Contact angles equilibrium

Fig. 3. Sessile drop with equilibrium contact angle 6 displacement of edge a distance dx (s solid 1 = liquid v = vapour).

The surface energy of the solid can be obtained from equilibrium contact angle measurements of a series of test liquids on the solid surface, providing the relationship between ysi and the solid yg (in vacuo) and liquid yiv surface energies is known. The exact relationship is given by the Good and Girifalco equation [13,14] ... 

K. R. Shull, T. E. Karis. Dewetting dynamics for large equilibrium contact angles. Langmuir 70 334-339, 1994. 

The equilibrium contact angles for PE and triallyl cyanurate (TAC) grafted PE with water and formamide are presented in Table 7. The grafting of TAC onto PE increases the surface energies of modified PEs [32]. 

Table 7 reveals that the grafting of TAC onto PE decreases the equilibrium contact angles of water and formamide from 92° to 65° and from 75° to 53°, respectively. This decrease is a function of the monomer level and the irradiation dose. At a fixed irradiation dose of 15 Mrad, variation of the TAC level from 0.5 to 3 parts causes a reduction in the contact angles of water by 13° (from 88° to 75°) and of formamide by 11° (from 72° to 61°). This is due to the fact that the concentration of... 

Let us consider a circular puddle of liquid, L, on solid, S, in the presence of liquid vapor, V. The puddle is of radius Rq and small initial thickness Bq. We assume that holes nucleate spontaneously in the puddle and grow with radius r(t) as time t passes because the equilibrium contact angle. Go, is nonzero. The liquid is unstable as a wetting film. Equilibrium thickness of a film, < is given by [27,28]... 

The first term on the right-hand side is due to the hydrostatic pressure (or suction) acting over the base of the rod and the second term is due to surface tension forces around the perimeter. (It should be noted that O is not equal to the equilibrium contact angle 0 but is determined by the meniscus shape.)... 

The value of the equilibrium contact angle (9) at the three-phase line (TPL) produced by a liquid droplet placed on a flat, solid substrate is determined by the balance of interfacial energies at each surface. Thomas Young derived an equation describing this situation in 1804 ... 

The maximum height method measures an equilibrium contact angle and not the advancing angle. The measurement is difficult to perform under vacuum conditions and further difficulties arise because the powder... 

For nonspreading systems, the final spreading coefficient is related to the equilibrium contact angle by the equation... 

ZISMAN, W.A., Relation of the equilibrium contact angle to liquid and solid constitution , A.C.S. Advances in Chemistry Series, 43, 1—51 (1964)... 

Wetting of a solid by a liquid is normally described in terms of the equilibrium contact angle 6 and the appropriate interfacial tensions as shown in Fig. 3.32. 

It is worth noting that if 0a and 0r are equal to the equilibrium contact angle 0, then the first component becomes zero, whereas the second component reduces to the above Equation 21.6. For more information on the difference between 0a, 0r and equilibrium contact angle given by the Young equation the reader may refer to the original works [46, 47]. 

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