I want to glue an “SPen holder” that I printed in PLA, to my Silicone phone case for my Galaxy Fold 6 phone. Can someone recommend a glue or preparation that will allow this to adhere?
Thanks.
Mike
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This is a subject near and dear to my heart. I went through countless glues, epoxies and adhesives. Hopefully my efforts will help you from wasting time.
This was the only item where it created a bond between silicon(which is inherently impossible to glue to) and other plastics. The bond is more of a “weld” rather than glue in that the two materials are chemically melted and create a joining material that is stronger than the two combined. Strength tests that I performed had the surrounding material fail but the bond itself was intact, much how what a good metal weld would perform.
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E6000 sounds like it could be your boy, I use it for a lot of rubber/plastic bonding. Smells great too**
Try silicone glue. The used in bath and so. There are different colors to choose from.
Silicone does not like to stick anything once cured.
The common misconception is that this is also true for silicone on silicone…
Hence we trying to scrape off what we can before caulking around the bath tub again…
In reality though the curing is just REALLY slow as it is all sealed and smooth.
If you HAVE to glue silicone parts together or silicone to some other material you usually run into big troubles.
There is special glues that do work but they are also quite costly and won’t work on all types of silicone.
Especially those softer types won’t work well.
Here is some things that worked for me in the past:
-
Casting silicone
Silicone for casting things is available everywhere these days but you need the kind that STICKS.
There is two type, the release type - it comes of basically any mould with ease once cured.
The permanent type, similar to what you get in the hardware store.
Once mixed together it is a thick liquid but unlike the normal casting silicone it will bond to suitable surfaces and fully cures throughout within a few minutes to hours depending on the formulation. -
Hetpane and ‘shoe glue’
Glue does not stick to silicone and won’t bond with it either.
Cleaning the to be glued silicone surface area with Heptane works like an activator that allows the contact glue to bond.
The key is to apply it as thin as possible, contact glue from the spray gun works best to get a really thin layer.
Let fully evaporate, meaning it won’t smell any more - don’t worry about being less tacky on your fingers, it will bond to the other side just fine.
Do not stretch the silicone and use lots of pressure to get the parts together. -
Cheating…
3M VHB comes in many forms and types.
Stickers, tape, sheets and also in foam, clear, stretch and non-stretch.
If you check their range you can also find extra thin tape.
Basically just enough to hold the glue on it.
If you use this tape to get silicone onto a rigid surface it provides a good enough bond for most applications.
In past I used some rather nasty chemicals in order to bond thin sheets of cast silicone to other things.
I learned that with silicone nothing is really permanent unless you apply the silicone directly to it.
Solvents/activators change at least the surface of the silicone and with that the chemical properties.
Over time this layer degrades…
Heptane is less of a problem, still nasty though.
It works best on fully cured silicone that is well aged.
Silicone with silicone is still my favourite despite the downsides of never getting the exact type to match unless you used the stuff from the hardware store for all.
Don’t be shy to use 120 to 180 grit sandpaper on the silicone to roughen the surface a bit - needs good pressure and works best with running water.
Just make sure to properly clean the surface with alcohol and Heptane.
Last but not least WET USE non-silicone caulk…
In the plumbing department you find quite a few products of this kind, even more if you check stores dedicated to sealants and adhesives…
These polymer based products need oil not water for the smoothing…
Most of them state they are suitable for use on silicone leftovers.
Only downside is that for large area application the curing time is a total pain.
If no air gets to it it basically won’t cure, so only good for things that are breathable, like terracotta pot or such…
And there is this stuff used for windscreens and panes in the aeronautics industry.
This black goo bonds to literally anything, stays flexible and cures quickly even in the absence of air.
Ask a car fixing joint nicely if they could smear you a little bit of it onto a piece of silicone for you try 
The magic black goo for car panels I used to use here in the uk is sikaflex 527 or 529, 529 can be painted over or sikapower all made by sika, sikaflex is one part and sikapower is 2 part. They will stick almost anything together, though I haven’t tried them with silicone before.
Trying this…
Says to let it dry 24 hours…Been 10 minutes and it already feels like it will hold. Next problem will be to try applying it neatly…not one of my strong points.
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How much are they charging for it?
Let us know how it worked out and what the bond strength is once cured please.
So that other’s may benefit. Which glue did you end up using?
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