Glueing Acrylic

[ImanCarrot]

What would you use to glue an acrylic lens to an acrylic cylinder? It's got to stand up to water pressure typical that a diver would experience.

I was thinking straight superglue. Would this work or are there better alternatives?

Any help appreciated!

[karl1]

I use M.E.K. (A.K.A. Methyl Ethyl Ketone) - this will soften the plastic of the two surfaces and cement them together; use it sparingly since it could also "fog" the lens surface. The term glue wouldn't apply here since both surfaces are softened by the solvent and bonded by the evaporation of the M.E.K.

[lovebugjunkie]

I use Weld-on 4, it is what the the place where I bought my acrylic from suggested.

http://www.ipscorp.com/industrial/acrylics.html

[gandalf1]

Super glue may not withstand water and soften,
I always use Di-Chloromethane which dissolves the surface and 'welds' the pieces together.
John.

[ImanCarrot]

Many thanks for the replies. I'll try the different methods on some scrap components and see what happens!

[Geof]

Originally Posted by ImanCarrot What would you use to glue an acrylic lens to an acrylic cylinder? It's got to stand up to water pressure typical that a diver would experience. I was thinking straight superglue. Would this work or are there better alternatives? Any help appreciated!

Will the cylinder be empty or full? In other words same pressure inside and out; that is what a diver experiences, the pressure differential across the interior and exterior of the diver is zero. It will be easy to glue something together to withstand this pressure differential.

[cam1]

Geof:
Perhaps I'm misunderstanding you (my cup of coffee is 1/2 full)
When the container is shut/sealed at atmospheric pressure, and then submersed there will be a pressure differential accross the walls directly proportial to the depth. This is no different than a submarine. I'm not sure as to what the maximum safe depth is for a diver.

regards

[ImanCarrot]

Nope, the internal pressure will be different. ie: air on the inside, 100m (or so) of water on the outside (whatever divers go down to). I had toyed with the idea of filling the cavity with an index matching oil and having a thinner front dome since liquid is (fairly) incompressible I woldn't need as thick a dome- here's a rough sketch of what I'm gonna glue/ cement.

Behind the cylinder is going to be a PCB, some circuitry and a housing for the power supply.

[cam1]

Hi:The presure adds up.....
at 100m the pressure = 9.91kN/m^3 X 100m
= 991kN/m^2 x 1m^2/ (1000mm)^2
= .991Mpa or 143.7 PSIg

regards

[Geof]

Originally Posted by cam1 Geof: Perhaps I'm misunderstanding you (my cup of coffee is 1/2 full)....

I was being obtuse; if you have seen some of my previous posts in reply to queries from Mr Carrot you will see we both take the micky a bit.

You are correct, seal the container and submerge it and you do get a pressure differential; that is if the container is rigid and strong enough to sustain the pressure.

Humans are very floppy containers and cannot sustain any differential so a diver breathes air at the same ambient pressure as the surrounding water so there is no differential.

The sealed container mimics a submarine with a pressure differential across the wall.

The oil-filled container, if it included a flexible membrane between the oil and the water, would mimic the human body with no pressure differential between inside and outside. In my not humble at all opinion this is the preferred method.

Just make sure the acrylic cylinder is CAST acrylic not extruded.

[bloefeld]

I would think hard about using PMMA in this application. Have you thought about perhaps using polycarbonate instead. It is much tougher over a wider temperature range. It is more difficult to bond and it is very hard to get an optically clear joint when you do bond them. However difficult and impossible are not the same thing.

I have some expertise in adhesion science and the key to getting good bond to acrylic (well actually anything) is good surface preparation. In your case it is important to make sure your two jointing surfaces are flat and square with each other. Mask off the area you do not intend to bond and sand the area you do want to bond with 80 or 100 grit sand-paper. Blow it down with clean, oil and water free air. I would suggest using one of those cans of cleaner for computers. They are very pure and will not put anything you don't want on the surfaces.

I use methylene chloride as the solvent for adhesion. Melt-Melt bonds are the strongest adhesive bonds you can get. Basically the MDC melts a bit of both surfaces, they flow together and when the solvent evaporates the two pieces become chemically identical.

If you do not want to use a chlorinated solvent (be really careful in handling it if you do) then the prior suggestion of MEK is an excellent alternative. MEK is rarely high purity though, so your joint may not look as pretty.

In either case, use one of those little polyethylene dispensers with a needle attached to apply the solvent. You only need a few drops to form a thin film to get the desired results

Do not use 'super-glue' for anything you are going to put into water. cyanoacrylites are great in anaerobic environments but they de-polymerize when exposed to moisture. In fact if you are not using it as loc-tite don't use it for anything.

The other glue alternative is two part methacrylate adhesives. The will cross-link to the two surfaces, but are not as good as a solvent-melt joint.

Hope this helps,

Cheers,

Bloefeld

[cam1]

Hi:
Geof, I missed the "interaction", my wife tells me I'm a bit too focused and that I miss the nuances.
Also came accross some Loctite products: any one tried this product?
I have a project coming up where we'll have to fabrcate some 12 X 16 ducting from 1/4 ploycarbonate.

cheers