Gluing together 2 pieces of transparent plexiglas

Hi,
I am trying to glue together 2 pieces of transparent plexiglas.
One of them is raw and the other one is painted with an acrylic paint.
The glue to be used needs to be completly transparent as I want to obtain an optic effect on the paint.

I have tried to use liquid PMMA (plexiglas) as a glue. It works but not everytime. The problem is that too often the liquid PMMA is dissolving part of the paint and the result is not consistent. Sometimes it works, sometimes it does not. Sometimes it builds up air bubles in between the 2 pieces.
How should I proceed with the liquid PMMA in order to be successful?
Should I apply any specific chemical on the paint before applying the liquid PMMA in order to avoid too much dissolution by the PMMA and at the same time allow for gluing the 2 pieces?
How much pressure should I apply on the 2 pieces?
I would like to use liquid PMMA. I know it should work somehow as I have talked to a desinger who is using the PMMA as a glue. He however did not want to reveal the exact process he used with the liquid PMMA.

I have also tried to use Acrifix 116 and Acrifix 192. The results were even worse than with liquid PMMA as the dissolution is more important.

is it possible to glue the parts first then mask and paint. im pretty sure most cements would dissolve the paint, but am by no means an expert in these materials.

another option might be too look at different joining methods. screws, pressfits, or some sort of mating 3rd part might do the trick.

if you have a pic of the parts, would likely be easier to give an appropriate reply.

R

I would go with a 2 sided tape. There is a 3M pressure sensitive adhesive that is designed to adhere to lenses. Its optically clear and holds very well. Its used in most all cell phones.

The one I am thinking of is 3M 8142. 8141 is the same but it is 1 mil thick and won’t hold if you have any texture on your acryllic.

Contact 3M and you should be able to get samples, or, at the very least, be able to buy some.

The problem might be the 2 pieces you’re adhering together would be too large.

Hope this helps.

Here’s a link for the 8142: http://multimedia.3m.com/mws/mediawebserver?66666UuZjcFSLXTtnxfyn8z6EVuQEcuZgVs6EVs6E666666--

Ermm… I never thought gluing a painted surface is a good idea at all, other than if it was powder coated or something.

That’s a good point Cow…the paint will give out and peel off before the glue/adhesive. I was thinking that the paint was on the back of the plexi…not as the adhesive surface…re-reading…that is the case.

I think …you should consult your paint supplier.

Colors with certain proporation of harder gives strong bonding between
paint & object…afterwards paste another piece.

so…find out suitable harder… mostly from same company to that of color.

ADD

Never glue painted things even packaging we may not print colors over the part we need to glue. Because paint or toner will not stick correct. Best to leave the place you want to be glue clear from paint.

Or you glue it first and then paint it. Or use masking tape over the area you want to glue.

Using the 3M adhesive I mentioned, you could always laminate a printed piece of PC. Similar to how would be done for membrane switch keypads.

Have some experience with plastics, but like a lot of folks here mentioned… talk to some painters or adhesive specialists…

I would also like to add Silicone Glue as something to try out as well… Double sided-tape, I’ve also used and works well, but with a lot of humidity, it may fail… believe me, I’ve seen it happen =)

Hardener+paint

glues or solvents are going to dissolve your paint, there is no paint i know of that can withstand every solvent, as paint itself is a pigment, suspended in a solvent. Use the water clear solvent, and you’ll need to put even pressure on the point of connection, to prevent any bubbles, or crazing, then I’d mask and paint the part that needs to be painted. You could do a little googling into acrylic fish tank manufacturing, maybe find one of those guys to call, as they are doing similar work like this all day long…

IPS Weld-on #4 for Plexiglas acrylic
also Loctite products are great.

I imagine you’ve already tried something by now but the next time you need to join two pieces of acrylic, get yourself some MEK (methyl ethyl ketone). It’s a clear fluid with the viscocity of water. I recommend getting a hold of a syringe with a thin gague needle to help you apply. It’s not necessary to sand the plastic but in your case of having the painted surface, you’ll want to sand it away with a little 400 grit. Just run the needle along the edge of the two pieces of plastic you want to join and the fluid should fill any voids. MEK is not an adhesive, it literally melts the plastic together giving you a clear bond. Just make sure to empty your syringe and let it air out or you’ll find the plunger will melt into the tubing after a short time. Also, be careful not to squirt any in your eye. MEK can also melt eyeballs. :open_mouth:

What about the Weld-On #4 and using a vacuum bag to get the air bubbles out?