Evaluating uncertainty of surface free energy measurement by the van Oss-Chaudhury-Good method

Among the great number of methods for measuring the surface free energy of solids, all originate in contact angle measurements, which are carried out using various probe liquids, and employ certain relationships and assumptions. Contact angle measurement can be distorted by a number of factors that occur during the measurement and distort obtained values, and therefore must be accounted for. The present work describes the application of the van Oss-Chaudhury-Good approach in determining the surface free energy of aluminium sheets with the use of three probe liquids: water, diiodomethane and glycerol, with assumed values of the surface free energy components. The study employed direct measurement of the contact angle with the goniometer. Subsequently, measurement uncertainty with the van Oss-Chaudhury-Good method was evaluated, which revealed that the major source of uncertainty is the discrepancy between constant values describing properties of probe liquids.