Equilibrium spreading coefficient

The final or equilibrium spreading coefficient is therefore negative thus if ben-... 

The surface pressure can also be calculated from the difference between the values of the semi-initial and equilibrium spreading coefficients... 

Equation (468) is equivalent to Harkins s equation (Equation (460)). However, we must also consider the effect of the mutual saturation of the liquids on the equilibrium spreading coefficient, S /2. After the initial contact of oil and water molecules [or liquids (1) and (2)], they will become mutually saturated within each other after a while, so that yw will change to y o) and y0 to y)(W). At equilibrium, Equations (460) and (461) turn into... 

An alternative to the relationship in Equation (17.10) is the so-called equilibrium spreading coefficient... 

Surface properties In the interaction of polymers with other materials (liquid or solid), surface properties are critical, (a) The interaction of polymer surfaces with liquids in this case, the important phenomena are the wetting and spreading and these affect the adhesion of polymer surfaces applied in the Uqnid state. When a liquid is brought into contact with a polymeric sohd, the extent of wetting is described by the contact angle 0 which a hquid droplet makes with the surface at the three-phase contact hne. When a hquid wets a polymeric sohd to the extent that the contact angle becomes zero, the equilibrium spreading coefficient S is defined as in Eq. 1.16 ... 

When a droplet is placed on a solid surface, either it does not move and has a definite contact angle between the liquid and the solid phase, or it spreads across the surface to form a wetting film [39]. This criterion is expressed by defining a parameter termed the equilibrium spreading coefficient, Sus, where... 

In this context we may define a spreading pressure as the reduction in equilibrium surface tension, Ao w. of the air-water surface caused by the addition of oil to the aqueous surface. In the case of the classic spreading coefficients, it is given by the difference between the semi-initial and the equilibrium spreading coefficients as shown by combining Equations 3.6 and 3.7 since... 

Denkov et al. [54] have made a detailed stndy of the role of PDMS oil in the mode of action of mixtnres of such oils with hydrophobed silica. The work concerned the effect of such an antifoam on micellar (10 mM) aqueous solutions of AOT. The chosen system was characterized by a positive initial spreading coefficient and a slightly negative equilibrium spreading coefficient for the oil on the snrfactant solntion (see Table 3.3). Both the equilibrium entry coefficient and the bridging coefficient were positive with the latter close to the limit permitted by condition 4.31. The system... 

Pseudo-partial wetting is also often found with both PDMS and short-chain alkane oils. However, as we have described in Section 3.6.1, in the case of such spreading on aqueous micellar surfactant solutions, equilibrium spreading coefficients are usually close to zero. This indicates that the films in equilibrium with oil lenses are relatively thick and are close to duplex in character. In turn, this means... 

With this weight of authority we may confidently dismiss all reports of positive equilibrium spreading coefficients as due to experimental error incomplete equilibration or imprecise measurement. 

These criteria may also be expressed by defining a parameter termed the equilibrium spreading coefficient, S, where ... 

When a liquid wets a solid to the extent that the contact angle becomes zero, the liquid is said to spread such that for each unit area of solid/vapour interface which disappears equivalent areas of solid/liquid and liquid/vapour interfaces are formed. The equilibrium spreading coefficient S is defined as... 

The equilibrium spreading coefficient can be either negative (partial wetting) or zero (perfect wetting). There are conditions (e.g., when a liquid first contacts a solid, or when a liquid phase is produced via melting) when the solid surface is not in equilibrium with the vapor of the liquid. Setting (Tsv = o so + o sv in Eq. (5), it follows that ... 

When an oil droplet within a liquid film arrives at one of the surfaces of the film, it may or may not enter the surface (see Fig. 10) [14,15,37]. It is possible that a metastable thin aqueous film is formed between the oil drop and air. Assuming that this film, if present, can be ruptured in some way, then in an equilibrated system it is thermodynamically feasible for the drop to enter the surface if the sum of the equilibrium oil/water and air/water interfacial tensions (yow and yaw respectively) exceeds that of the oil/air interface (yoa). For this reason it is usual to define an equilibrium spreading coefficient, 5w,oa for water spreading on the oiFair interface as... 

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