Contact angles using

The computer interface system lends itself well to the determination of interfacial tension and contact angles using Equation 3 and the technique described by Pike and Thakkar for Wilhelmy plate type experiments (20). Contact angles for crude oil/brine systems using the dynamic Wilhelmy plate technique have been determined by this technique and all three of the wetting cycles described above have been observed in various crude oil/brine systems (21) (Teeters, D. Wilson, J. F. Andersen, M. A. Thomas, D. C. J. Colloid Interface Sci., 1988, 126, in press). The dynamic Wilhelmy plate device also addresses other aspects of wetting behavior pertinent to petroleum reservoirs. 

TABLE II. ANAEROBIC CRUDE OIL ADHESION TENSION MEASUREMENTS AND CONTACT ANGLES USING IFT = 36.4 DYNE/CM... 

Fig. 3 Diagram of the contact angle used in porosimetry measurements (a) Wetting liquid, 0 < 90° (b) nonwetting liquid, 8 > 90°.

Values of surface solid energy obtained form the advancing contact angles using EQS considering the measured value of water surface tension of 71.8 mN/m... 

The wettability of the PE powders was evaluated in terms of contact angle using the Washburn method [7] with benzyl alcohol and ethylene glycol. Each contact angle value corresponds to the mean value of three measurements. The accuracy of the results is 3°. 

The contact angles using IPTMS are below 60 (Fig 3). The maximum contact angle is obtained at 140 C. Althou the gas concentration of this promoter is hi owing to its low boiling point (94.5 C), the low reactivity resulted in this phenomenon. 

Figure 2. The relationship between treatment times and contact angles using HMDS.

Dependence of relative maximum mobilization pressure drop on contact angle using equation (4) with roughened surfaces. 

FIG. 21 Schematic of experimental apparatus to measure contact angles using a cone surface. 

Fig. 23 schematically shows the principle of the method of using a circular cylinder as the test solid. S, L, and V in the figure indicate solid, liquid, and vapor phases, respectively. The cylinder held horizontally is first immersed and then slowly drawn from the liquid bath. We can see a pair of two-dimensional menisci formed under the cylinder, as shown in Fig. 23a. As the cylinder is raised to a certain critical height, the waists of the two meniscus curves contact each other and the liquid breaks off from the solid surface. The geometry of the two-dimensional meniscus can be determined from the Laplace equation (11) and the contact angle as a boundary condition, as mentioned in Section I. Hence we could calculate the contact angle using the...

FIG. 23 Principle of the method for the measurement of contact angle using circular cylinder based on geometrical instability of two-dimensional meniscus (a) receding contact angle (b) advancing contact angle. 

On the other hand, if one needs to determine contact angles using the capillary-rise method, the constant C can be determined assuming a mean capillary radius and a corresponding number of capillaries... 

Liu et al. 5 treated zinc oxide whiskers using several different coupling agents. Table 3.14 shows the contact angles using different coupling agents with a concentration of 4 wt%. 

Table 3.14 Contact Angles Using Different Coupling Agents with a Mass Fraction of 4 wt%...

Table 14.2 shows a comparison of measured contact angles using ADSA and capillary rise. It can be seen that the capillary rise technique is also able to produce contact angle data with high accuracy, and there is excellent agreement between the two techniques. 

Note that we have obtained the contact angle using the projection of forces on the jc-axis. The question may arise about the projection of forces on the y-axis. In fact, for a liquid surface, the vertical force is balanced by the reaction of the solid. If the solid is replaced by liquid (say, oil), then the surface is distorted to balance the net forces in y-direction (see Figure 5.21). Hence, the resultant forces are zero in both the x- and y-direction. Figure 5.21 shows all the interfaces between adjacent phases to be curved for liquid-liquid-gas interface in contrast to the solid-liquid-gas interface. 

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