Free energy of spreading

By combining Equations (457), (458) and (460), the initial spreading coefficient, S[l2 may be related to the work of adhesion, cohesion and the Gibbs free energy of spreading per unit area ... 

Results with Evacuated Systems. From the observation of the spreading of mercury "under" the gallium the conclusion may be drawn at once that the spreading coefficient (the negative of the free energy of spreading, AF ) is positive ... 

The zero contact angle and strongly negative initial free energy of spreading, on flamed out, evacuated glass, are in accord with expectations based on the behavior of the pure metals on glass. 

Thus, it is deduced that effective adhesion depends critically on the liquid adhesive displacing the third phase and spreading into all the space between the two solid surfaces to be attached to one another. The angle of contact, the hquid surface tension and the disjoining pressure are the appropriate measurable properties that enable quantitative values of the free energy of spreading to be assessed. 

To complete the summary of surface thermodynamic relations, and because we will need certain additional equations later, we include here the equations of spreading thermodynamics. The free energy of spreading (see Figure 2) for liquid i over solid j is... 

Combining Eqs. (3) and (5a), it may be seen that the free energy of spreading is given by... 

Free energy of adhesion Free energy of cohesion Free energy of spreading Glass transition temperature Rate of energy input to filament Volume... 

Table 8 Helmholtz free energy, entropy, and internal energy of spreading and of transition for N-stearoyltyrosine on an aqueous subphase of pH = 6.86 at the transition temperature for each film."... 

Under this connection let mark that the position about an independence of the osmotic pressure of polymeric solutions into concentrated field of the strongly intertwined chains used in the scaling method is successful upon the result (8) in the presented concrete case, but can not be by general principle spreading on the all thermodynamic visualizations of polymeric solutions. For instance, free energy of the macromolecules conformation accordingly to (22) is function not only on the concentration, but also on the length of a chain at any choice of the method for the concentration expression. 

We will define by o-i, ar the two liquid-air and o-ia the liquid-liquid interfacial surface tensions. If cr + o-ia= Ca, it is evident that the system will be in equilibrium, as no decrease in the free energy of the system can take place by spreading or contraction of the drop. On the other hand if... 

For this study, compounds were selected which formed condensed films when spread as a monolayer on water, yet whose solubility in water was sufficiently high to allow measurements of the rate of film desorption from the surface to the bulk solution. For these compounds the free energies of desorption may be obtained from monolayer desorption studies (6). 

If the area occupied by the oil drop shown in Figure 4.16 is increased by dA, the change in the surface free energy of the system will be approximately (y0A + Vow 7wa) cL4. If this quantity is negative, the process of spreading will take place spontaneously. 

In adhesional wetting, a liquid which is not originally in contact with the solid substrate makes contact and adheres to it. In contrast to spreading wetting, the area of liquid-gas interface decreases. The work (free energy) of adhesion is given by the Dupr6 equation (see equation (4.29) in the form... 

The A A are the changes in surface-interface areas. For spreading to occur of the active phase across the support surface, AF must be negative. In the opposite case when AF > 0, islands of the active phase will form on the support which will tend to coalesce into larger particles in order to decrease the free energy of the system. 

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