I wanted to glue some Gemini letters to a piece of alumacore that was covered in vinyl. I used a 30 min. two part epoxy. I let this sit for two days. when we set the sign everything was fine. After about two hours in the sun the letters are falling off. I checked the bond of the letters before we left the shop. You could pick the sign up off the floor by the letters. (30"x120") The Epoxy seemed to be melting. Could there be a bond problem between the Vinyl and the Epoxy? I did lightly sand the areas that were to be glued. We have used Epoxy to mount letters to wood and drywall with no problems. What would you use to mount these. Thanks....
Posted by Robert Thomas (Member # 1356) on :
Robert, did the letters have studs?? I don't see mounting plastic letters without them, unless they are flat cut, then I would use silicon.
Posted by Bruce Bowers (Member # 892) on :
Robert,
It sounds as though you are having some kind of reaction between the epoxy and the vinyl background. The heat of the sun may be causing the vinyl to gas off and breaking the bond between the two.
I might suggest that you use a piece of VHB tape and silcone to mount the letters. I don't think that you will have the problems with silicone that you are having with the epoxy.
We have used this method before with good results. The VHB tape forms an excellent bond with the pads and the silicone offers excellent secondary adhesion to the background.
Have a great one!
Posted by John Deaton III (Member # 925) on :
What Bruce says is good advice. I apply a piece of the tape to the pad in the center, and silicone around it, then apply the letter. This way, you dont have to use masking tape or whatever to hold the letter in place. Works great.
Posted by VICTORGEORGIOU (Member # 474) on :
Robert, we had a similar problem with vinyl backed letters glued to a substrate. After a short time in service the adhesive would totally release from the vinyl. We did some in house tests with good results. We reworked the job with a different adhesive. The repair job failed the same way. After that we studded the letters. Never did figure out why the adhesive lets go from the vinyl. The letters did catch full morning summer sun. Vic G
Posted by Si Allen (Member # 420) on :
Basically it is because epoxy doesn't bond well to vinyl!
Posted by Robert Davis (Member # 1641) on :
Thanks guys, I will get some VHB and Silicone today...
Posted by Ernie&DianeBalch (Member # 1301) on :
What is VHB and where do you get it?
Diane Balch
Posted by Steve Burke (Member # 2674) on :
VHB is a name that originally (and still does) denote a series of Very High Bond tapes made by 3M. It is a trademark but the phrase has become the KLEENEX catch-all of the adhesive tape world. It is basically foam tape or adhesive that has an extremely high grip- They sell many types, depending on substrate selection, indoor/outdoor app, etc...did you know 3M makes adhesive tape that can hold wings onto a jumbo jet?
Posted by cheryl nordby (Member # 1100) on :
This same situation happened to me quite some time ago except on plexi. It might have something to do with when you moved the sign it bowed just a tad? And broke the bond. I never use anything but silicone now. Clear.
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