Does Silicone Bond to Acrylic

sleepydoc

sleepydoc

Team RC
Ok, all us know that it doesn't, but I still see people claiming it does, or saying things like "I can pick up my sump but the baffles."

Below are some pics of the acrylic baffles that I had siliconed into my 40b sump. They had been in place for 3 years until I cut them out yesterday to move and re-do my sump. The top pic shows a strip of silicone along the edge of the baffle. In the bottom pic I simply pulled the silicone off with my fingers. It all came off in one piece, with no scraping. Note the completely clean surface of the silicone.

I could also lift the sump by the baffle, but only because there was a small lip of silicone over the top edge of the baffle, adhering to the glass wall of the sump, so when I pulled up on the baffle it would wedge against this. There was no contribution of the silicone adhering to the acrylic baffle.


IMG_1332_zpskvkxagnd.jpg


IMG_1333_zpsiiiivmdv.jpg
 
Have you seen this? Silicone Product Test on Acrylic: https://youtu.be/mReJB4qc9QU

I used this when I attached my acrylic overflow to my glass tank. Obviously there isn't much stress involved but I have had no problems with leak down. But this guy's video shows there is at least one product out there that has some potential (maybe still somewhat limited).
 
In my experience it does not adhere to it. But I still use silicone and acrylic in my glass sumps. I just make sure to put silicone on both sides. That seams to work for me at least.

Will
 
I think in certain applications it is perfectly acceptable. Such as sump baffles. If you can lift the sump up by the baffles then it will probably hold that 2-4" water level differential. People have been using silicone to glue in overflows forever. I personally had a corner overflow made out of black 1/4" acrylic that I installed 10 years ago using cheap GE silicone. It took me 30 minutes to get it out and clean up the tank with a razor blade. But no, I wouldn't construct and tank and butt glue two pieces of acrylic like you would a glass tank.
 
supervdl said:
As far as I know it does not bond.
Click to expand...

DeepSeaBeauti said:
In my experience it does not adhere to it.
Click to expand...

Yes, that's my point; silicone does not bond to acrylic, but there are still people claiming it does so I posted this to show the lack of adhesion.

DeepSeaBeauti said:
But I still use silicone and acrylic in my glass sumps. I just make sure to put silicone on both sides. That seams to work for me at least.

Will
Click to expand...

thejuggernaut said:
I think in certain applications it is perfectly acceptable. Such as sump baffles. If you can lift the sump up by the baffles then it will probably hold that 2-4" water level differential. People have been using silicone to glue in overflows forever. I personally had a corner overflow made out of black 1/4" acrylic that I installed 10 years ago using cheap GE silicone. It took me 30 minutes to get it out and clean up the tank with a razor blade. But no, I wouldn't construct and tank and butt glue two pieces of acrylic like you would a glass tank.
Click to expand...

Yes, you can use it to 'wedge' baffles in place, provided you are aware of and account for the issues related to acrylic expansion causing stress on the sump walls. There is not a huge pressure difference between the two compartments, and the bond with glass is so good that it really doesn't matter if it bonds to the acrylic. After I turned off the power to my tank, the water levels in the sump chambers equalized over a day or so, so there was some slow leakage, but for a sump that really doesn't matter. If you are depending on it to be water tight and not leak, it absolutely will not work.

I have no experience with the "Silicone for Plastics," so I can't comment other than to say that the materials properties of glass and acrylic are very different, so make an adhesive that adheres to both is not easy. Without good data and experience I would be hesitant to use it in a critical application.
 
Raul-7 said:
I siliconed my acrylic overflow box to my glass aquariums, works fine.
Click to expand...

Internal or external. If external, you like to live dangerously. There is no structural bond between silicone and acrylic. The physical properties of the acrylic make that impossible.
 
sleepydoc said:
Yes, that's my point; silicone does not bond to acrylic, but there are still people claiming it does so I posted this to show the lack of adhesion.





Yes, you can use it to 'wedge' baffles in place, provided you are aware of and account for the issues related to acrylic expansion causing stress on the sump walls. There is not a huge pressure difference between the two compartments, and the bond with glass is so good that it really doesn't matter if it bonds to the acrylic. After I turned off the power to my tank, the water levels in the sump chambers equalized over a day or so, so there was some slow leakage, but for a sump that really doesn't matter. If you are depending on it to be water tight and not leak, it absolutely will not work.

I have no experience with the "Silicone for Plastics," so I can't comment other than to say that the materials properties of glass and acrylic are very different, so make an adhesive that adheres to both is not easy. Without good data and experience I would be hesitant to use it in a critical application.
Click to expand...

The adhesive you would be looking for would be a UV catalyzed polymer. Such is used for the assembly of "hybrid" tanks, either acrylic and glass, or hard PVC sheet and glass. They are guarded proprietary polymers at this time. Though I suspect with some diligent research, it could be figured out.
 
If done properly it can be used for non-structure Don't use it for a 14" height difference baffle but works great for most purposes. Silicone for an external overflow box is a very bad idea, but acceptable for an internal use.
 
Maybe it's a question of semantics?
it doesn't really matter whether it "binds" to the acrylic or just wedges it, so long as you are only using it to hold a baffle in place. That's why so many sumps are successful using acrylic baffles on glass $1 a gallon glass tanks. If someone were recommending it to hold weight, like an external overflow, then duh. No. But really, are people hanging overflows off the backs of their tanks by the grace of God and a bead of ge II? I wouldn't do that even if it bonded, I wouldn't do that with glass-to-glass. If someone thinks that caulk is going to hold like acrylic weld does, just changing terms prolly won't sort them out.

I would think there's a wide range of strengths. In my (internal) overflow I used the clear GE that everyone says is reef-safe but then I changed my mind and got this [momentive sealant] cause I liked the color. It was a night and day difference in sticking power, I would need a razor to remove the black stuff. Only been a few months but it feels quiet firmly "stuck" even though idk if it's bonded or not.
 
Hi all
Silicone will work fine to stick acrylic to something else, however like one of the other posters said it cant be used structurally for acrylic.

I just found this out by constructing an acrylic refugium with silicone "for plastics and acrylics"
Thank god I did a "pull on the corner test" the next morning.

I ended up having a local window company cut me 1/4" plate glass to make the tank.
 
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