STUDY OF THE SELF-ADHESION HYSTERESIS OF A SILOXANE ELASTOMER USING THE JKR METHOD

The JKR method measures the adhesion between two spheres or a sphere a nd a plane surface, all materials being elastomers. We have used this technique to study the self-adhesion of a siloxane elastomer. Our resu lts demonstrate that there is a large difference of behavior (hysteres is) between the loading and unloading regimes when the soluble fractio n of the networks has been extracted. The unloading regime is then not described by the classical application of the JKR model. We believe t hat the work of adhesion measured during the unloading regime is not c onstant along the contact area but rather decreases from its center to ward its edges. This behavior may be the signature of the JKR pressure profile (compressive in the center of the contact area and tensile ne ar its edges) the sign and magnitude of which influence the formation of hydrogen bonds across the interface. A generalization of the JKR mo del that includes this feature is proposed and gives a good descriptio n of the experimental data.