Contact Angle Measurements and Surface Characterization Techniques

Contact Angle Measurements and Surface Characterization Techniques 

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D.Y. Kwok, A.W. Neumann, Contact Angle Measurements, in Surface Characterization Methods. Principles, Techniques and Applications. Surfactant Series no. 87, A.J. Milting, Ekl., Marcel Dekker (1999) chapter 2, p. 37-86. (Review, many practical hints, 191 refs.)... 

The methods widely used in characterizing the surface grafting onto films are UV, attenuated total reflection (ATR) IR, X-ray-photoelectric spectroscopy (ESCA), contact angle measurement and other techniques applicable to the characterization of the surface treatments of polymeric substances. 

Once the durability testing of the fuel cells is finalized, the internal components are then characterized. For diffusion layers, some of these characterization techniques include SEM to visualize surface changes, porosimetry measurements to analyze any changes in porosity within the DL and MPL, IGC (inverse gas chromatography) to identify relative humidity effects on the hydrophobic properties of the DLs, contact angle measurements to observe any changes in the hydrophobic/hydrophilic coatings of the DL, etc. [254,255]. 

In order to calculate polymer/filler interaction, or more exactly the reversible work of adhesion characterizing it, the surface tension of the polymer must also be known. This quantity is usually determined by contact angle measurements or occasionally the pendant drop method is used. The former method is based on the Young, Dupre and Eowkes equations (Eqs. 21,8, and 10), but the result is influenced by the surface quality of the substrate. Moreover, the surface (structure, orientation, density) of polymers usually differs from the bulk, which might bias the results. Accuracy of the technique maybe increased by using two or more liquids for the measurements. The use of the pendant drop method is limited due to technical problems (long time to reach equilibrium, stability of the polymer, evaluation problems etc.). Occasionally IGC is also used for the characterization of polymers [30]. 

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