Contribution of the shear wave ultrasonic reflectometry to the stickiness measurements

Today, non-invasive quantification of the adhesion of a deposit to a surface is always a challenge and, unfortunately, few tools are available in this area. This is an obstacle, in several industrial processes, to the identification of conditions limiting the fouling and to the establishment of eco-efficient cleaning strategies. In this paper, a non-invasive ultrasonic technique was developed in the aim of characterizing the adhesion of viscoelastic fluids or solid deposited on a substrate. We adopted the idea that the more a deposit is difficult to clean the more adherent it is. From this point of view the value of the reflection coefficient of an ultrasonic shear wave informs us about the adhesion of the deposit on a surface. A large bibliography on the adhesion measurement is given. Then the principle of ultrasonic test is presented and cares required for the measurement of the reflection coefficient are widely discussed. The ultrasonic reflection coefficients obtained with different controlled samples covering a wide range of interfaces (liquid/substrate, solid/substrate) are presented and compared with other indicators of adhesion. All the data on various samples showed that the ultrasonic test is a tool to discriminate non-destructively a large range of interface quality, allowing ranking according to the adhesive strength.