Ridged Foam Board Adhesive

[RunnerDuck]

I'm using ridged foam board for the insulation in my walls and I'd like to know if anyone has used Loctite PL with ridged foam board.

In particular, what I'm using is "Foamular 250" from Owens Corning. It is made from "Polystyrene" and the instructions on the PL adhesive says not to use it on "Polystyrene bath tub surrounds, Polyethylene or for polypropylene applications requiring water immersion."

It also says "Adheres To: Foam Insulation."

This is not a "wataer immersion" application so I'd think it should work.

I've glued up a small sample and I've seen no adverse effects although it has not thoroughly cured yet.

Any thoughts or experiences you'd like to share?

Thanks,

[Padilen]

I'm using liquid nails construction adhesive, safe for ridged insulation.

[RunnerDuck]

Thank you but I decided to go with Titebond just in case. Since it doesn't really need a lot of structural adhesive to hold them in place it should work fine.

[KCStudly]

I've used PL300 which is specifically intended for foam board. It is very much like caulk.

The biggest issue with moisture and air cured adhesives with the foam board is that they seal themselves shut and prevent large areas from curing quickly, if at all.

For foam to wood the TB works okay as long as you spread it very thin and evenly. The wood has to be able to absorb all of the moisture from the glue. If you have a heavy brush stroke, pooling, or even just a thick application it won't soak up before it skins over and seals itself from fully curing.

Moisture cured PU's have the same problem; the foam keeps atmospheric moisture from getting in and if you mist it you might be adding too much moisture that can't escape.

I also ran into some trouble with the PL300. The instructions for hanging wall board said to run 1/4 inch beads about 12 inches apart to hold the foam up until the finished wall panels were fastened over, implying that it would be the panel fasteners that ultimately held it in place. I was trying to laminate two layers of 3/4 thk foam on my back hatch, so I decided to use a notched trowel, trying to get more of a structural bond and less bulging than you would see from a thicker bead. At first it only worked where I had kerfed the foam to let it bend, but not on the flatter panels that I hadn't kerfed. The kerfs had acted like air ducts. So when I reworked the piece that didn't adhere I added a bunch of shallow kerfs just to let the air circulate. Later I sealed the ends of the kerfs up, figuring that the trapped air channels would be just about as effective as the insulation. After all, that is what the insulation is for, to trap air and keep it from migrating.

I figure that the PL300 works per the instructions because the big beads actually leave a gap between the panels and the 12 inch separation of the beads allows plenty of air between beads. Since I was cutting out wire grooves, license plate and taillight recesses I didn't want any loose edges in between glue gaps.

[RunnerDuck]

Thank you KC, good information. I think I'll use the PL300 one the roof and galley hatch!