Adhesive for Exterior Doors
If your panels are splitting at the glued seams, and TB III fails around 120 degrees, you might consider the old Weldwood Plastic Resin Glue. It's approved for use in fire-rated doors that are tested at a 250 degree temperature rise. Those doors have to burn for as long as 90 minutes to pass the test.
A reminder about the glue - it has about a one year shelf life, so make sure your supplier can offer you a fresh batch.
From contributor B:
I recently spoke with Franklin techs about some 2+ year old TB3. They told me that as long as the glue wasn't gummy coming out of the jug, and it dried as you would expect, it was good.
I would look at adhesives like West System epoxy if the TB3 is failing. TB3 acts more like TB1 in terms of radio frequency drying. That is, you have to let the joint cool before it can be moved. Heat it again and it can be separated (theoretically anyway). TB2, on the other hand, crystallizes hard immediately upon the radio frequency drying. In hot house situations like the overheated door, TB2 might be the better choice. Or epoxy or other catalyst adhesives.
From contributor J:
I agree with contributor B. West System epoxy is the way to go. I worked in the Caribbean for a while making exterior doors out of Spanish cedar and mahogany. We used West System epoxy down there, mainly due to climate, etc. It worked great.
From contributor K:
Be aware that epoxy, too, weakens with heat, though up around 180 F. I would recommend checking with the formulator for specifics.
From Professor Gene Wengert, forum technical advisor:
I agree with contributor B too. Epoxy deteriorates with UV light, so make sure that you use it only on doors that will be painted.
From contributor I:
I like West Epoxy for my exterior glue joints. Make sure your topcoat provides UV protection. Other reasons for panel failure could be too tight a panel fit in the groove, or poor gluing technique. Could glue be creeping out to the panel and making it stick during the gluing process? This would prevent the panel from floating properly and be a definite candidate for failure.
From contributor O:
I'm curious why no one has any further interest in using plastic resin glue. It seems to be unaffected by heat or cold when set up. It does require special care when doing the glue-up, but don't they all?
From contributor K:
I would like to point out as well that epoxy does not adhere well to smooth surfaces. The glue lines should be sawn or sanded with 80 grit, especially with dense hardwoods. We use a lot of epoxy, but plastic resin is a good adhesive as well. The epoxy has the longest open time of any glue we use, and the best shelf life as well as being compatible with different fillers for varying purposes such as thickening, fairing, coloring, etc. It is also more tolerant of varying glue line thickness. The heat factor is not significant in most situations, but I mentioned it because of the storm door condition the poster alluded to. I doubt that the heat buildup there would approach the softening point of epoxy, but it's something to think about.
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