Dispersion surface energy

There are numerous techniques which provide information related to the surface energy of solids. A large array of high-vacuum, destructive and non-destructive techniques is available, and most of them yield information on the atomic and chemical composition of the surface and layers just beneath it. These are reviewed elsewhere [83,84] and are beyond the scope of the present chapter. From the standpoint of their effect on wettability and adhesion, the property of greatest importance appears to be the Lifshitz-van der Waals ( dispersion) surface energy, ys. This may be measured by the simple but elegant technique of... 

The organic molecules or "probes used to investigate the dispersive surface energies of the fiber surfaces were a series of n-alkanes. The probes used to study the non dispersive forces were chosen based on their acidic or basic character as determined by Gutmann (8). Gutmann has practically defined basicity as the donor number, DN, or electron-donor capability in the Lewis sense. The donor scale is based on the value of the molar enthalpy for the reaction of the electron donor with a reference acceptor, SbCl. ... 

Topographical morphology and adhesion forces dispersive surface energy, nanoindentation Surface chemistry elucidation of atomic and chemical bonding composition in solid dosage forms... 

Fig. 1. Dependence of the dispersive surface energy yLW on the surface coverage of different molecular layers covalently grafted to amorphous carbon surfaces.

Dispersive surface energies and specific free energies are shown in Table 2. 

Due to the high number of tested probe molecule it was possible to apply both, the van Oss concept using monopolar probe molecules and the Gutman approach using bipolar probes, ys and ys numbers as well as Ka and Kb are summarised in Table 3 together with the dispersive surface energies. 

The dispersive surface energies and the specific free energies as well as the acid-base numbers are significantly higher for the catalyst in comparison to the pure support. 

If the results are compared to those obtained from DVS experiments, it becomes obvious that the relative trends for the dispersive surface energy as well as the ys numbers are similar. 

Figure 7.1 Time-dependent increase of non-dispersive surface energy for polyurethane immersed in water. Polymer cure code C2 (Table 7.1). Immersion at (a) 38.5 °C,...

Figure 11 Effect of 15 KV, 20 iamp, corona treatments on non-dispersion surface energies of polymers.

The contact angle is measured in a series of liquids with varying polar and dispersion surface energy components. The components of the fiber surface energy can be determined by plotting the left-hand side of Eq. (7) as a function of of... 

The thick-flhn limit of the lubricant dispersion surface energy is yf = 13 mJ/m [22]. The dispersion component of the surface energy of the slider is Yi. For the uncoated slider, yf = 43 mJ / m, and the coated slider values are given in table 4.10. The adhesion stress is listed in table 4.13. Further discussion of adhesion-controlled friction is given in the literature [23]. 

Using this expression for water—hydrocarbons interfacial tension (y h) die dispersive surface energy component of water may be found. As basic components for hydrocarbons should be zero, the dispersive component is the surface tension of the hydrocarbon. Measuring yu, Yw> and YwH die only unknown is y which turns to be... 

Wher y and yi are the dispersive components of the solid surface and the interactive solutes phase, respectively. N is Avogadro s number and a is the area of the adsorbed molecules (solutes). In IGC experiments a series of interactive solutes, such as alkanes, can be injected into the chromatographic column in order to determine the dispersive surface energy, ys. A plot of AGi or (RT In Vg°) versus the number of carbons in the alkane chain can be meaningful, since such a plot is linear and the slope of the straight line will account for the incremental contribution of AGi. The molar enthalpy of adsorption can also be calculated from AGi as follows ... 

Combining equations (16) and (17) yield the dispersive surface energy as follows ... 

Where ycm is the surface energy of a hydrocarbon consisting only of n-alkanes, acH2 is the area of one -CH2- group. Equation (18) usually tests the IGC method for obtaining the dispersive surface energy of polymers. 

The dispersion surface energy, y > 1 difference between the energies of bLxlk and surface vacancy formation for the appropriate number of molecules, n, to make up unit area, a, and is given by... 

Inverse gas chromatography analysis at very high dilution and at finite concentrations of probe injection was carried out on a series of polymers and pigments used in paint formulations. Values of dispersion surface energies, and of acid-base interaction parameters were obtained for the materials, and pair interaction parameters were calculated from the results. The dispersion stability of each pigment/ polymer combination was measured and correlated with the acid-base interaction parameters of the materials, and is shown to justify the availability of fundamental thermodynamic interaction data to optimise performance aspects of protective coatings. 23 refs. 

---