Contact angle Owens-Wendt theory

Problem 6.2 Characterization of a PVC surface with the Owens-Wendt theory The contact angles of water and methylene iodide have been measured on a PVC (poly(vinyl chloride)) surface to be equal to 87° and 36°, respectively. The surface tension of water is at 25 °C equal to 72.8 with a dispersion part equal to 21.8. For methylene iodide, the surface tension is 50.8, and the dispersion part is 49.5. All surface tension values are in mN m. Assuming the validity of the Owens-W endt theory, calculate the surface tensions (total, dispersion and specific) of the sohd PVC surface and comment briefly on the results. 

Calculate the specific contributions to the solid surface tension based on the Owens-Wendt theory and then compute the contact angle of water on these polymers using the OW theory. Compare the results to the experimental data. 

In a large part of the (current) literature the Lifshitz-van der Waals component (o, is simply termed dispersion component and the Lewis acid-base interactions (o ) are interpreted as polar interactions even though the material s dipole moments may be zero or the interactions originating from permanent dipoles are very small and can be easily associated with the dispersion part [6]. The misleading denominations go back to a historical misidentification of the acid-base interactions as polar interactions in the Owens-Wendt-Rabel-Kaelble [7-9] approach to calculate the IFT [6] (OWRK model). However, as an impact on the SFE calculation by this misinterpretation of this old theory occurs only when a monopolar base interacts with a monopolar acid, this nomenclature is still widely used. And here in this work we will also use the terms dispersion and po/ar interactions to differentiate the two major contributions to SFE, ST, and IFT. For a detailed discussion of the use of contact angles in determining SFE of solids and other methods of determining SFE, see Etzler [10]. 

To do so, we must perform contact angle measurements for different liquids on the same solid. The minimum number of required data depends on the theory. In the case of Owens-Wendt we need data for two liquids on the same solid, while the most advanced theories (Hansen/Beerbower and van Oss-Good) require data for at least three liquids on the same solid. Graphical methods can also be used, e.g. the Owens-Wendt equation can be written in the form ... 

Table 15.3 Components of surface tension for various solids (polymers) from the Owens-Wendt (OW) theory and the Zisman plot (critical surface tension). All values are in mN m . When two values are mentioned it is because they are based on different experimental values for the contact angle...

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