Polyurethane glue is type of adhesive used in a variety of commercial industries, as well as in hobbies and crafts. While it has been available in Europe for years, this type of glue is a relative newcomer to the U.S. market. In fact, the first polyurethane glue product wasn’t readily available in the U.S. until the early 1990s. Today, it may be found in most hardware supply stores and is commonly recognized by the trade names Excel™ and Gorilla Glue™.
Although this adhesive bears the descriptive term “polyurethane,” it has little in common with like-named finishes. However, some polyurethane glue formulations can perform as a sealant. For instance, the gel form is the type frequently used in boat and light aircraft building and repair. Other polyurethane adhesive uses include woodworking, metalwork, and masonry. Construction grade polyurethane adhesives can be used with composite decking, flooring, and concrete.
There are several advantages to using polyurethane glue over other adhesives. For one thing, it is suitable for indoor or outdoor use and is highly durable. In fact, some brands of polyurethane adhesives guarantee the bond to last as long as the materials that are being joined together. In addition, unlike many other adhesives of this type, it is applied straight from the container and doesn’t need to be mixed. Most varieties of polyurethane glue can be painted too.
The strong adhesive factor from this glue stems from its foaming action when it comes into contact with moisture, meaning that it expands as it cures. This also suggests that a light misting of water on one surface to be glued may be necessary, unless the material already contains a small percentage of water vapor (i.e., wood, stone, etc.). Since the glue foams, there is a temptation to wipe or dab the glue as it cures, but this is actually counterproductive. In fact, any excess glue is easier to remove by sanding or scraping after it has cured. In addition, only a small amount of glue is needed and should only be applied to one surface.
Like other glues, polyurethane glue has a limited shelf life, generally six months to one year. However, it will last longer if refrigerated. It’s also worth remembering that since this type of glue reacts with moisture, it will also react to the moisture on skin. Therefore, it’s a good idea to wear gloves when working with it.
One more safety caveat: Polyurethane glue should be kept out of reach of pets and children. As with skin, the moisture-activating properties of this glue means that it can swell and cause intestinal blockage if ingested.