Measurement of Static Contact Angles

Measurement of contact angles appears to be quite easy when first encountered, but this can be misleading and the accurate measurement of thermodynamically significant contact angles requires painstaking effort. If the substrate is not prepared properly, if very pure liquids are not used while forming drops and if some important practical issues during measurement, such as drop evaporation, the location of the needle in the drop, and 

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Direct measurement of static contact angle by video camera or goniometer... 

Regions of practically immobile states of a meniscus are shown in Fig. 25 by arrows on the pressure axis for solution concentration Co = 5 x 10 (curves 3) and 5 x 10 M (curves 4). This makes it possible to assess static values of contact angles. Because of small hysteresis (the regions shown by arrows are short) the mean value of static contact angle is equal to 40° for C = 5 X 10 M and 36° at 5 x 10 M. The calculated values are close to those measured using captive bubbles [45] and differential ellipsometry method [46] on quartz surface for the same solutions. 

Determination of Static Contact Angle 2.2.1 Basic Measurement and Techniques... 

TABLE 1. Dynamic and Static Contact Angle Measurements of Selected Experimental Agents... 

The wettability of a polymer film normally is determined by static contact angle measurements. The surface free energy (SE) of a polymer can be determined by wettability measurements with two different liquids. The dispersion force and polar contributions to SE, 7 d and 7 p respectively, are also calculated normally by using the Owens and Wendt, and Kaelble methods [146,147], The measurements of contact angles (CA) on a given solid surface is one of the most practical ways to obtain surface free energies. 

Static contact angle measurement of the sessile drop. The contact angle, 6C, is the angle formed by a liquid drop at the three-phase boundary where a liquid, a gas, and a solid intersect. It depends on the interfacial surface tensions between gas and liquid nGL, liquid and solid nLS, and gas and solid IIGS, as given by Young s6 equation of 1805 ... 

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