option that might be more convenient is Chip Quick NCS10G-20G which is in very small tubes for spot application. Chip Quick makes solder, flux, and the like—so you know it is intended for electronics applications.

Epoxies are also an option, but they require much more complicated application. They are two part, and either you have to manually mix the components of have a dual nozzle dispenser. The latter isn't very helpful for spot application. I use Loctite EA 1C in tubes. It is very good general purpose high strength epoxy. It is very hard and not at all flexible. It can be machined or sanded if needed. I use it to lock down trimmers, adhere components to circuit boards if they need to be rigidly connected and there isn't an expectation of removal, and occasionally for repairs.
 
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