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PROBE TACK TESTS AS A CHARACTERIZATION TOOL IN PRESSURE SENSITIVE-
ADHESIVES [2001]
Bernard Lestriez, Dr., Ecole Supérieure de Physique et Chimie, Paris, France
Hamed Lakrout, Dr., U.S. Naval Research Laboratory, Washington, D.C., U.S.
Arnaud Chiche, Mr., Ecole Supérieure de Physique et Chimie, Paris, France
Alexandra Roos, Ms., Ecole Supérieure de Physique et Chimie, Paris, France
Costantino Creton, Dr., Ecole Supérieure de Physique et Chimie, Paris, France
A variety of adhesion tests serving, different purposes have been developed in the PSA industry.
The fiat-punch test, also called probe tack test, is widely used to test the short-time, low-pressure
adhesion. This test has the advantage of applying a fairly uniform displacement (uniform stress field and strain rate) to the adhesive film over the whole surface of the probe, and for those soft systems where
failure involves the formation of cavities and fibrils, it facilitates the analysis of the process. A set of probe-tack curves obtained for different PSA's and varying experimental conditions are displayed on
Figure 1. The maximum nominal stress σmax, the maximum nominal strain εmax, and the adhesion
energy, Wadh, defined as the integral under the stress-strain curves, are the main relevant parameters to
characterises the performances of a PSA, and provide clues for the practical design of the molecular
structure of the polymeric material for a given application. However, for a more refined optimisation of
the properties, it is helpful to understand what really happens when testing the adhesive film and how its
molecular structure is involved. New developments in both instrumentation and interpretation of the
results have provided insights in the debonding mechanisms of soft adhesive layers. In particular the
breakdown of the debonding process in separate stages allows a better understanding of the role of the
molecular features of the adhesive and the coupling between the rheological properties of the adhesive
and the surface properties of the adherent. Some of these new concepts are reviewed here with the help
of experimental examples.
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