Following is a partial glossary to help explain some of the terms we use both before and after an installation problem.
Of course, we have all heard of plasticizer migration, a term used when plasticizers leave a flooring product and enter an adhesive, turning it into a soft, gooey mess with no holding power. A plasticizer is a product that is used to soften and provide flexibility in various flooring products such as vinyl sheet goods and vinyl backed carpet tile. Two examples of plasticizers are mineral oil and hydrocarbon oil. Plasticizers are also used in adhesive compositions since it may improves tack, and develops “legs.”
The word polymer is used extensively. A polymer is a compound used in the adhesive’s components. It can be natural rubber, styrene butadiene rubber (SBR) or neoprene.
Binder is another term not fully understood. A binder is the substance that holds the adhesive itself together. The adhesive actually gets its common name from the binder. Some common binders are rubber-resin, latex-resin and asphaltic cut back.
Resins are solid or semi-solid maternal. They are either natural or synthetic. Usually insoluble in water, their purpose is to improve adhesion, improve tack, “wetting” of substrate, and improve the film strength by stiffening the film. Some common resins are vinyl, acrylic, gum rosin, wood rosin and hydrocarbons.
Fillers are basically substances of a non adhesive property. Fillers are added to lower the cost and also improve characteristics. Fillers control viscosity and stiffen the film. Some fillers are clay, silica, carbon black and calcium carbonate.
Of course none of the adhesives would be worth much without additions such as thickeners, antioxidants, light, and heat stabilizers, and without preservative (to prevent bugs), surfactants for wetting and stability, and emulsifiers.
Now that you know how an adhesive is made, we can talk about some of the problems we see in the field: Balling-up: This condition results when adhesive cannot be troweled properly. Since wetting agents and other goodies are usually present in the formula, the most common reason for balling-up is a dusty substrate, or when an adhesive, from age, is losing stability. Adhesive failure: This is an occurrence where the adhesive fails to bond to the substrate or the back of the flooring product. If the failure is in the substrate, look for dampness, curing compound or a weak and dusty surface. If the failure is the flooring itself, it most likely means poor adhesive transfer due to a bad or wrong size trowel, or waiting too long to place your flooring, causing the adhesive to be skimmed over, preventing transfer. Also, an incorrect adhesive may have been used. Cohesive failure: This is failure within the adhesive itself. This condition is identified by seeing a separation, with adhesive bonding to the substrate and the back of the flooring. This can be caused by use of an improper trowel size, installing too soon into wet adhesive that hasn’t begun to firm up, or premature movement of the flooring product itself or even defective adhesive. Freeze-Thaw Stability: This problem is not all that it seems to be. For example, one adhesive may be protected to 10 degrees with 3 thaw free cycles. Another may be protected to 0 degrees with a different number of cycles. Sometimes the length of time in hours can affect the reliability of the adhesive, so protect your adhesive.
A point of interest is that the carpet adhesive standards committee may have standards within a year. Work on peel strength is being done by an outside lab at this point with manufacturers’ round-robin testing to commence shortly. Some standards that the adhesives will have to meet are: peel strength, stability in storage, sheer strength, ability to be retacked, freeze-thaw stability, viscosity, ability to be troweled, and usability. These will be covered by an ASTM protocol.