Surface tension polar component

Surface tension of polymers can be divided into two components polar (y ) and dispersion (7 ), to account for the type of attraction forces at the interfaces. Chemical constitution of the surface determines the relative contribution of each component to the surface tension. Polar component is comprised of various polar molecular interactions, including hydrogen bonding, dipole energy, and induction energy, whereas the dispersion component arises from London dispersion attractions. The attractive forces (van der Waals and London dispersion) are additive, which results in the surface tension components being additive 7 = 7 + 7 . 

According to the ion interaction model, a high surface tension is generated between the non polar stationary phase and the polar mobile phase. From this, the stationary phase obtains a high affinity towards those components of the mobile phase which are able to reduce the high surface tension. Such components include, for example, polar organic solvents, surfactants with their respective counter ions, and quaternary ammonium bases. Moreover, the model con-... 

Good, van Oss, and Caudhury [208-210] generalized this approach to include three different surface tension components from Lifshitz-van der Waals (dispersion) and electron-donor/electron-acceptor polar interactions. They have tested this model on several materials to find these surface tension components [29, 138, 211, 212]. These approaches have recently been disputed on thermodynamic grounds [213] and based on experimental measurements [214, 215]. 

Liquid-Phase Components. It is usual to classify organic Hquids by the nature of the polar or hydrophilic functional group, ie, alcohol, acid, ester, phosphate, etc. Because lowering of surface tension is a key defoamer property and since this effect is a function of the nonpolar portion of the Hquid-phase component, it is preferable to classify by the hydrophobic, nonpolar portion. This approach identifies four Hquid phase component classes hydrocarbons, polyethers, siHcones, and duorocarbons. 

Geometric mean approximation Dispersive and polar components of solid surface energy are found by solving yiv(l +COS0) = 2(y,Xf + 2(y Yl S An extension of GGF equation ysa predicted is significantly higher than the critical surface tension. [84]... 

Because lowering the surface tension is the most important physical property of a defoamer, it is reasonable to classify the defoamer by the hydrophobic operation of the molecule. In contrast, the classification of organic molecules by functional groups are often polar and hydrophilic (i.e., alcohol, acid, and salt are common in basic organic chemistry). Four classes of defoamers are known as liquid phase components ... 

The presence of the polar hydrogel on the surface of PET films led, as seen from Table V, to a decrease in their contact angle with water and to a corresponding rise of the critical surface tension through the polar component... 

Although it was assumed that Eq. 10 is also valid 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 a polar component of the surface tension, but the latter includes all polar interactions [34]. Thus interfacial interaction can be calculated as follows ... 

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). 

Table 2. Surface Tension of Selected Polymers and Fillers Dispersion (f ) and Polar (yP) Components ...

Equation 24 is derived from the Young (Eq. 21), the Dupre (Eq. 8) and the Eowkes (Eq. 10) equations by assuming complete wetting (cos 0 =0). Measurements with polar solvents give the polar component of the surface tension, but acid/base constants and the corresponding work of adhesion can also be calculated from them ... 

Here the superscript prime symbol refers to the dispersed phase, // is the viscosity, vr and ve the radial and tangential velocity components, 0 and r are the polar coordinates, and a is the surface tension. In the case under consideration,... 

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],... 

The extent to which surface tension can be controlled by fluoroalkyl-containing coupling agent type treatments is summarized in Table 1. Its purpose is to simply illustrate the range of control possible detailed comparisons are unwarranted because of differences in sample preparation and choice of substrate, data acquisition and treatment. Some of the critical surface tensions (crc) are obtained with -alkanes, some with other liquids. Some of the dispersion force components (of) and polar components (of) of solid surface tension are derived by use of different equations. The reader is referred to the key references in Table 1 for full details. 

The dispersive and polar components of the surface tensions of the liquids were estimated to be 7 = 21.8 mN/m and 7 = 51.0 mN/m for water and 7 = 49.5 mN/m and 7 = 1.3 mN/m for methylene iodide. This estimation was done by measuring contact angles with various hydrocarbons and assuming that there are only nonpolar interactions. What are the surface energies, 7s, of the polymers ... 

Table 1 Surface tensions y, dispersive components yD and polar components yp of water and diiodomethane. Data taken from Strom [22]...

Note All data are from references 88 and 89 except where indicated, is the nonpolar component of surface tension, is the polar component of surface tension, and o sv is the Owens-Wendt solid surface tension. All values are in units of millinewtons per meter. 

In order to study molecular associations we may consider binary liquid mixtures whose constituents do not react chemically with one another and investigate the connexion between the polarity of the molecules of the components and other physico-chemical properties such as vapour pressure, viscosity, surface tension, c. 

On the basis of Equation 4, the values of ya and y/ for a solid polymer surface can be calculated from the contact angles on it of two liquids, the surface tensions of which have been defined in terms of the respective contribution of dispersion and polar force components (5). In this case. Equation 4 is rearranged to two simultaneous equations, and solved for y/ and y/. 

Turning now to the solid/water/oil measurements, we compare the predicted Ooic values according to Equations 14 and 15 with experimental values in Tables IV-VII for the substrates investigated. In the case of Teflon, where it is possible to test Equation 11, values are given for heptane and n-hexanol. The dispersion and polar components of the surface tension of water-n-hexanol, i.e. water saturated with n-hexanol, and hexanol-water were obtained by measuring the contact angle of liquid drops on paraflSn wax (ys = 25.5 dynes/cm), which served as a... 

Emulsifying properties. One of the major functions of commercial lecithins is to emulsify fats. In an oihwater system, the phosphohpid components concentrate at the oUrwater interface. The polar, hydrophilic parts of the molecules are directed toward the aqueous phase, and the nonpolar, hydrophobic (or lipophilic) parts are directed toward the oil phase. The concentration of phospholipids at the oihwater interface lowers the surface tension and makes it possible for emulsions to form. Once the emulsion is formed, the phosphohpid molecules at the surface of the oil or water droplets act as barriers that prevent the droplets from coalescing, thus stabilizing the emulsion (159). 

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