Good-Girifalco

The Good-Girifalco theory [77-82] was originally formulated to make an attempt to correlate the solid-liquid interfacial tension to the solid surface energy and the liquid surface tension through an interaction parameter, basic formulation of the theory is ... 

Fluorocarbon and hydrocarbon modified PDMS surfaces are compared in Table 2. The contact angle data are obtained by the Good-Girifalco-Fowkes equation. It is striking that the hydrocarbon contact angle liquid gives better agreement with the JKR result for the hydrocarbon surface whereas the fluorocarbon liquid data better fit the fluorocarbon surface... 

Table 3. Surface tension of RSi03/2 treatments (derived by Good-Girifalco-Fowkes approach except where noted)... 

Good-Girifalco-Fowkes (GGF) equation Using Xsi = Xsv + yiv - 2(ysvyiv) in Young s equation leads to 1+COS0 Xggf obtained from a plot COS0 versus 4> is solid-liquid interaction parameter 0 = 1 if the interactions are purely dispersive. Based on Berthelot relation for atuactive constants valid only when the solid-liquid interactions are dominantly dispersive. [77-82]... 

The Good-Girifalco approach has been extended to the use of contact angles in the computation of surface tension values for solid-liquid interfaces. Considering a system where the fluid 2 is either vapor or air (in which case it can be ignored), and combining with Young s equation, one obtains the expression... 

While determined value, depending to some extent on the nature of the liquids us for its determination, attempts have been made to identify it with such theoretical terms as or o-s. According to the Good-Girifalco equation [Eq. (17.27)], for jts.i = 0 and cos 0=1... 

From a practical applications point of view, both the critical surface tension approach and the use of contact angles with the Good-Girifalco-Fowkes equation represent handy tools for the characterization of the wettability, and therefore something of the chemical nature, of solid surfaces. The choice of technique is basically one of preference and convenience. 

Many different measures may be used to specify this fundamental adhesion. It may be expressed in terms of forces or in terms of energies. Again, depending on the context, these may be forces or energies of attachment or else of detachment. Sometimes values of fundamental adhesion can be calculated from a theoretical model (see Electrostatic theory of adhesion, Good-Girifalco interaction parameter) occasionally, they may be deduced from experimental measurement (see Adhesion-fundamental and practical) for many practical adhesive bonds, they are not available by either route. 

Further insight comes from consideration of the Good-Girifalco interaction parameter theory, which gives the following equation. 

By incorporating the definition of and Wq (see Contact angles and interfacial tension), Eqn. 1 can be rearranged to give the Good-Girifalco equation for interfacial tension Yi2 in terms of the Surface energy values yi and yi of the two phases... 

The second problem involves interpretation of the interfacial tension ysL (there is no difficulty concerning = y since the liquid must coexist with its vapour). The interfacial tension must be lower than the snm of the two individual surface tensions (otherwise the interface would not form) by an amount related to them (it is a consequence of the same forces that give rise to the individual surface tension). Good and Girifalco expressed this (see Good-Girifalco interaction parameter) as... 

One justification for the geometric mean term in Eqn. 4 comes from the Good-Girifalco equation... 

If dispersion forces are the dominant bond type in both phase 1 and 2 and the molecules are similar in properties, f will be close to unity. (This is discussed in the Good-Girifalco... 

The theory of the Good-Girifalco interaction parameter can be developed to give some support for this relationship. This was not accepted by Fowkes, who argued that the principal non-dispersion interactions are Acid-base interactions, for which a geometric mean relationship does not apply. 

The concept of surface energy components provides one route to interfacial tensions and solid surface energies and others include the Good-Girifalco interaction parameter and Acid-base interactions. 

Good-Girifalco interaction parameter D E PACKHAM Definition of (p evaluation for dispersion force interface interfacial tension solid surface energies... 

The need to minimize unfavorable interfadal interactions by minimizing the interfacial tension Y12 can also be inferred from the following simplified Good-Girifalco equations ... 

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