Loop tack tests provide the means of assessing the most important and yet the hardest to measure property of pressure sensitive materials, the tack. The method allows the end user to compare the "initial grab" or "application tack" of different laminates and can be extremely useful to those working with automatic labeling equipment where this property is of particular importance. The loop tack value of a pressure sensitive material is the force required to separate, at a specified speed, a loop of material (adhesive outermost) which has been brought into contact with a specified area of a standard surface.
The procedure is to hold the two ends of the adhesive coated facing material strip and form the strip into a loop, adhesive surface outermost, by bringing the two ends together. Clamp the ends of the loop for a distance of 10mm into the top jaw of the tester leaving the loop hanging vertically downwards. The sides of the jaw should be protected from the adhesive coating. Clamp the glass plate in the lower jaw. Position the loop into contact with the glass plate at a speed of 300 mm per minute. When full contact over the glass plate has been achieved (25mm x 25mm) immediately reverse the direction of the machine and allow separation to take place at a speed of 300 mm per minute. Record the maximum force necessary to completely separate each loop from the glass plate. The strips should be 25mm wide and have a minimum length of 175mm in the machine direction.
Equipment Required
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