Surface Free Energy & Wettability
Precise characterization of solid material surfaces plays a vital role in research and product development in many industrial and academic areas. Wettability of the surface is important in processes such as painting and printing, and has been utilized in the study of cell—biomaterial interactions. Wettability can be studied by measuring contact angle of the substrate with known liquid(s), after which the surface free energy is calculated according to chosen theory.
It is possible to calculate critical surface tension or surface free energy for a solid by testing against a series of liquids and measuring the contact angles. This parameter quantifies the characteristics of the solid and indicates the intermolecular interactions between a liquid and a solid. The critical surface tension or the surface free energy obtained in this way can be regarded as the ‘surface tension’ of the solid substrate, which is a characteristic property of the solid in the same way as the surface tension is for a liquid.
Wettability and sorption properties of loose powders and pigments are typically measured by the powder wettability method using Sigma 700/701 force tensiometers. In this method, also the contact angle and surface free energy can be defined according to the Washburn theory. The powder wettability measurement is commonly utilized in many application segments for research and development, but also for quality control. Typical applications include pigment development for ink and paint industries, and powder formulation for pharmaceuticals and material development.