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what do I need to use to bond polymetal (dibond) sandwiched between two sheets of 1.5" HDU. about a 3.5 x 5.5 sign. Is pb240 or west system epoxy better? thanks
-------------------- Wayne Webb Webb Signworks Chipley, FL 850.638.9329 wayne@webbsignworks.com Posts: 7404 | From: Chipley,Florida,United States | Registered: Oct 1999
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Ive used the west epoxy to laminate 1/8" plexi to HDU...We just sanded the back of the plexi to give it mechanical adhesion. Been out in the east facing sun for a year now and no failure.
I don't see why aluminum should be any different
-------------------- Bob Stephens Skywatch Signs Zephyrhills, FL
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Wayne, The sandwich of such materials suggests that you might be going to hang this sign from an arbour (sp). If so, you will need to also sandwich large washers over the aluminum, as these aluminums will not take the constant abuse around the mount area. If mounting from the sides then it should be ok, providing that you use a large surface to mount with. Over a year ago I did a step by step for a top hang, if you should need to look at one. One other thing. I use a combo of the Gorilla glue and Silicone II in seperate patterns leaving a moisture and pressure chase out the bottom center of my sign. I am always afraid of sweat and freezing getting in there. Jack
-------------------- "Don't change horses in midstream, unless you spot one with longer legs" bronzeo oti Jack Davis 1410 Main St Joplin, MO 64801 www.imagemakerart.com jack@imagemakerart.com Posts: 1549 | From: Joplin, MO | Registered: Mar 2000
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I like Jack's idea of leaving a moisture vent at the bottom. Makes sense, especially for large panels where it would be impractical to get a 100% contact/coverage with the adhesive.
A word about West System - it scares me. I had a near disaster with it that was caused by using it over a painted surface. It ripped that paint right off the primer, nearly causing both sides of a DF carved HDU sign to fall off their backing sheet of MDO. (Both sides were about half pulled away when I caught it). My fault for painting the MDO first, bare MDO may not have failed, but the experience left me skiddish. That West is so hard and brittle it has no flexability at all to accomodate expansion.
We prefer PB-Bond these days, with manual abrasion of the surfaces, spread out over one entire surface with a notched trowel, then wet the opposite substrate. Another product that's easier to use is PL Polyurethane glue in a caulking tube. Goes on like Liquid Nails, but super strong, use less. That's where Jack's "vent" comes in handy.
[ May 07, 2003, 12:38 AM: Message edited by: Joe Rees ]
SONGPAINTER Original Sign Music by Sign People NOW AVAILABLE on CD and the proceeds go to Letterville's favorite charity! Click Here for Sound Clips! Posts: 1974 | From: Orleans, MA, Cape Cod, USA | Registered: Nov 1998
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Another good reason for Jack's vent is that it allows the adhesive to cure. Some people run a bead of adhesive all the way around the substrate. That traps air, which keeps the panels from contacting and it may prevent the adhesive on the inside from ever setting up.
I run a bead up one side, across the top and down the other side. This seals the top and sides to help stop moisture from getting in. I do not run any more horizontal beads. I then run several vertical beads or series of globs, leaving the bottom open to allow any moisture that may get in a way out and allowing air inside from the bottom to help cure the adhesive. If you lay your panel onto the background at the top first, holding the bottom slightly away and then letting it down, you are forcing any air bubbles out the bottom as you go along.
I also like to use bonding products that have some flex to accomodate the different expansion rates from various materials used. The polyurethane adhesives such as PL Premium are good all around products. Lexel, available at Ace Hardware and Lowe's is another. I use PL Premium quite often.
If you ever attach Limestone, Travertine or Marble to a background, do NOT use silicone. Use thinset (I prefer the flexible version), epoxy or something like PL Premium. The acetic acid in the silicone reacts with the Calcium carbonate in the stone and will eat it away, causing later failure. Silicone can be used on Granite with no problem.
One last comment on bonding to Aluminum popped into mind. If using PL Premium, make sure your Aluminum is primed with an etching primer and/or painted. The adhesive reacts with bare Aluminum in a similar fashion to silicone on Limestone. I learned that lesson through a very expensive failure. Product support at PL told me my problem arose from using unfinished Aluminum.
In my experience, silicone and epoxy can be applied to scuffed mill finish Aluminum but not PL Premium. This may apply to other urethane based adhesives as well. Check with the manufacturer with regards to any such cautions.
[ May 07, 2003, 12:59 AM: Message edited by: David Harding ]
-------------------- David Harding A Sign of Excellence Carrollton, TX Posts: 5084 | From: Carrollton, TX, USA | Registered: Nov 1998
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Wow David, thanks for bringing that to our attention. Especially the Polyurethane to bare aluminum part. Now if I can only remember it when that situation arises next.
SONGPAINTER Original Sign Music by Sign People NOW AVAILABLE on CD and the proceeds go to Letterville's favorite charity! Click Here for Sound Clips! Posts: 1974 | From: Orleans, MA, Cape Cod, USA | Registered: Nov 1998
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