Wetting solid surface tensions

Polymer Equilibrium Liquid Surface Tension Ref. Critical Surface Tension of Wetting Solid Surface Tension"" Ref... 

SOLID SURFACE TENSION (WETTING PROPERTIES OF SOLID SURFACES)... 

Contact angle — A measure of the ability of a liquid to wet solid surfaces. It expresses the relationship between the surface tension of a liquid and the surface energy of the surface on which the liquid rests. As the surface energy decreases, the contact angle increases. 

In this work, ordered arrays of core-shell particles were used as model surfaces to study the water wetting behaviour of these surfaces. Two factors were varied in the wetting experiments (i) the shell chemistry and hence the solid surface tension of the organic shell, and (ii) the height roughness from sub- xm up to xm roughness values whereas the Wenzel roughness factor was kept constant. 

Solid-liquid Wettability Sol, gel, colloidal suspension, solid emulsion, wetting, spreading, surface tension, friction, lubrication, diffusion, pervaporation, capillarity, electrochemistry, galvanic effects, corrosion, cleaning, filtration, ion electromigration, optical properties, charge transfer, nucleation and growth... 

Note (Tc is the critical surface tension of wetting, and a is the solid surface tension obtained in a manner similar to that of Owens and Wendt (7) but with a series of hydroxy-containing liquids rather than just water and methylene iodide. 

Surface tension studies of the most common fluorosilicone, poly(3,3,3-trifluoropropylmethylsiloxane) (PTFPMS), give unexpected results. Compared with (PDMS), PTFPMS has a higher liquid surface tension, a similar critical surface tension of wetting, and a considerably lower solid surface tension, as determined by water and methylene iodide contact angles and the method of Owens and Wendt (67). These results are summarized in Table X (7, 67, 72-74, 76, 77), in which PTFPMS is compared with two other fluorocarbon polymers, poly(tetrafluoroethylene) (PTFE) and poly(chlorotrifluoroethylene) (PCTFE). PTFE behaves like PTFPMS, whereas PCTFE behaves like PDMS. 

Attenuated total reflection infrared critical micelle concentration electron spectroscopy for chemical analysis hydrophilic-lipophilic balance poly(chlorotrifluoroethylene) poly(dimethylsiloxane) poly(tetrafluoroethylene) poly(trifluoropropylmethylsiloxane) glass transition temperature critical surface tension of wetting Owens-Wendt solid surface tension surface tension of aqueous solution surface tension of liquid... 

In order to determine the contact angles (0) (Eq. 2) of aqueous surfactant solutions (c > cmc) on an apolar perfluorinated surface (FEP , Du Pont, solid surface tension 18.9 mN/m) the surface tension (y, ) and the wetting tension (a) have been measured [7],... 

The properties of the liquid precursors (Table 2) were investigated by wetting experiments on a perfluoroalkyl methacrylate (FC 722 , 3M) covered glass plate (solid surface tension y 12.5 mN/m)[ll]. 

Thus the spreading coefficient is equal to b-7, the difference between wetting an surface tension of the liquid. Since the spreading of a liquid presumes a contact angle 0 = 0 between the liquid and the solid phase, a positive value of S is needed. Positive S-values are obtained only if the sinface tension of the liquid is less than of the solid. The surface tension of liquids can be determined very easily, while for solid surfaces it is impossible to determine directly. If we assume that the minimal surface tension of an aqueous solution of a conventional surfactant is in the range of 25 - 30 mN/m, then paraffin can be wetted only if its surface tensions is higher. 

Ensure operation in the correct flow regime. The effectiveness of the solid catalyst and of the gas-liquid mass transfer decrease if solid catalyst is not wet. For good wetting of the solid keep the surface tension of the solid > surface tension of the liquid. Prevent foaming. The efficiency depends on the skill in initially distributing the gas and the liquid. Use liquid distribution plate similar to design used for packed towers. The liquid distribution plate should have at least 50 holes/ m of catalyst bed. 

Pioneering work on the evaluation of solid surface tensions was carried out by Zisman and co-workers. The principle was to measure the Contact angles 0q of a series of liquids of decreasing surface tension y on the polymer surface (see Critical surface tension). As the value of y decreases, so does that of 6q, whereas cos 0q increases. By plotting a graph of cos 0q versus y, extrapolation can be made to cos 0q = 1 (even if a liquid in this neighbourhood is only hypothetical). The value of y for cos 0o = 1 is known as the critical surface tension for wetting of the solid yc and corresponds to the value of the surface tension of a liquid that will just spread spontaneously. It does not, in fact, correspond... 

Surface tension (called cohesion) and the natural tendency of water to wet solid surfaces (called adhesion) result in capillarity, which allows water to climb a tube or wall. If water had a weaker surface tension (and consequently weaker capillary forces), water in the soil would not be able to overcome gravity, and plant life would die. 

The situation as depicted in Fig. 3 is only one of two possible configurations. The second situation is the one of complete wetting, and it is characterized by the presence of a macroscopically thick layer of one of the phases between the other two (see Fig. 5). Whereas in the case of partial wetting the three surface tensions involved obey Young s law, in the case of complete wetting the surface tensions are related through Antonow s rule [22,23], which states that the surface tension of the solid-vapor interface, when it is intruded by a macroscopically thick liquid layer, is given by the sum of the surface tensions of the solid-liquid and liquid-vapor interfaces... 

The measured normalized wetting rates for various test liquids (for cellulose fibers Fig. 23) ean be transformed into the cosine of the contact angle (cos0) and plotted as a function of the liquid surface tension (Fig. 24). The resulting linear relationship cos 0=1 b(yi — yc) was established empirically by Zisman and Fox [120] and found to hold for solid with low surface tensions. The eritical surface tension yc corresponds to the surface tension of the liquid that will just spread over/wet eompletely the soUd. The constant C reflects the eapillary geometry of the porous solid and may change in a non-predictable manner during the penetration proeess of different test liquids. It was concluded from the experiments performed [112] that there is no need to determine the constant C in order to obtain solid-surface tensions, because the position of the maximum in the C yiv cos 6 vs. yiv plot, which is expected to... 

AG = yiv cos 9 + W i — W, if the same liquid as in case (iii) is wetting the bare nonpreequilibrated solid surface. Using the acid-base approach to estimate the solid surface tension we obtain ... 

Once the effective pore radius parameter fp was determined [Eq. (58)] in a first experiment using a liquid with known surface tension yiv and viscosity that wets the solid completely, it will be possible, according to Refs. [116,128, 130], to use the appropriate AG-values from cases (iii) and (iv) to determine the solid surface tension components. 

Solid Surface Tension (Wetting Properties of Solid Surfaces)... 

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