Evaluation of the Surface Energy of Solids Using Two-Component Mixtures of Test Liquids

Abstract

The design processes of composite materials require considering the surface energy of the phases. The choice of a series of test fluids to determine surface energy in the framework of the Zisman and Owens-Wendt models sometimes causes difficulties in the interaction of these fluids – dissolution or swelling of the substrate. The minimum number of test fluids is two, but more is used to increase accuracy. The use of mixed solvents allows to increase the number of experimental points, as well as to more accurately adjust the polarity of the medium, which is essential in determining the surface energy of substances that are unstable to the action of many solvents. The paper considered the possibility of using a mixture of a pair of test liquids that do not interact with the material and factors that may limit the accuracy of the determination. Also, on the example of stearic acid illustrates the process of determining surface energy by this method. Polypropylene and polycarbonate were chosen to determine the surface energy in the Owens-Wendt model. Test liquids used included water, ethylene glycol, dimethyl sulfoxide, ethanol, cyclohexane, glycerol and tetrahydrofuran. As a result, the use of a mixed solvent to determine the surface energy of polymers can increase the accuracy of the method by increasing the number of experimental points on the Owens-Wendt graph. Increase of the experimental points area, however, is limited to the points of individual solvents of the mixture, and the uncovered part of the graph needs to be corrected to reduce the error. It is shown that the use of only mixed solvents is inefficient due to the restriction of the zone of variability by the area between the coordinates of the individual solvents of the mixture. It has been shown that when determining the surface energy of materials that are not resistant to solvents, the accuracy can be increased by using mixed solvents, but this requires balancing the measurement range.

Aspects of Wetting of Hydrophobized Surfaces Textured by a Femtosecond Laser

“…The value of the water contact angle was measured by the sessile drop method. Water-ethanol mixtures at different concentrations were used to determine the critical surface tension [6]. To characterize the surface of the sample and determine the value of the contact angle, an optical microscope with a built-in Delta Optical HCDE-50 camera (China) and the corresponding ScopeTek View software (China) were used.…”