Gap control: Ultrabond ECO 307

Some of you may not have had the pleasure of walking on this earth for more than seven decades and had the chance to see trends come and go. I have, and I have seen a lot of change. Fashion has always been one of those things that changes quickly over time. I can recall fads like bell-bottom pants and platform shoes that were the “must-haves” during the disco days. Miniskirts and big hair followed along during that time frame if you recall, but there came a point when that fashion took things a little too far and clothing became less flamboyant and more subdued.

Technology also tends to take things a little too far sometimes in its effort to make your life easier, faster or more efficient. I can recall a time when I was promoting new technology in the floor-covering installation business that would make the application of floor-covering adhesive a lot faster, but it may have taken it a bit too far. It happened on a demonstration of this new technology in front of some important commercial flooring contractors. I had prepared and practiced my pitch for days prior to this demo, but when it came time to pull the trigger, something blocked the pump mechanism and the machine did not work. Scrambling to try solving the problem only made it worse when pressurized adhesive splattered all over me in front of 12 giggling installers. Feeling my pain, the foreman walked up behind me and simply said, “That never happens to my trowel.” At that point I knew he was right and that sometimes the old ways of doing things are the best ways of doing things.

My rambling point here is that maybe we have taken things a little too far in the realm of luxury vinyl tile (LVT) or luxury vinyl plank (LVP) installation based on methods that are faster, more efficient or easier. I say that because at the very beginning of LVT’s infancy, we installed a lot of it using hard-set, wet-set adhesives that required super dry concrete slabs, and the result was remarkable but expensive. It was remarkable in that the floors remained bonded, and gapping was hardly ever seen (and when it was seen, it was usually due to poor manufacturing processes). It was expensive in that it typically required the installation of an epoxy moisture-vapor barrier to get the surface of the substrate to those magical measurements of 3 lbs. (1.36 kg) MVER and 75% relative humidity. For those of us in the adhesive manufacturing world, this was a marketing and product development paradise.

Two big issues were voiced by the installation community: This wonderful flooring product took too long to install and required expensive moisture protection. With those opportunities in mind, the adhesive manufacturing community started to introduce adhesives that changed over time. These adhesives started off in a “pressure-sensitive mode” and then slowly toughened up to be more like those hard-set, wet-set adhesives. These phase-changing or “transitional” acrylic adhesives were very well received, as they gave the installer about two hours of sticky time to install LVT once the adhesive has been spread. But two hours of working time is still short if you are working in areas of 1,000 square feet (92.9 m²) or greater. Further, these adhesives were designed to provide a little more moisture resistance than previous formulations and installers could work on slabs with 8 to 10 lbs. (3.63 to 4.54 kg) MVER and 80% to 85% RH.

Again, another marketing and product development opportunity for the adhesive development community: Make adhesives that have greater working time and higher moisture resistance and, surely, we will get more buy-in from the installer group. That is exactly what happened. Super sticky, pressure-sensitive acrylics with high moisture resistance were introduced to the market, offering up to 12 hours of working time and suitable for use on slabs up to 99% RH. It was like a gold rush out there, and adhesive manufacturers had to scramble to keep up with demand. The sky was blue and the sun was shining, but there were clouds on the horizon foretelling of problems yet to come in this magical world. Those problems were gapping and peaking of LVT/P that, no matter what we tried to do, became a commonplace occurrence and a constant complaint from end users.

The one thing everyone seems to overlook is that LVT is a piece of plastic and as such is sensitive to temperature. When you install LVT on a 90ºF (32ºC) day in an unacclimated environment and it looks great when you leave, but a week later after the building owner moves and says that there are gaps all over his floor, you say, “That’s not possible! It was perfect when I left!” What happened is simple science. The LVT was installed warm and as such slightly larger than it would be at room temperature. The building owner took possession of the property and turned the HVAC on and brought everything down to 72ºF (22ºC). Not only did the air cool but so did the flooring. When the LVT cooled, it shrank back to its room-temperature dimensions and left gaps at every butt seam across the floor. This physical phenomenon is called the coefficient of thermal expansion. Every solid has this and, as you would suspect, different materials have different coefficient of expansion numbers. Flooring manufacturers know this about their products, which is why they always tell you to acclimate their product to the working temperature of the area and to maintain those temperatures for the life of the floor. What needs to be understood here is that LVT will change dimensions with changes in temperature.

What you also need to know – and this is very important – is that pressure-sensitive adhesives (PSAs) will move when the flooring moves. Pressure-sensitive adhesives are sensitive to pressure, hence the name. This means that when you put pressure on them, they move ever so slightly to get proper bond. The more pressure, the more they squish and the better the bond. The pressure, or force, resulting from the shrinking of the LVT will also cause the adhesive to slowly flow over time, allowing for gapping to occur. The opposite of gapping, called peaking, can occur when LVT is installed at room temperature and then exposed to high heat such as radiant-heat systems or UV radiation from big windows. This will warm up the LVT, causing it to expand as well as soften most PSAs and, when the LVT expands, it smashes up against the next piece to cause peaking.

The bottom line? This flooring type is only going to continue to grow in popularity based on its many attractive performance and installation features. But if you want to eliminate the gapping issue, you have a couple of choices.

The first choice is to put a lock box on the thermostat controlling the temperature of the environment such that it never changes from 72ºF (22ºC), ever. You will also have to protect LVT installations from direct exposure to UV radiation (sunlight through windows) to keep it from getting hot. You can stop laughing now: We fully know that this is not going to be a viable option and impossible to control or limit.

Our second choice is to use our trusty pressure-sensitive adhesive differently, and many manufacturers are now encouraging the installers to lay the flooring into these adhesives while they are still wet or semi-wet. This helps to improve coverage on the back of the flooring, reduce the thickness of the bond line, and enhance overall bond and shear performance. But these are still relatively soft and sticky adhesives that, no matter which method you use, will eventually give under the pressure of LVT shrinkage. When that happens, gaps or peaks will occur. So, what can we do?

The best solution for gap control for LVT, in this writer’s opinion, is to go back to the way we used to do it using hard-set, glass-like, wet-set adhesives. This is a tough pill to swallow as it is a step back in terms of speed and efficiency, but if you want an installation of LVT/LVP that is gap-free no matter what the end user dishes out, you might need to rethink how you approach these projects.

Those of us in the adhesive manufacturing community are listening and are working to bring you hard-set adhesives that are easy to work with and robust in today’s high-moisture-concrete conditions. That is exactly what MAPEI’s R&D group has done with the development of Ultrabond ECO 307 hard-setting adhesive for resilient flooring. With this new development, after listening to flooring manufacturers, contractors and installers, MAPEI has come up with a high-performance solution for LVT/LVP that solves a lot of problems. Ultrabond ECO 307 has been designed to provide phenomenal shear strength, rivaling the performance aspects of two-part reactive adhesives. It provides all this strength in a one-component, water-based formulation, and it works equally as well on high-moisture concrete slabs up to 99% RH. The only caveat here is that the concrete must be porous.

So, when it comes to doing things the old way, MAPEI can do that with a modern twist by adding high-moisture resistance to a wet-lay, hard-set adhesive.