Bonding acrylic??

bnt83

bnt83

Final Approach
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Brian
The plan is to bond a new compass mount block (clear acrylic) to a new windshield and the Weld-On #16 acrylic cement that is recommended seems to introduce a bonded surface that is less than attractive on these scraps I have. Is there a magic process that makes a very clear bond? The hair line crazing looking stuff is concerning.

 
I think the hairline things are not as noticeable as the excess and the air bubbles.
Masking, and better bubble control?
 
Too much. Weld on is so thin, it only takes a drop. You can then run another drop along the outside edges (like a fillet weld) but again, just a tiny tiny amount. Those scratches you see may have already been there, the huge amount of adhesive is working like a magnifying lens
 
maybe talk to these guys about what you are trying to do: http://www.plasticareinc.com

They will want detailed info on the materials you are attempting to join. I took my parts to them...
 
Let'sgoflying! said:
I think the hairline things are not as noticeable as the excess and the air bubbles.
Masking, and better bubble control?
Click to expand...

The instructions at great lakes aero plastics say to paper masking tape within 1/32 of an inch around the block and it looks like applying a mass of the cement to get a good squeeze-out would really help bubbles issue. Rake the excess cement onto the paper masking.
 
Its looking like what I really need to get is Weld-On #40, which is a two part acrylic resin and not a solvent based cement. The IPS website shows #40 being used on aquariums where optics quality retention is desired.
 
bnt83 said:
The plan is to bond a new compass mount block (clear acrylic) to a new windshield and the Weld-On #16 acrylic cement that is recommended seems to introduce a bonded surface that is less than attractive on these scraps I have. Is there a magic process that makes a very clear bond? The hair line crazing looking stuff is concerning.

Click to expand...

Too thick. The best way to do these bonds is with a layer too thin to allow visible bubbles to form, and to minimize the size of the bubble that can be produced in curing. The best way on a project this size is with a cheap little air brush rig, you can use canned air if you don't have a compressor. It takes some practice to get it really right for an optical grade lamination, so get a bit more scrap to practice with. A good starting reference is an even 'spatter coat' with between 70%-80% coverage. Apply from the center or an edge, which ever works better with the material in hand (less flexible=edge, more=center) with your finger applying pressure start in the center then rolling out. The edges of the droplets meeting will leave a layer so thin that any bubbles that do remain will be measured in microns. That's the best way I found anyway.
 
This #16 is thickened syrup-like which begins to form a skin as soon as it comes out of the tube. It's supposed to be "gap filling" vs the watery #3 & #4 which seems a lot of aquarium builders use.

Im using a large glob on a different manufacture's scrap pieces Which don't seem to craze but the bubbles are still a problem.
 
bnt83 said:
This #16 is thickened syrup-like which begins to form a skin as soon as it comes out of the tube. It's supposed to be "gap filling" vs the watery #3 & #4 which seems a lot of aquarium builders use.

Im using a large glob on a different manufacture's scrap pieces Which don't seem to craze but the bubbles are still a problem.
Click to expand...

No, wrong stuff, you can dilute it with xylene though and still get a clear result. You don't want 'gap filling' properties because they are the same properties that create trapped air bubbles, and have the viscoty to prevent their easily pressed escape. You want the watery kind, and you want it as thin as possible. You have smooth, flexible, plastic pieces, you should have no significant gap to seal.

The thinner the glue in any lamination, the better.
 
Oh, when you're done gluing it to your windshield, wax around it really well to protect the glass from the vapors of the glue curing to prevent future crazing. A fan on it for an hour wouldn't hurt either.
 
Haven't done anything like that since A&P school, but, back then the key was to have a nice bubble free blob of cement to squeeze out and keep under pressure until cured.
 
So far the acetone came out the best but hopefully the two part Weldon #40 does better
 
The two-part Weld-On #40 should be here today, but I already dropped the plastic compass mount block and chipped it :mad2: Another $25 down the drain and once again waiting for parts.

That all being said I cut up the old windshield, some new acrylic and whatnot and can practice using this adhesive. Hopefully I'll have a handle on it when the compass mount block arrives.
 
I'll put up more details after I get these practice pieces glued tonight. Some magnets robbed from an old hard drive should hold everything in place while it cures.

 
Weldon #40 wasn't exactly the magic bullet either. It seems fine, crystal clear bonds with no crazing.... as long as none squeezed out between the two pieces and it contaminated the edges of a lap joint.

And my god the stuff stinks, kinda like super glue but much more volume.
 
What we used to do when building architectural models was put the two pieces in place dry, then use a brush to apply the solvent around the edges and let it be pulled in by capillary action. I don't know that this technique would work for that large a surface, but if you put the thin stuff in the middle to get most of the area then applied it around the edges to fill in the remainder???
 
I was told by an architect (model builder too) methylene chloride was the weapon of choice for this task when he was doing it (35 years ago).
 
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