Avoiding Problems by Understanding the Different Types of Adhesives
June 10, 2008
Teachers get frustrated too! We know that we have covered all the necessary information but our students did not do as well on their test as we expected. We decide that we have to say the same things again…but differently. Teachers know this. They also know that if students do not use the information they learned they forget what has been taught. The phase, “use it or lose it”, applies to knowledge and information as well as it applies to physical skills, e.g. learning a second language in high school, but never using it. So readers, here’s some news to use!
On a recent business trip to Chicago, I checked in at one of the nicer hotels in the area. As I walked into the elevator and placed my luggage on the floor, I noticed the cove base falling off the metal walls. My curiosity peaked so I took a closer look. I noticed that even though the adhesive used was on both the wall and the cove base, the acrylic-based adhesive never dried and properly cured to reach its maximum holding power. Both the metal and the cove base are non-porous materials. Didn’t the installer know that “wet applied” water based cove base adhesives don’t cure properly between two non-porous surfaces? This type of adhesive sets up and cures when the water in the adhesive evaporates or is absorbed by one of the adhered substrates. Understanding this concept is easy if you equate this to the fact that manufacturers package a water-based adhesive in a plastic container and put a lid on the pail. The adhesive in the pail stays “wet” and never sets up or cures.
In further observation of the failed cove base I noticed that the adhesive appeared dry at the top of the cove base but appeared “uncured” as I reached the middle and bottom section of the cove base application. At first the installer gets blamed for this installational problem. However, I later learned that the contractor was provided with all the materials for the job. In fact the private labeled adhesive was delivered with the cove base. Everything was going perfect. The materials worked well in all the hallways (an application over porous sheet rock that had been left unpainted at the bottom 3-4 inches), but not well in the elevators. Shame on the architect or the specifier. There was a tremendous disconnect between the manufacturer and the installer. The installer was not to blame; the industry was to blame for not making it clear enough that a water-based adhesive that is recommended to be “wet applied” will not give maximum bond results between two non-porous surfaces. Fortunately this problem was small, but it just looked bad!
Can you use a water based adhesive in this application? Yes, however the water based adhesive must be the type of adhesive that can be applied dry. This means that the adhesive can be allowed to lose all of its water but have the necessary tack to hold the flooring materials/accessories adequately. Pressure sensitive adhesives and water based contact cements are great examples of adhesives that can be “dry applied.” If an adhesive does not remain sticky or very tacky after it loses its water, then it should not be used between two non porous surfaces. These adhesives only can be considered if they remain sticky after losing its water.
Another adhesive option in this tough application would be a two-part reactive adhesive such as an epoxy or polyurethane. These adhesives cure internally once mixed and not though the evaporation of water in the adhesive. One more concern: one-part, moisture-cured polyurethane adhesives are not a good choice between two non-porous surfaces. These adhesives need water to properly cure. When moisture cured/one part polyurethane adhesives are packaged correctly they remain useable. When the container is opened they are exposed to water which begins the curing process. These adhesives need water to promote adhesion. Wet applied only water based adhesives need to lose their water to properly set up. Both are problematic when installing a non porous flooring material over a non porous surface/substrate such as metal. Great adhesives, but the wrong application.
Knowing the FULL applications and the various adhesive types in our “going green” industry will assure our industry maximum success. Satisfied customers are our best advertisements.