SOLID-SURFACE FREE-ENERGY COMPONENTS DETERMINATION BY THE THIN-LAYER WICKING TECHNIQUE

A thin-layer wicking technique [1] and van Oss et al.'s [2] approach to interfacial free energy interactions were tested to determine the solid surface free energy components: apolar Lifshitz-van der Waals, gamma(s)LW; and polar, electron donor, gamma(s)-, and electron acceptor, gamma(s)+. For this purpose, the penetration rates of n-alkanes, diiodomethane, water, formamide, toluene and chloroform were measured. For these studies, silica, used for thin-layer chromatography, and alpha-Al2O3 were used as the model solids. It was found that both are strongly polar, electron donor solids with weak electron acceptor interactions. It is concluded that van Oss, Good et al.'s [2] approach to the interfacial free energy interactions and the thin-layer wicking technique are verv useful for explaining many interfacial phenomena taking place in the dispersed systems. However, more experimental work using different systems is needed.