Contact angles and surface energetics

Recent progress in the correlation of contact angles with solid surface tensions are summarized. The measurements of meaningful contact angles in terms of surface energetics are also discussed. It is shown that the apparent controversy with respect to measurement and interpretation of contact angles are due to the fact that some (or all) of the assumptions made in all energetic approaches [7-14] are violated when contact angles are measured and processed. For a large number of polar and non-polar liquids on different solid surfaces, the values of gamma(1v) cos theta are shown to depend only on gamma(1v) and gamma(sv) when the appropriate experimental techniques and procedures are used. An equation which follows these experimental patterns and which allows the determination of solid surface tensions from contact angles is discussed.