Contact angle results

Encouraged by the X-ray and contact angle results, we performed some preliminary gas-permeation measurements. Here, a self-supporting film is required and only the longer block copolymers were used. Fluoro-PSB-II and Fluoro-triblock were coated on porous Celgard 2400 membranes the measurements were taken at room temperature at a driving pressure of 5 bars. Since no absolute polymer layer thickness has been determined, only relative values of the permeability are given (Table 10.6). In the case of the separation of C02 from... 

Heyes and Trahar (1984) further compared the floatability of pyrite with the electrochemical and contact angle result reported by Walker and Richardson. Their results are listed in Fig. 3.9. It indicates that the onset of anodic current during a... 

For zero contact angle, cos 0=1 and Wa = 2 yLG = Wc therefore, zero contact angle results when the forces of attraction between liquid and solid are equal to or greater than those between liquid and liquid, and a finite contact angle results when the liquid adheres to the solid less than it coheres to itself. 

Equation (1.46) shows that the contact angle results from the competition of two types of forces cohesion forces responsible for crLv (= Wc/2) and adhesion forces responsible for W . Depending on the strength of S/L and L/L interactions, different contact angles can be obtained (Table 1.1). 

The values obtained for n-hexanol-water were = 24.6 and = 1.9 dynes/cm and for water-hexanol, = 22 and yf = 12.4 dynes/cm. As regards the contact angle results obtained with n-hexanol, values of Oow obtained from Equations 14 and 15 and by experiment show a wide disparity. See Tables IV-VII. For paraffin wax, both equations predict zero contact angle for n-hexanol whereas the experimental values are 45° 6a) and 37°C Or), As discussed earlier, adsorption of alcohols at the solid/liquid interface may affect the wetting behavior of substrates. These effects are not accounted for by the Fowkes or Wu treatment, and hence it is not unexpected that these equations do not correlate with experimental Oow values for hexanol/water. 

The hydrophobicity can be evaluated by measuring the contact angle resulting fi om the equilibrium... 

From Equation (3.73), one can read that for contact angles resulting in flat bubbles ( will be low) the critical voltage If 1 will be reduced. Adding surfactants to the electrolyte is a simple way to change the wettability of the... 

Solid Surface Tension Calculations from Contact Angle Results... 

Figure 4. Water contact angle results for PS/Poly(PEGMA) segregated brushes influence of the solvent treatment.

Since the time that study was made, a large body of experimental data has accumulated which shows that regular and predictable changes in solid-liquid contact angles result from changes in the outermost layer of atoms in the solid surface. A "wettability spectrum" has been published [14],and the utility of the "critical surface tension of wetting" as an index of solid surface energy has been well established. 

Silica films were also prepared on glass microscope slides following the procedure described in the experimental section similar contact angle results to those shown in Fig. 2 were observed. The water droplet shapes on the as prepared silica films with different TFPS/TEOS ratios are shown in Fig. 4. Clearly, the film results follow exactly the same trend as does the silica monolith. SEM images of the surface morphologies of hydrophobic silica films for these TFPS/TEOS ratios... 

Preparation of composites from polyetherimide (PEI) and polyethersulfone showed that the ILSS values are controlled by the work of adhesion as measured by the contact angle. Results by XPS of polymer monolayers gives strong evidence for chemical bond formation in the polymer-carbon interface, but bonds are formed at processing temperatures above 300°C, when —COOH groups are deeomposed, whereas the —C=0 groups are directly involved with bonding epoxies. 

In Figure 7(d) is pictured a bubble in the oil continuum supported by a roughened TFE sphere. It can be suggested for this system, in which the intrinsic contact angle is 60°, that near-zero contact angles result from an inability to drain wetting phase from the sphere surface and composite surface formation is assured. The fluid retained by the surface in this manner illustrates one type of microporosity described by Kieke and Hartmann (19). 

The next step in the analysis is to predict mobilization requirements by coupling the theory presented earlier with the contact angle results of the previous section. The simple cubic geometry will be utilized although the results are broadly applicable to any other geometrical description. Two situations are examined. 

E. Pierce, EJ. Carmona and A. Amirfazh. Understanding of shding and contact angle results in tilted plate experiments. Colloids Surfaces A, 323, 73-82 (2008). 

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