Acrylic Body Lam

[sumphead]

...stab myself in the eye with an unsharpened pencil.

OK, Being an acrylic junkie I though I would build a body with a black cast acrylic 1/8" accent lam between a walnut core and curly maple top and bottom (think high figured carved top and back, walnut skunk stripe centered top and back between the bookmatchings. Maple neck walnut headplate).

On to the test lab: I first though since I make my own acrylic welding solvents surely I can make a resin/glue that will make cast acrylic stick to wood. I figured a mixture of a resin based solvent and a simplified wood glue (PVA) would initially react and solvents would break down the PVA and look somewhat like a spreadable lumpy butter. I also ASSUMED it would soften the acrylic enough to allow adhesion to the wood. So I went for it and sure enough I got a yellowed cottage cheese consistancy that was as easy to spead as a well placed slimy sneeze. And for the record, yes I wear a respirator while playing with chemicals and plastics. The test went very well and couldn't pull my test lams apart, but on a larger scale it was a worthless effort as I could pull my lams apart with about an estimated 15-20 lbs of pressure. Basically a short drop on a completed guitar would be disasterous.

Then I tried a 30 two part epoxy.....the acrylic literally laughed at the epoxy then walked to the fridge and helped itself to a beer.

Any Ideas to make this stick? CA maybe

Otherwise I am going to choke on a bullet.

Thanks in advance,

R-

[thegarehanman]

Is scuffing up the acrylic a possibility? If so, you could try some polyurethane glue(gorrila glue or simular).

peace,

russ

[sumphead]

I should have mentioned I scuffed the acrylic before the epoxy attempt. I hadn't given a lot of thought to Gorilla glue mainly because I assumed it would not dry clear or at least be visible in the seam, is this not the case?

Thanks for the promt reply,

R-

[thegarehanman]

I think you could clamp it enough to make the glue line very fine. Give it a go, what's the worst that can happen, you lose a piece of acrylic and wood? big woop

[RAI6]

How about drilling holes in the laminate, so that the glue will actually go from wood to wood?

[postal]

Except for epoxy type glues, glue needs material to adhere to, not just a blob of glue. The drilled holes may work with epoxy, but I wouldnt try it with any other glue.

Personally, I think I'd run a bunch of short 1/4 inch dowels through the lams, and use epoxy or your cottage cheese conconction to get a thin clear glue line. PITA to line up that many dowels, but would provide the strength you're looking for.

[Digideus]

I was thinking the same thing as I read this post. dowels would prevent the acrylic from moving and would secure it to the body laminates for sure.

How about CA though? I know Drak uses it for securing his tops so its plenty tough enough. Perhaps a layer of CA onto the Acrylic and then let that dry to create a barrier between the acrylic and wood, then try the lumpy butter method with dowels through the acrylic to prevent any movement once the glue has started to set?

Should be as tough as Mr.T

[davee5]

Will CA bond acrylic? Yes, in fact very very well. CA, as in cyanoacrylate, is basically meant for bonding acrylic based polymers. Unfortunatley you are probably going to have a few small issues that might be easily addressed if you use CA.

Cyanoacrylate is a humidity curing adhesive, it uses water in the air as a catalyst in the curing reaction. All commerically available CA's are made with an acid stabilizer which slows air curing, but the acid is dispersed and removed from acrylic solution by water via amine groups on the acid. Note that somehow, water mists will not work for this, it needs to be water vapor so do try to accelrate curing by dunking your guitar in the pool... not that you would.

Wood, though, contains a lot more water than plastic. So what happens when you apply excess CA and put it in proximity with a high humidity environment or substrate is it cures in the air around it, falls back to teh surface, and adheres itself in a white powdery substance commonly called bloom or blooming. I would expect that when gluing a large amount of plastic to wood that you are going to see some serious blooming around the edges of your plastic.

That said, many many bindings are applied with CA between wood and plastic (though usually celluloids, not acrylics) without too many adverse effects, and once the CA has fully cured you can sand off the bloom and your surface with be real nice and scuffed up until you buff it out to a high polish. Just expect it to look terrible when you first apply it, and also expect it to fill any pores on the wood around the bonding area, preventing stains from being applied. you may want to consider keeping the glue away from the edge if you plan on color staining the wood, just to make sure the CA doesn't seal the wood entirely to hinder finishing efforts.

Generally epoxies are lousy on plastics for adhesion. You can wor around this as someone else suggested by drilling tons of holes in the plastic and bonding wood to wood while the epoxy in the holes holds the acyrlic in place because it's mechanically fixed rather than bonded.

Acrylic adhesives, like the kind you seem to be making ar home, are generally considered plastic welders, for plastic to plastic only. They create chemical bonds by breaking down both plastics and linking the polymer chains between them. While wood could technically be calssified as an organic, non-crystalline polymer, it's a little too amorphous and stable to break down and bond the way acrylic does.

CA is probably your best solution, it can do a combination of chemical and mechanical bonding and penetrates well if you get the thin stuff. Oh, and ignore Digidues' suggestion about letting the CA cure on the plastic and THEN glueing it with PVA, it's about the worst thing you could do. That would alter and damage the plastic at the bonding site, without creating anything that PVA can bond to anyhow, and would generally destroy your nice polished surface. Just apply a layer of cyanoacrylate (not too heavy) to the acrylic (it won't soak in like wood will) and clamp it firmly to the wood. Wait a long time, like 1-2 days, for full cure and you should have no problems.

Still.... test this on scrap first, a confident as I am.

-Dave

Edited October 11, 2006 by davee5