Polyurethane Adhesives

Polyurethane Glues include glues such as Gorilla Glue, Elmer's Ultimate Glue Polyurethane and Titebond Polyurethane Liquid Glue. Polyurethane glues were designed specifically for wood but may work well on other materials as well.

The information provided is general. Always refer to the use, safety and cleanup instructions included with the glue.

Safety

  • Work in well ventilated area
  • Keep acetone or denatured alcohol on hand for cleanup from hands
  • Keep from contact with skin.
  • Wear goggles

Pros

  • It is solvent free.
  • It is waterproof.
  • It has a twenty minute open working time which gives time to get things positioned properly and clamps or other holding mechanisms in place.
  • Because of its expansive properties it tends to work better than most glues for end-grain joints.
  • Slightly elastic.
  • It expands and gets "into" the wood as it sets so creates a very strong joint.

Cons

  • It is toxic to touch and ingest.
  • One surface must be slightly moistened for the glue to set. Polyurethane glues expand with moisture and can be extremely messy if not used carefully.
  • Polyurethane glues require pressure to adhere and so joints must be kept under pressure until the glue has set. Set time can run as long as 4 hours during which the joint must be kept under pressure.
  • More expensive when compared to other glue options.
  • It expands and foams as it sets so if used incorrectly can spill out beyond the allowable limits for a glue joint.
  • Slightly elastic.
  • Difficult to remove from hands once it dries.

Cleanup

  • Denatured Alcohol or other solvents will cleanup polyurethane glues.
  • Acetone will also work for cleanup.

Instructions for use

Each manufacturer's instructions for use are slightly different. These instructions are included for reference only. It takes very little polyurethane glue to make a strong joint. After the surfaces to be glued have been smoothed, take a damp (not wet) cloth and lighted dampen one of the surfaces being glued. Next spread a very small amount of the polyurethane glue on the other surface. A good way to spread the glue is to use an old credit card and holding one of the long ends hold light pressure on the card as you drag it across the glue to create a thin sheen of glue on the surface. Mate the two pieces together and apply pressure in accordance with the manufacture's recommendation - usually 2 to 4 hours.

It is very easy to use too much of a polyurethane glue so you may want to practice on scrap pieces of wood until you get a feel for the correct amount of glue to apply. Click on the link on the right to see an example of what happens when you have too much glue in the joint. You can see that the glue has foamed out beyond what is generally allowable under structure challenge specifications. It is very difficult to remove this foam without damaging the underlying surface.

Because these glues expand it is very important that the surface you are building on be non-porous. Otherwise, the glue from the joint may expand into the surface underneath and you will find your structure glued to the work surface. I have had the glue grip onto a plastic laminate surface I was working on and tear off a piece of the laminate when I picked up the structure. Taping a piece of wide clear shipping tape to the surface under the joint prevents this from happening.

These instructions are from my experience using Gorilla glue. As I browed websites looking for information on glues I noticed that some manufacturer's have a polyurethane glue that may not require moistening of one surface.