Droplets contact angle

FIG. 22-38 Tbe variation of adsorption density, oil-droplet contact angle, and oil-extraction recovery of bematite as a function of pH. To convert gram-moles per square centimeter to pound-moles per square foot, multiply hy 2.048. [From Raghavan and Fuerstenau, Am. Inst. Cbem. Eng. Symp. Ser., 71(150), 59... 

Effects based on physicochemical behaviours Effects based on the structure Shape of the droplet/contact angle Effect of impurities... 

The surface characteristics of reworked substrates and several rework processes are described later in several tables and the discussion. The substrate condition following the rework process is characterized by the results of three tests ESCA or XPS [19] surface chemical composition spectra, actual lithographic resist pattern lift testing [2, 6], and water droplet contact angle measurement, 0HjO [3]. 

I Figure 3. Effect of NaCl concentration on droplet contact angle. Series C... 

Figure 4. Relative increase in interfacial tension as a function of droplet contact angle for increasing NaCl concentrations. Series C films, Cl counterion...

In the case of agar-agar gel, in which the double-sided model represents the hydrophilic moiety, the number of the hydrophilic moieties at the air/gel interface and at the water/gel interface is nearly the same. Consequently, the sessile droplet contact angle of water is low and nearly identical to the sessile bubble contact angle of water. 

Figure 23.6 The effects of the orientation of hydrophilic moieties on the sessile droplet contact angle and sessile bubble contact angle.

Figure 23.8 Advancing and receding sessile droplet contact angle of water on a dry ethylene/vinyl alcohol film.

Figure 23.9 Change of sessile droplet contact angle with water immersion time at 40°C.

The more dramatic demonstration of the creation of interaction force between the surface and a sessile droplet of water can be seen in the measurement of the sessile droplet rolling-off angle, of which principle is depicted in Figure 23.16. If the sessile droplet contact angle is high and no surface configuration change occurs, such... 

Figure 25.2 Sessile droplet contact angle of water on CF4 plasma treated PET films subsequently treated differently (1) samples kept in air (no water immersion), (2) samples immersed in water for 120 min, (3) water immersed samples heat treated at 100°C for 10 min, (4) water immersed samples heat treated at 180°C for 10 min.

The decay of hydrophobicity manifested by the sessile droplet contact angles of water as well as of XPS FIs peak intensity is observed in nylon 6 and PET films treated similarly. There is a direct linear correlation between the contact angles of water and the intensity of XPS F Is peaks for each substrate polymer as shown in Figure 25.4. This correlation confirms that the increase and the decrease of the contact angle of water on the surface of plasma-treated films are due mainly to the change in the surface concentration of fluorine-containing moieties, which enable us to deal with the decay and the recovery phenomena by either measurement. 

Figure 25.4 Correlation between sessile droplet contact angle of water and XPS F Is intensity of CF4 plasma treated Nylon 6 and PET films.

TIME DEPENDENCE OF SESSILE DROPLET CONTACT ANGLE... 

Figure 26.1 depicts the change of water droplet volume with time when the sessile droplet contact angle was measured by placing different size droplets on the... 

ADVANCING AND RECEDING SESSILE DROPLET CONTACT ANGLES... 

The sessile droplet contact angle measurement is a simple and accurate method to obtain information pertinent to the surface energy of a sample. The Wilhelmy balance method, on the other hand, is a very useful method to investigate the surface dynamic aspect of a sample, which will be described in the following sections. The instability of some of plasma-treated polymer surface observed by the Wilhelmy balance method is also described in Chapter 30. 

In sessile droplet contact angle measurement, the advancing contact angle could be used to describe the surface characteristics, but the receding contact angle per se is a meaningless number unless its change with respect to the contact time can be utilized to analyze the surface dynamic nature of the surface. 

Figure 27.1 Correlation between the sessile droplet contact angle and contact angle of air bubble on the surface immersed in water (a) hydrophobic surface, (b) hydrophilic surface.

Figure 30.9. LPCAT treatment under stronger plasma conditions for a longer time yields the more wettable surface. However, the sessile droplet contact angle of a paint on Parylene C surface (resident time 0) is low and minimal change occurred with LTCAT treatment. Thus, the adhesion problem is not due to the wetting difficulty.

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