Peel force time dependence

Tokumura, F., Ohyama, K., Fujisawa, H., Suzuki, M., and Nukatsuka, H., Time-dependent changes in dermal peeling force of adhesive tapes. Skin Res. Technol. 5, 1999, 33-36. 

Fig. 2. Dependence of peel force (g cm ) npon contact time h for poly isobutylenes of molecular weight (a) 100,000 g mol and (b) 150,000 g moD peeled from cellophane. Dots are expaimental points, hues are daived from Eqn. 1...

Figure 2.3. Dependence of the peeling force, p, on time, r, (see the text). [Adapted by permission from A. N. Kuksin, L. M. Sergeeva, and Y. S. Lipatov, J. Adhes., 6, 275 (1974)]...

Typical force versus time traces obtained from T-Peel tests are shown in Fig. 11. As can be seen, the peel load reaches a nearly constant value for both substrate materials, with some minor fluctuations superimposed on the results. These values have been used in an analytical model to calculate the adhesive facture energy, Gc [8]. For all the tests performed the crack propagated cohesively in the adhesive layer. The peel load was found to depend on the alloy type and on the thickness of the substrates, since most of the energy during the test is dissipated by plastic deformation of the arms. Numerical FV work is in progress. 

Another important property of PSAs is their tack or response to light pressure. Bringing a probe of known composition in contact with the adhesive with a specified force for a specified time and then measuring the amount of force necessary to remove the probe from the adhesive at a specified rate measures tack [38]. Peel strength and tack are dependent upon the rubber to resin ratio and are inversely dependent upon the cross-link density. Representative physical propertied of PSA tapes are provided in Table 27.5. 

Clearly, the peel strength is not a fundamental property for an adhesive. The value of force per unit width required to initiate or sustain peel is not only a function of the adhesive type, but also depends on the particular test method, rate of loading, thickness and stiffness of the adherend(s) and adhesive as well as other factors. Thus, peel tests generally do not yield results that may be used in quantitative design. This does not imply, however, that the peel test is not a useful test. Peel tests provide quantitative comparisons between different adhesive systems, insight into rate and temperature effects, etc. Additionally, peel tests can be used to provide fracture mechanics information as will be discussed in the next section. In the author s opinion, the latter aspect of peel tests has been perhaps most adroitly exploited by Gent and Hamed [18-20] who used peel tests in conjunction with fracture mechanics to obtain insights into time-temperature effects, the role of plasticity, and many other aspects of adhesive fracture. 

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