Dispersion component of surface tension

The three EME coupling agents in Table 1 were analyzed using contact angle measurements to determine their polar and dispersion components of surface tension. From the surface tension data, wettability envelopes were constructed and compared with the surface tension properties of the epoxy coating [4], These data predicted that EME 47 would be wet by the epoxy, but not EME 23. This is believed to be the reason for the very low peel strength when EME 23 was employed [4],... 

All non-dispersion components of surface tension lumped together. 

All non-dispersion components of surface tension of i th material lumped together. Melt viscosity. 

Fowkes showed that the carbonyl stretching frequency shifts to lower values as the dispersion component of surface tension increases. The following empirical relationship was proposed ... 

For non-polar liquids, the dispersion component is essentially the total surface tension (see Eqn. 3). For polar liquids, the dispersion component of surface tension can be obtained using Eqn. 4 after measuring both surface tensions and interfacial tension, provided that... 

Latex (emulsion) adhesives. In contact with water, adhesive bonds with latex adhesives may release surfactants, which will have the effect of lowering surface tension and changing the thermodynamic work of adhesion. Some latices based on copolymers of vinyl acetate were dried to give films which were then immersed in small quantities of water. The surface tensions (/w) fell from 72.8 mN m to values in the range 39-53 mN m in the first hour and then remained fairly static [76]. Measurements of interfacial tensions against n-hexadecane showed the dispersion components of surface tension remained essentially constant but polar components were reduced into the range 6-20 mN m ... 

The adsorption of dicarboxyhc acids is more comphcated than that of their monocarboxylic counterparts. They are more polar and the acidic groups situated at both ends of the aliphatic chain offer a variety of possibilities for adsorption. The two groups might be attached to different filler particles, they may be oriented vertically or paraUel to the surface or can also form loops. The changes in the dispersion component of surface tension are plotted against the amount of surfactant used for the treatment for fillers coated with the two dicarboxyhc acids in Fig. 8. The surface tension of the fiber treated with stearic acid is also presented for comparison. Several conclusions can be drawn from the results shown in the figure. A much smaher decrease can be achieved in... 

DF is F gain for the CB content increase in the substratum (PP) from 0 to 42 vol. % calculated from the ratio of polar and dispersion components of surface tension [17]. 

Two test liquids, such as deionized water and formamide of known polar and dispersion components of surface tension were used to evaluate the polar and dispersion components of surface energies of FBI through measurement of their contact angle by the sessile drop method. 

Finally the plot of AH b/AN vs. DN/AN gives and Kj,. Further details of this method are described elsewhere." It can be seen that the procedure is complicated. The conditions of experiments conducted in various laboratories were sufficiently different to affect correlation of data between laboratories. To rectify this situation, a large body of data was obtained for 45 solvents and 19 polymers tested under uniform conditions. Fowkes" showed that the carbonyl stretching frequency shifts to lower values as the dispersion component of surface tension increases. The following empirical relationship was proposed ... 

Wu has proposed to separate the surface energy into non-polar (dispersion) and polar components (Eq. (2.12)). The subscripts d and p designate non-polar (dispersion) and polar components, respectively. The concept of the additive nature of surface energy components has been accepted by a number of researchers such as Fowkes ° and Meyer et al. The polar component of surface tension includes various dipole interactions and hydrogen bonding. The various components have been lumped together to simplify the discussions. The dispersion component includes the nonpolar fraction of surface energy. Fractional polarity is defined by Eq. (2.13) and non-polarity by Eq. (2.14). 

Once the dispersion component of surface energy of a liquid is known, the polar component can be obtained from the surface tension using Eqn. 10. The approach based on Eqns. 9 and 10 can then be used to estimate surface energies of solids, particularly polymers, very much in the same way as Ys values are obtained from Eqn. 8. Here, yi2 is eliminated between Eqn. 10 and the Young equation, giving... 

The Ys values are obtained by the Owens and Wendt approach [10] (Equation 9.3) using water and diiodomethane, where y is the sum of the dispersion force component of surface tension, y, and the polar component, and the subscripts LV and SV refer to the liquid/vapor and solid/vapor interfaces, respectively. 

Although it was assumed that Eq. (13) is valid also when an apolar material enters into interaction with a polar one, in practice polar surfaces interact with each other more often. Several attempts were made to generalize the correlation of Fowkes for such cases and the geometric mean approximation gained the widest acceptance. This considers only the dispersion and polar components of surface tension, but the latter includes all polar interactions [63]. Thus interfacial tension can be calculated as... 

The harmonic mean equation is generally considered to be applicable to low surface tension materials such as organic polymers and liquids. If y and y are known for two liquids, and the contact angles of those liquids on the solid of interest are measured, equation 36 produces two simultaneous equations that can be solved to find the surface tension and polarity of a solid polymer surface. Numerous assumptions have been made in developing the theory of fi actional polarity. For example, it ignores the possibility of induced polarity at the interface between polar and nonpolar materials (82). These assumptions limit the application of equation 36 to systems where at least one and preferably both of the components are relatively nonpolar. The theory breaks down when interfacial interactions lead to molecular rearrangements at the interface between solid and liquid. In addition, it was foimd that pairs of liquids with similar dispersive and polar components of surface tension gave umeasonable results for the substrate surface tension calculated by the harmonic mean method (83). 

Fig. 17. A schematic of the alkane line obtained by inverse gas chromatography (IGC) measurements. The relative retention volume of carrier gas required to elute a series of alkane probe gases is plotted against the molar area of the probe times the. square root of its surface tension. The slope of the plot is yielding the dispersion component of the surface energy of...

The surface tension of two thermoplastics and three fillers are listed in Table 2. Large differences can be observed both in the dispersion, but especially in the polar component. The surface tension of the majority of polymers is in the same range, in fact between that of PP and PMMA. Those listed in Table 2 represent the most important particulate fillers, and also reinforcements used in practice, since clean glass fibers possess similar surface tensions to Si02. Surface treatment lowers the surface tension of fillers significantly (see Sect. 6.1). 

The same logic that we used to obtain the Girifalco-Good-Fowkes equation in Section 6.10 suggests that the dispersion component of the surface tension yd may be better to use than 7 itself when additional interactions besides London forces operate between the molecules. Also, it has been suggested that intermolecular spacing should be explicitly considered within the bulk phases, especially when the interaction at d = d0 is evaluated. The Hamaker approach, after all, treats matter as continuous, and at small separations the graininess of matter can make a difference in the attraction. The latter has been incorporated into one model, which results in the expression... 

The intermolecular attractions between the hydrocarbon chains in the interior of the micelle represent an energetically favourable situation but it is not one which is significantly more favourable than that which results from the alternative hydrocarbon-water attraction in the case of single dissolved surfactant molecules. Comparison of the surface tension of a typical hydrocarbon oil with the dispersion component of the surface tension of water (as discussed on page 67) illustrates this point. 

Fundamental mixing studies on simple two-component systems have provided insight into the effect of mixing parameters on critical emulsion properties such as particle size distribution. For example, Nagata [81] has shown the distribution of sizes of the dispersed liquid phase as a function of agitator speeds. As we might expect, a normal distribution occurs at higher speeds. In a similar study, the effect of surface tension was determined for several liquid dispersed phases from benzene to paraffin oil [82],... 

Figure 7.1. Approximate relationship between the refractive index and the dispersion component of the surface tension.

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