Elastic Analysis of the Loop Tack Test for Pressure Sensitive Adhesives
Williams, NuRocha Lyn
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The loop tack test measures the tack (instant grip) of an adhesive. An analytical model of this test seems to be lacking and is the subject of this research. The strip is investigated using several mathematical formulations, and the solutions are obtained numerically. The loop is created from a flexible elastic strip that is bent into a teardrop shape, with its ends clamped together. The strip is tested in a cycle, in which the loop is first pushed onto the surface, compressing the adhesive. Then the loop is pulled up, and gradually debonds from the substrate. The loop is assumed to be nonlinearly elastic and inextensible. The mechanics of the loop tack test are studied in order to determine the impact of various factors on adhesive performance. These factors include the stiffness of the backing, the stiffness and thickness of the adhesive, the elongation of the adhesive before debonding, and the contact time. The relationship between the applied force and the vertical deflection of the loop's ends is determined, as well as that between the applied force and the contact length. Also, the maximum "pull - off" force needed to remove the substrate from the loop is obtained from the results. Shapes of the loop during the cycle are found. This research will increase understanding of the behavior of the adhesive and backing during the loop tack test. With the computer model that has been developed, any set of parameters and conditions can be analyzed, and improvements can be made in the test procedure.
- Masters Theses