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A dyne test is a method of evaluating materials to ensure surfaces are prepared to support adhesion. Dyne tests measure force to determine the surface energy of a material, which helps us select the glue best suited to a specific substrate. This test is performed on substrates using dyne pens that contain an ink that beads to indicate the material’s level of surface energy. Glue must be able to wet the surface of a substrate or it will result in poor bonding. When glue is applied to a substrate, its degree of wetting, or wettability, is significantly impacted by its own surface energy and that of the substrate. For wetting to occur, the surface tension of the glue needs to be lower than the surface energy of the substrate. Measuring dyne levels helps identify problematic materials with very low surface tensions and apply an ideal fix.

Glue-up tests are procedures that reveal the bonding capability of glues to substrates and help determine the setting speed of materials. This test is performed by cutting each substrate into small sections to apply glue to perform drawdowns. A drawdown board and Mayer rod are used to ensure an even glue application, and a four-inch speedball roller is pressed onto the surface with medium pressure. After standing at room temperature for 24 hours, the bonds are tested by pulling the substrates apart and evaluating the condition of the materials. A successful bond occurs when failure in the form of a fiber tear is apparent on one of the substrates, which indicates a complete permanent mechanical bond has formed. If no fiber tear is detected, the substrates are said to be held together by a suction bond, which is a much weaker bond. Suction bonds are not permanent and are likely to negatively affect product performance.

Heat and humidity tests are conducted to help measure the amount of curl between the glue and a substrate or determine how well a bond will hold under extreme conditions. After substrates have bonded together, they are placed in a humidity chamber at the desired temperature and humidity. Typical testing temperatures range from room temperature to 120°F, but can be higher depending on the glue, and humidity can reach 100% if need be. A typical time frame for testing is 24 hours. The substrates are then removed from the chamber and the bond is immediately evaluated.

A force test is used to determine the amount of force needed to separate bonded substrates once they have been glued together. Tests are measured in pound-forces or newtons by attaching a spring scale to one of the substrates and slowly applying a pulling force until the two surfaces separate.

A freezer test is used to determine how well a bond will hold up under freezing temperatures. This is an especially important test for determining the most effective adhesive for food packages that will be stored in the freezer. Samples are placed in our freezer at the desired freezing temperature for a set amount of time. Temperatures can reach as low as -40°F. The samples are then removed, and the bond is immediately tested for flexibility, strength and other important properties.