The success or failure of any adhesive installation depends on the adhesive’s ability to adhere to both the substrate and the material being installed, as well as on its internal strength characteristics.

An adhesive installation failure means that the adhesive does not have the ability to adequately bond, due to a lacking or weakness in one of two areas. Wetting is the adhesive’s ability, by water or other liquid, to wet the floor and the backing of the floor covering material. The other area is chemical; specifically, the ability of the adhesive to want to adhere, just as the opposite poles of a magnet attract.

The strength of an adhesive system is determined by the adhesion and cohesion properties of the adhesive itself. Adhesion bonds the surfaces of two substances together. The strength of this bond is known as adhesive strength. Cohesion, or cohesive strength, is the strength of the adhesive itself, which can be stronger or weaker than the bond.

There are four forces that can be responsible for an adhesive assembly breaking or failing. Before packaging their products for sale, adhesive manufacturers run quality control tests to be sure that they can satisfactorily resist them.

  • Tensile strength is the resistance of an adhesive to forces perpendicular to the bond line, i.e. a pulling action.
  • Shear strength is responsible for different parts of the assembly to slip or slide, relative to each other, in a direction parallel to their plane of contact.
  • Peel strength is the resistance to a load applied progressively to one edge of a flexible substrate. The force is usually applied at an angle greater than 90 degrees to the bond line.
  • Cleavage is the action or splitting at the adhesive line that results when a tensile or peeling force is applied to the bonding at one edge of the two rigid surfaces being adhered.

    There are three human factors that are common causes of bond failure. The most common is choosing the incorrect adhesive for the job. Improper surface preparation, due to inexperience or carelessness, also contributes to a high percentage of failures, as does the improper application of the adhesive.

    Let’s look a little closer.

    Do you read the label on the adhesive container to determine the recommended trowel notch size for the carpet backing you are installing? Are you, or your crews, spreading too large an area before making the carpet/adhesive assembly? Are you taking the temperature and humidity in the room into consideration?

    Do you use a seam sealer on all “glue-down” jobs? Do you roll with the specified weight roller? Do you re-notch your trowels during the day to assure consistent coverage? Do you use fresh adhesive on a job, or do you try to make a little more money by using two or three partial pails, and the pails are from a variety of manufacturers?

    Do you pull back the carpet and check for transfer of the adhesive to the back of the carpet? Remember, in order to achieve 100% coverage, 50% of the adhesive should transfer to the back of the carpet, and 50% should remain on the floor.

    It’s your reputation at stake when you don’t follow the Best Job Practices.