Contact angle value

It is clear from our discussion of contact angle hysteresis that there is some degree of variability in reported contact angle values. The data collected in Table X-2, therefore, are intended mainly as a guide to the type of behavior to be expected. The older data comprise mainly results for refractory and relatively polar solids, while newer data are for polymeric surfaces. 

It was pointed out in Section XIII-4A that if the contact angle between a solid particle and two liquid phases is finite, a stable position for the particle is at the liquid-liquid interface. Coalescence is inhibited because it takes work to displace the particle from the interface. In addition, one can account for the type of emulsion that is formed, 0/W or W/O, simply in terms of the contact angle value. As illustrated in Fig. XIV-7, the bulk of the particle will lie in that liquid that most nearly wets it, and by what seems to be a correct application of the early oriented wedge" principle (see Ref. 48), this liquid should then constitute the outer phase. Furthermore, the action of surfactants should be predictable in terms of their effect on the contact angle. This was, indeed, found to be the case in a study by Schulman and Leja [49] on the stabilization of emulsions by barium sulfate. 

Contact angles Contact angle values Contact lenses... 

Table 1. Contact Angle Values for Solids in Contact with Aqueous Media...

The solution concentration also has an influence on the formation of the SAMs. The maps of X-ray photoelectron spectra show that the C(ls) peaks for the samples in 1 mM and 5 mM FTE solutions with 24 h immersing are similar to those in Fig. 20(a), which indicates that there was hardly any SAMs on the DLC surface. The thickness of FTE SAMs and the water contact angle value increased with the immersing time. Hu et al. [26,34] obtained FTE SAMs with a thickness of 1.2 nm and a water contact angle value of about 110° by immersing a sample in a 10 mM FTE solution for 35 hours as shown in Figs. 21 (a) and 21(b). 

For the three sorts of molecules, the film thickness and the water contact angle value of the SAMs grow with increasing chain length. In the immersing time of 1 h, the film thickness obtained is 0.48 nm, 0.8 nm, 1.2 nm, corresponding to the molecules with the number of carbon of 3, 8, and 10, respectively, and the contact angle value is 94°, 107.6°, 110.4°. 

The variations of film thickness and the contact angle value of FDTS SAM are also closely related to the immersing time as shown in Fig. 22. The film thickness of FDTS SAM increases to about 20 A within 2 h, which is close to the molecular chain length of FDTS, and then the thickness in-... 

Fig. 22—Contact angle and film thickness of FDTE SAMs on the DLC surfaces as a function of the immersing time in a 10 mM FDTE solution at the temperature of 60°C (a) contact angle value and film thickness, (b) water contact angle of the FDTS SAM with an immersing time of 12 h.

Table A.4.2 Some Contact Angle Values for Solid-Liquid-Air Interfaces 1> (25° C)...

This yields an equation from which contact angle values, i ), can be determined directly from reflectance readings (see Table 1). 

Fig. 16 Effect of the absorbed dose on the contact angle of PTFE disks. The horizontal line indicates the contact angle value of a commercial PTFE...

The changes in surface properties were analysed both by contact angles and gas permeabilities measurements. The contact angles values for a family of typical liquids are reported on Table 1. The resulting surface tensions, ys, for PE, EVOH and EVO-NO (34,... 

Table 1. Contact angles values (deg.), of typical liquids with polymer surfaces.

Contact angle values -for solids m aqueous media [FLOTATION] (Vol 11)... 

The results obtained proved that very good correlations exist between the value of electrokinetic potential, HPLC results, XPS measurements, contact angle values and changes in the isoelectric point (IEP). 

The increase in the atomic concentration of oxygen (Table 1) suggests an increased amount of hydrophilic groups on the wool surface. This fact can be confirmed by the results of the contact angle measurements (Table 2). Following enzymatic treatment the contact angle is distinctly decreased, from 122.5° for untreated wool to 108° and even 102°, but the wool fabric surface is still hydrophobic (0 > 90°). The contact angle value obtained for wool after an intensive treatment (4% o.w.f. of enzyme) equals the one for wool samples with chitosan deposited. 

Also, Fowkes [90] and Good [91] developed a novel technique for the determination of the work of adhesion, Wa, by employing the surface free energy obtained from the contact angle value in the system of solid-liquid using... 

Figure 2.7. Variations of contact angle with time for ternary silicate glasses containing Si02 and Na20 in a 4 1 mole ratio with additions of Ti02 on Pt substrates (Hocking and Rivers 1982). The R(t) curves are calculated from contact angles values assuming a spherical shape for the drop and taking a...

Table 3.6. Contact angle values in the Au/monocrystalline Al203 system at 1373K.

Table 3.7. Contact angle values in the non-reactive Co-66.6 at.% Si/SiC system at 1623K. in a high vacuum (Gasse 1996).

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