Contact angle and surface energy

Contact angle measurement is a technique used to assess the wettability of a surface by measuring the angle between a liquid droplet and the surface. This angle is influenced by the surface energy of the solid and the surface tension of the liquid.

A low contact angle indicates a strong interaction between the liquid and the surface and a high contact angle low interaction between the two. A low contact angle is typically desired for coating applications to ensure good wettability (i.e. spreadability) of the coating on the surface. A high contact angle, on the other hand, is preferred for surfaces that are supposed to repel certain kinds of liquids (e.g. hydrophobic coatings).

By measuring the contact angle between a surface and multiple liquids you may calculate the surface energy of the substrate. Multiple theories exist for the calculation of surface energy, which is a numeric representation of the total energy of the surface. These include the Owens-Wendt-Rabel-Kaelble (OWRK)/Fowkes, Acid-base, Wu, Schultz, Zisman, and Equation of State methods.

Contact angle and surface energy are important parameters in the characterization of paints, coatings, printing inks, and the substrates they are applied on. Additionally, this technique can be used to assess the performance of protective or adhesion-promoting coatings and technologies.

The price includes three analyses with two liquids, typically water and diiodomethane, with a contact angle device equipped with surface correction.

Practically any liquid can be used as long as the liquid does not chemically react with the surface and the surface tension of the liquid is known. Additionally, almost any non-hazardous and flat material can be used as the substrate.