Application of thin-layer wicking method for surface free energy determination

Abstract

The determination of solid surface free energy is still not a fully solved problem. There are several approaches to calculating the energy from the measured contact angles of probe liquids. Surface free energy changes accompany all processes occurring at a solid surface. Therefore, knowledge about these changes is very helpful for better understanding and prediction of their occurrences. In the case of a flat solid surface, contact angle measurement is a principal method for surface free energy determination, but many naturally occurring or artificial solids occur only as powders. In the case of such systems, the thin-layer wicking method, originally proposed by Giese, Constanzo and van Oss and further developed by Chibowski and Hołysz, is useful for determination of the surface free energy. The experimental methods for the determination of solid surface free energy bear some doubts, and the obtained results may be debatable. Nevertheless, even the determined relative changes in the energy shed light on the investigated process, helping in its handling. In this paper the theoretical fundamentals of the thin-layer wicking method as well as some practical guidelines are described. Moreover, literature data of the energy determination for some powdered solids and fabrics are reported.