We are all familiar with sticking down flooring – it is part and parcel of daily life in the flooring industry.
Yes, there are products that do not require adhering to the floor, and there are some that only need a tackifier. There are even some that only adhere to the neighbouring piece of floor covering. But predominately, floor coverings get ‘stuck down.’
As installers (or, in my case, ex-installer), we all have our preferred adhesive, brand, application method, viscosity or even smell. But ultimately, we will always look for some key features when we use any adhesive – especially for the first time. How long does it take to become receptive? What is the initial grab like? And, most important of all, how well does it stick the flooring down? And why not? That is exactly what we need to do: stick the floor down so it will not be able to come up easily ever again.
Now, I remember going to jobs where we had to rip up the old floor and it being ‘stuck like the proverbial’, and the rip out would be an absolute nightmare. Equally, I remember times when the flooring was barely held in place, and you could remove it with minimal effort. It is this massive disparity that could make you ask the question – what was done differently? Many reasons could be attributed to this: late placement, wrong adhesive, wrong notch on the trowel, poor workmanship, moisture in the floor, faulty adhesive – the list goes on. However, one reason that’s rarely mentioned is the floor covering itself.
It is fair to say that flooring meant to be stuck to the floor is designed with this necessity in mind. But with new products and materials forever creeping onto the market, it has now become much more critical as an installer, and even more so as an adhesive manufacturer, to consider exactly what is being stuck to the floors.
It is commonplace for most adhesive manufacturers to test flooring with their adhesives. Usually, these tests are for peel and shear as these come with a clearly defined method and standard. But these tests are time consuming and cannot be undertaken ad hoc, or without specialist equipment – such as a tensile testing machine. These types of tests take 4-5 weeks, requiring multiple samples to be bonded and a mean average to be determined. And that relates to only one particular adhesive/flooring combination. Usually, we will test all applicable adhesives to ascertain the highest-performing ones.
As you can see, the process is lengthy and labour intensive. So, what are the alternatives to understanding how to stick a particular product to the floor – or, more accurately, what is the product’s potential ability to be adhered suitably?
The Dynes test is perhaps a lesser-known test, but it certainly is one way to determine how well a product could be adhered. Dynes testing, in very simple terms, measures the ability of the molecules of each product (in this case, the floor covering and the adhesive) to attract each other. This test provides a measurement, or ‘score’ – the lower the score, the more difficult the product is to adhere. This is referred to as surface energy. The score the product receives is generally put into three categories – low, medium and high surface energy.
This can be visualised with water droplets. Water droplets placed onto a low-surface-energy material (such as a freshly washed and polished car) will stay spherical, whereas if you placed them on a high-surface-energy surface (such as a very dirty car), the water droplets will spread or ‘wet-out.’ It is the wetting out that is critical to the bonding process.
High surface energy: These products are so strongly attracted to others that they pose no issues when it comes to being bonded. High surface energy materials have surface energy measurements of between 300 dynes/cm to 1000s of dynes/cm, and include many metals and glass products.
Medium surface energy: Somewhere between perfectly wet-out films and perfectly spherical droplets, we find medium surface energy. These are materials typically measured at between 36 dynes/cm up to 300 dynes/cm. Many engineered plastics have surface energies in this range, as do natural materials such as wood, stone or concrete.
Low surface energy: Low-surface-energy materials are quite happy the way they are and show very little ability to be bonded. Materials with surface energy below 36 dynes/cm are considered low surface energy. These include polyolefin plastics such as polypropylene and polyethylene, as well as “non-stick” surfaces such as polytetrafluorethylene (PTFE).
In a world where the acoustic properties of floor coverings are becoming increasingly relevant, we are seeing more products being introduced into the market that come with acoustic backings or are simply an acoustic underlay. And we have noticed that these backings and underlays can sometimes fall into the low-surface-energy category. This is when bonding the floor covering can become a bit more troublesome. Backings with low surface energy can often still provide a good level of shear resistance, but when it comes to peel resistance, this is usually quite low.
So, how do you tell if a product may be a bit more difficult to bond than usual? Initially, I would suggest you simply look at it and feel it. It would look very smooth and dense. The second thing to do would be to try it in a small area and see how it adheres. To test it correctly and comprehensively, you would need to send it to a laboratory, where they would use ‘contact angle measurement’ equipment, but there is a timelier way. Dyne pens are widely and readily available, and usually only measure low surface energy. They come as a set and contain pens from around 50 dynes down to 28 dynes. You simply use the pen on the product and if the ink of the line drawn starts to bead into droplets within a few seconds, you move down numerically until the drawn line remains a line – that gives you the score. A score of 36 or below means it is low surface energy and you may encounter some difficulties bonding the material.
Remember, there is a right way and a wrong way to adhere flooring, and knowing all the considerations is key to a successful installation. Choosing the correct adhesives and methods, and ensuring the correct conditions in which to install the flooring are very important to achieving high-quality installations. Better Results Through Knowledge.
