Contact angle measurements, for

Discuss the paradox in the wettability of a fractal surface (Eq. X-33). A true fractal surface is infinite in extent and a liquid of a finite contact angle will trap air at some length scale. How will this influence the contact angle measured for a fractal surface ... 

Synthesis of siloxane-urethane copolymers from various hydroxyalkyl-terminated PDMS oligomers and aliphatic diisocyanates, such as tetramethylene- and hexame-thylene diisocyanate and HMDI was reported 333,334). Reactions were conducted either in chloroform or 1,4-dioxane and usually low molecular weight, oily products were obtained. No data were available on the molecular weights or the thermal and mechanical properties of the copolymers obtained. These products were later cross-linked by a peroxide. Resulting materials were characterized by IR spectroscopy and water contact angle measurements for possible use as contact lenses. 

Contact angle measurements for a water droplet on an asphaltene modified borosilicate surface confirmed that low concentrations of TFSA molecules change the wettability of the surface from fractionally-wet to water-wet. Table II shows the results of the contact angle measurements all reported results are the average of 10 separate measurements, none of which varied from the mean by more than 5° As the concentration of the TFSA... 

The critical surface tension has been evaluated by means of advancing contact angle measurements for water, various hydrocarbon liquids and for plasma polymerized fluorocarbon films " " . The most comprehensive, however, is that of Yasuda... 

Counterion Interactions with Water and Poly cations. The wide range of contact angles measured for the different counterions is no doubt related to the extent of their interaction with water relative to that with the polycations. 

Table 3.5. Minimum and maximum values of contact angle measured for some pure metals on alumina. Results come from data compilations given in references.

No systematic studies have been performed on the anisotropy of wetting. However contact angle measurements for pure Cu on very smooth (Ra = 1-2 nm) surfaces of a-Al203 single crystals revealed contact angle differences of less than 10° (Table 6.2) corresponding to changes in the work of adhesion of less than 150 mJ/m2 (Vikner 1993). These rather weak effects on 0 and Wa do not mean that [Pg.205]

Table 1 Contact angle measurements for wfAFP- or PVP-covered Si02 surface.

Prins and Clint et al. developed a method of contact angle measurement for macroscopic flat foam films formed in a glass frame in contact with a bulk liquid. They measured the jump in the force exerted on the film at the moment when the contact angle is formed. A similar experimental setup was used by Yamanaka for measurement of the velocity of motion of the three-phase contact line. 

The concept for the rupture of a free liquid film or a thin liquid film on a solid substrate is used in some applications, for example in the flotation process. Scheludko et al. (1968) have published first contact angle measurements for liquid films. 

Using UF resins with different degrees of condensation, and hence different viscosities, Scheiki and Dunky [24, 25] showed that higher viscosities of UF resins decreased the penetration into the wood substance. A clear correlation was found between the viscosity of the resins and the initial rate of penetration into the surface, shown as slower decrease of the droplet volume on the surface with time, using the static contact angle measurements, for higher viscosities. Penetration into latewood with narrow lumens was slower than into earlywood with wider lumens. 

The foregoing method can also be employed to determine the adhesion properties of other filled polymer systems. The procedures involved in this analytical method are summar ized as follows (1) Use proper experiments to obtain the contact angle measurements for both the filler and the polymer, (2) Plot the contact angle measurements as cos 9 versus An y and determine the critical surface... 

Table 2 shows typical advancing contact angle measurements for a number of polymers, both before and after plasma treatment. Note that in all cases there is a significant improvement in wetting. Table 3 shows typical values for lap-shear bonding of polymers before and after plasma surface treatment. These data show the great improvement that can be obtained, and the reasons why plasma treatment is used on polymers. 

TABLE 23.3 Contact Angle Measurements for F-POSS Compounds... 

Values of advancing 0a, receding 0r, and static 0q contact angles measured for sessile droplets on a methylated quartz plate in dependence on surfactant concentration [22] are shown in Fig. 19. To determine 0a and 0r, the drop was disposed on a polished surface of a flat cut of a thick-walled quartz capillary over its orifice. For solution concentration Cq< 0.1%, advancing angles are higher than 90° and, therefore, the capillary suction is formally impossible. However, as is shown in Fig. 18, a slow penetration of low concentrated solutions takes place. Similar results were obtained in other experiments with... 

Figure 10.20 Droplet contact angle measurements for water and olive oil droplets plotted as a function of percent HMFS loading. The table lists water and oil droplet roll-off angles (RA) as a function of HMFS loading. Below 50 wt% HMFS loading, all the droplets are pinned [26]. HMFS Hydrophobically modified fumed silica.

Each data point represents the average of measurements at three independent, random locations on the screen surface. Also plotted is the methanol/water contact angle data from Addesso and Lund (1997) obtained using the Whilhelmy plate method. Reasonable agreement exists between the data sets. Methanol mass fraction values in this work were chosen consistent with mass fractions from bubble point measurements. Contact angle measurements for mixtures here are also in qualitative agreement with previously... 

Table 8.1 Surface energy and dynamic contact angle measurements for specified surfaces...

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