Dispersive components of surface free

Method based on the quantity, a(yl)1/2 of the London dispersive component, > of surface free energy multiplied by cross sectional area, a, of nonpolar probes, such as n-alkanes [87,125]. 

The work of adhesion increases as the dispersive component of surface free energy increases. Table 5.11 gives the values of the dispersive component available in the literature for different fillers. 

Densification of carbon black by compression increases the dispersive component of surface free energy. This process is initially not proportional to density, but after some threshold value at around 0.7 g/cm the dispersive component has a linear... 

The dispersive component of surface free energy 7 may be calculated from Eq.(ll) with the use of experimentally determined AGcHj [23-47]. 

Surface characteristics of the series of commercially available aluminas with the use of IGC were reported by Papirer et al. [34]. Values of the dispersive component of surface free energy 7 varied from 65 to 100 mJ/m. Authors determined also Kd and Ka values. The variation of the electron donor parameter Kd was almost negligible (2.1-2.7), while Ka parameter increased from 5.6 to 9.9 units. The significant changes for acidity were related to the Si02 content. Acidity parameter, Ka, reached a constant value for a Si02 content of about 1000 ppm. However, AN and DN were taken from Gutmann s proposal... 

Table 7 Dispersive Components of Surface Free Energy of Adsorption and Related Thermodynamic Properties of MSX, SX-I, and SX-II...

Dispersive Component of Surface Free Energy and Related Thermodynamic Parameters... 

A plot of RTln Fn against u(yL ) according to Eq. (30) yields a linear slope of 2A(ys), from which the dispersive component of surface free energy of adsorption, yP, can be determined (60). 

Table 7 contains some values of the polar and dispersive components of surface free energy [57] for some polymers obtained using the geometric and harmonic mean methods. It can be seen that they are in good agreement. 

This represents the dispersion component of surface free energy, taken from reference 66 Calculated using extended Fowkes equation to two components, taken from reference 68 from reference 64... 

Dispersive component of surface free energy of the liquid probe 7 Dispersive component of the surface free energy of the solid Vj Retention volume and C A constant. 

Figure 5.24 shows the effect of oxidation on dispersive and polar components of surface free energy. Carbon fibers were exposed to plasma treatment in the presence of various ratios of CF4 and O2. The untreated sample and the samples exposed to a substantial concentrations of oxygen show increase in the polar component. Fligh concentrations of CF4 gas reduced its dispersive component and converted the surface to a PTFE-like material as confirmed by XPS studies. 

Polar probes have both dispersive and specific components of surface free energy of adsorption. The specific component of surface free energy of adsorption (AGa is determined by subtracting the dispersive contribution from the total free energy of adsorption, and can be obtained from the vertical distance between the alkane reference line [Eq. (30) Figure 21] and the polar probes of interest according to the following equation (60) ... 

In these equations y is the dispersion force component and yP the other polar force components of surface free energy (y = -l- yP). Equation (59.6) was introduced by... 

Table 59.3 is based primarily on the Zisman critical surface tension of wetting and Owens and Wendt approaches because most of the polymer data available is in these forms. The inadequacies of equations such as Eq. (59.7) have been known for a decade, and newer, more refined approaches are becoming established, notably these of van Oss and coworkers [24]. A more limited number of polymers have been examined in this way and the data (at 20 °C) are summarized in Table 59.4. is the component of surface free energy due to the Lifshitz-van der Waals (LW) interactions that includes the London (dispersion, y ), Debye (induction), and Keesom (dipolar) forces. These are the forces that can correctly be treated by a simple geometric mean relationship such as Eq. (59.6). y is the component of surface free energy due to Lewis acid-base (AB) polar interactions. As with y and yP the sum of y and y is the total solid surface free energy, y is obtained from... 

All other polar probes exhibit higher net retention volumes, En. and the difference between their net retention volume and that of the n-alkanes for the same value of the dispersive component of surface energy leads to the value of the free energy of desorption, AGjp, corresponding to the specific acid-base interaction, expressed as ... 

Dispersion force component of surface free energy yf mj - 62 9 (5)... 

London dispersive components of the surface free energy and surface enthalpy... 

The London dispersive component of the surface free energy, y, of a solid may be shown to be a predominant property for the prediction of behavior of nonpolar adsorbents such as polyolefins or of practically nonpolar adsorbents like some carbon materials (natural graphites and carbon fibers). In this section, we propose a simple approach for the determination of the ys using nonpolar probes such as n-alkanes in inverse GC at infinite dilution. We also discuss the evaluation of the London dispersive component of the surface energy (or enthalpy, / ), starting from the variation of the adsorption characteristics, of a series of long-chain n-alkanes molecules, with temperature. 

In the chromatographic process, three methods have been established for determining the London dispersive component of the surface free energy of a solid ... 

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