They usually have no idea that there are a lot of additional costs involved with an installation using an epoxy adhesive. Not only is an epoxy adhesive often much more expensive than the acrylic or latex adhesive, but installation is a lot more labor-intensive. Plus, there are only a few installers that fully understand the product’s characteristics and how to work with it.
What is an epoxy adhesive? Epoxy adhesive is a two-component, chemically set, hard-setting thermoplastic adhesive made of two components (resins and hardeners) and is 100% solids. A 100% solids adhesive is a non-shrinking product that has little to no tack, and turns from a liquid to a solid in a period of time depending on temperature and mix ratio.
Thermoplastic adhesives are very temperature-sensitive and will set much faster in warm conditions. With thermoplastic adhesives, proper jobsite conditions are a must. The warmer the substrate and ambient air temperatures, the faster the epoxy will develop. Any time the jobsite conditions are cold it requires more time for the installer to watch over the adhesive, which involves rolling the material with a heavy roller multiple times until the adhesive sets. Depending upon the epoxy, a jobsite temperature at 55°F (12.8°C) can mean a properly mixed epoxy can add an additional 3 to 6 hours before the adhesive sets to a point it will hold the material.
Mixing. Mixing an epoxy adhesive is often where a problem begins. The adhesive comes in two containers: part A and part B. Manufacturers of the epoxy adhesives place a specific amount of either the resin and hardener component into each container. Often one container will hold a larger quantity of adhesive than the other. The reason is each epoxy is designed for specific bonding performance for specific types of materials and/or conditions. That is why a resilient flooring manufacturer may have more than one epoxy for their product mix.
To properly mix an epoxy it is necessary to remove the entire contents from one container into the contents of the other container. Neverattempt to mix an epoxy on the floor. Doing so may result in a spot where the substrate has absorbed the first component and fills all of the pours before the second component can be added. This can result in a bubble due to the lack of bond due to improper mixing.
In the process of mixing, it is necessary to clean the one container out completely. For metal containers it works best to cut the bottom out of the container because it makes cleanout much easier and the amount used is more precise.
Once the second component is placed into the other container, the two should be mixed with the wood paddle, with an up-and-down stirring motion. This will pull the adhesive off from the bottom of the container to mix with the adhesive that was placed into the top of the container. You should continue this stirring motion until the adhesive is mixed into a uniform consistency.
Some installers will use a drill motor with a paddle to mix the two components together. I discourage this action for two reasons. A high RPM will tend to whip air into the mix, creating a possibility of trapped air, which could create small bubbles. Also, power mixing can create additional heat from the fast movement and friction, which will cause the epoxy to set faster than normal making the adhesive thicker and more difficult to spread. This acceleration of the set of the adhesive is more likely to develop bubble problems later in the installation.
The mixed epoxy needs to be removed from the container as soon as possible. The longer it stays in the container the more the epoxy will heat up and accelerate the development. It’s best to get it out onto the floor and in as thin a mass as possible; this will keep the adhesive from getting warm and thickening up.
Application. Epoxy adhesives need to have a surface that can allow for a good mechanical bond. This means no residues on the surface of the substrate. Residues can fill the pours and capillaries of the surface of the substrate. Concrete should be free of any sealers or curing compounds and not have a hard-trowel (shiny) finish. All of these prevent the adhesives from attaining a good mechanical bond.
Next is the trowel. When working with epoxies, you should start with a new trowel that matches the specifications set forth by the manufacturer of the epoxy. Too much or too little adhesive can cause major problems.
Spreading the adhesive for Luxury Vinyl Tile (LVT) or tile that requires epoxy is generally easier to install using a wet-lay method. This requires the epoxy to be spread given a prescribed open time, then the tile is placed into the adhesive and rolled immediately. Normally, the installer will work off the tile to prevent slippage of the tile. With sheet material, the application of the epoxy is more critical.
Placement of sheet material into the epoxy. After the prescribed open time, unroll or carefully place the sheet material into the adhesive. The object is to keep air entrapment at a minimum. Air trapped beneath a sheet material is difficult to remove and will compress.
As the epoxy adhesive develops, the compressed air will slowly force the material out of the epoxy, forming a bubble. If the bubble is not found before the epoxy sets, it will result in a permanent bubble. For a long time it was thought the epoxy was off-gassing, but that is not the case. Avoid getting on the sheet vinyl with your knees as that will displace the epoxy, leaving a void that will show-through as a bubble.
It is very easy to trap air beneath the sheet material and then end up with bubbles, and once the epoxy sets there is no way to completely correct this. There are several methods to eliminate this problem.
First is to back-roll the material so it can be un-rolled directly into the adhesive and keep air entrapment to a minimum. The epoxy then needs to be troweled on with all of the ridges running in one direction (combed). This will give any trapped air an avenue to escape. The second method is to trowel the epoxy, then back-roll the epoxy with a short-nap paint roller to knock down the trowel ridges, creating a uniform coating of the epoxy.
Rolling.The most important thing in the installation of anymaterial set with an epoxy is the process of thorough rolling, with the proper weighted roller. Rolling of the material is not a one-time-and-forget-it ordeal. Materials should be rolled in both directions immediately after the material is placed into the epoxy, then again in about an hour, and finally once more in about three hours.
On the final rolling be on the lookout for bubbles. If you find any bubbles take a pin (not a knife) and puncture a small hole along the edge of the bubble on a sharp angle to relieve the air pressure, followed by hand rolling with a steel hand roller to remove any additional trapped air.
Bubbles in sheet materials are a common problem when installed with an epoxy adhesive. With a few changes in mixing habits, installation techniques and a thorough immediate rolling of the material, installation with an epoxy can be accomplished, but it is still going to require a lot of time and attention to detail.