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The best glues for exterior door panels that withstands heat12/3/14
I have been using Dr a natational casual product and it has worked until now it is not bonding the way that I think it should the wood has been aclamated and glued in a warm environment and the last couple of glue ups the wood would break on joints with no wood breakage
Your posting has given me information about the glues. I was searching about it. Thanks for sharing.
The wintertime open joint problem is the result of having wood that is not at the same MC as its environment. Usually the wood is a bit too wet or the environment is a bit too dry. Oftentimes, the dry environment is the same as the customer will have, so increasing the shop humidity is often only going to postpone the problem until the customer gets the product. So, MC of the wood is the key.
If your shop Humidity is 30% RH, measured with a digital hygrometer ($30 at Radio Shack), then the MC the wood will be trying to attain is 6% MC. If the wood is wetter, such as 8% MC, it will shrink.
Shrinkage may not be a bad thing, but when gluing two pieces together, if a gap develops of greater than about 0.006", then glue joint strength suffers. The end grain loses moisture the fastest, so often the ends are where the gap exists and so we see joint failure at the ends.
So, check the MC and insist on pieces no wetter than 7.0%. And so that there is no size change between machining the surface to be glued and the application of pressure, the time between these two operations should be just a few minutes...so that the wood does not have time to change MC and shrink.
Along with this issue, in the wintertime, we also see the pressure, put on the joint with a hydraulic clamp, for example, squeezes out the extra glue, as is suppose to happen, but then the joint loosens just a bit and with no extra glue to fill the gap, there is a failure.
Dr Gene - The OP mentioned problems with exterior doors. While I feel I understand the proper MC for interior work, what about exterior doors where we have absolutely no control over the end use environment?
An exterior door is really a "tough situation" as one side is exposed to a fairly dry interior (6% EMC winter and 9% EMC summer), while the outside is exposed to 12% EMC average, summer or winter (unless there is a storm door, which would dry things a bit; or if there is direct rainfall, which would set things).
The outside environmental conditions for many locations throughout the USA are given in the following publication.
I do believe that the most advantageous procedure is to try and coat all six surfaces of the door with a good, effective vapor resistant coating (Note: this also means thick, as a good coating that is too thin does not work very well). This coating will buffer the climate differences and moisture differences from inside to outside.
One way that we control it is to use separate panels that way if there is failure the weather dose not reach the interior
We use resorcinol for exterior work. Good glue but doesn't solve the moisture problem. I will no longer make exterior doors. When I did I used two separate panels separated by a sheet of plastic. Don't know if that was a good idea or not but never had a failure.
Seems to me there are several variables that have not been taken into account. Like.. where (on the Map of the World) are you making these doors... and where are they intended to be used?
What type of wood are you using?
Are you "testing" the joints in the shop?
... And I'm really confused as to what, "Dr a natational casual product", kind of glue you are referring to.
Certainly, moisture content (I hate those abbreviations you dudes are using) has a lot to do with the wood expanding and contracting, as the climate changes from season to season, but a properly made door with floating panels should be able to handle this unless the wood used is unsuitable for the climate.
I do know that TiteBond makes a water resistant glue and that Polyurethane glues like Gorilla Glue work well too. The downside to the polyurethane is the foaming excretion that needs to be cleaned up after it cures.
On another note... if you are using flat panels you might try using a spline joint and pining it as well. Or tongue & groove also comes to mind.
Good luck from HotLanta
The OP (original poster) said "Dr, a national casual", but the correct name is "DR made by National Casein". It is a UF (urea formaldehyde) adhesive used primarily for laminating. Such an adhesive has outstanding "exterior use" properties, so the problem that the OP is having is related to the surface preparation and gluing procedures and not the adhesive itself. Changing adhesives will not sure the problem as it is not an adhesive issue. This is a KEY concept in this case.
With respect to the last posting, I do wonder if a floating panel is adequate construction for an exterior door. I would vote "No."
Note that all PUR adhesives (that is polyurethane) do not foam, so PURs would be a good choice.
They are floating panels . The are raised panels , and with they weather change it takes longer for it too cure and after I let it set for 48 hours or more without stress on it it seams to be holding properly