Rheology adhesive energy

A similar observation could be made for the adhesive energy. The adhesive energy must be intrinsically constant, independent of any experimental parameters, as seen in the case of PDMS10. However, results for PDMS3 showed a small variation and those for HR showed a large variation. This is, of course, due to the failure of JKR analysis, but we suspect that these variations contain fruitful information about nanometer-scale rheological phenomena. 

Fig. 13. Correlation in time scale dependence between adhesion and linear rheology, a) Adhesion energy (blue points) and peak adhesive force (red points) as a function of separation velocity for a polymer gel with an equilibrium modulus of 470 Pa b) tan(6) as a function of oscillation frequency.

Based on the arguments presented thus far, it would seem that, for a given PSA, the work of adhesion, and thus the peel force, should decrease systematically as the surface energy of the release coating is decreased. Therefore, fluorochemical containing polymers should provide the lowest release forces. In practice, these generalities often do not hold, due to other factors, such as interfacial dynamics and rheological considerations. 

Adhesion results from the combination of an adequate surface energy couple between the PSA and skin and rheological properties. Adhesion is commonly measured by a peeling test, which involves the measruement of the force required to peel an adhesive, spread on to a flexible backing, from a substrate whose surface properties are well characterised. 

This relates the test result (the measured peel load F) to a measure of intermolecular forces (the work of adhesion Wa or of cohesion Wc, see Wetting and spreading) and to the rheology via various terms such as energy dissipated in plastic deformation lApiast, in viscoelastic loss iAv/e, in bending Abend, and so on. Here, b is the width of the peeled strip. 

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