Viscous dissipative energy density as a general adhesion characteristic of adhesive tape

The strength of adhesive tapes is generally evaluated using a peel or probe-tack test. However, these tests strongly depend on sample geometry considering the tape thickness of the backing film and pressure sensitive adhesive (PSA) layer. In this study, we propose the viscous dissipative energy density as a new parameter for evaluation, which is equivalent to the adhesion energy divided by the maximum elongation of the PSA layer during separation. Rubber-based adhesive tapes of different styrene contents were prepared, and their adhesion performance was evaluated based on the proposed parameter. Peel and probe-tack tests using tapes of various thicknesses were conducted with in situ observation using a high-speed camera. In the peel test, the adhesion energy can be obtained by converting the peel force using the tape width and peel angle; in the probe-tack test, it can be obtained by integrating the force divided by the contact area and elongation of the PSA layer. The adhesion energy divided by the maximum elongation from the probe-tack test showed an identical linear relationship with the strain rate of the PSA layer on a logarithmic scale, independent of the tape thickness. This relationship obtained from the peel test was slightly higher with more scattering. This is because the elongation of the PSA layer was distributed along the curved backing film, whereas it was almost uniform under the probe-tack test. Therefore, we confirmed that the viscous dissipative energy density can be used effectively as a material parameter, particularly when obtained from the probe-tack test.