Tension adhesion

There is no direct way by which ygy or y can be measured. The difference between ysv and y L can be obtained from contact angle measurements. This difference is referred to as the Wetting Tension or Adhesion Tension , 

Combining Eqs. (11.14) to (11.16) with Young s equation, Gibbs arrived at the following equation for the adhesion tension, 

the adhesion tension depends on the measurable quantities lv As 

Consider a liquid drop with surface tension lv a solid surface with surface tension ygy- When the liquid drop adheres to the solid surface it forms a surface 

The work of adhesion [6, 7] is simply the difference between the surface tensions of the liquid/vapour and solid/vapour and that of the solid/liquid, 

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This distinction between 7 s and 7svo seems first to have been made by Bang-ham and Razouk [33] it was also stressed by Harkins and Livingstone [34]. Another quantity, introduced by Bartell and co-workers [35] is the adhesion tension A, which will be defined here as... 

Both here and in Eq. X-19 the subscript SLV serves as a reminder that the work of adhesion and the adhesion tension involve 75 0 rather than 75. 

Using the data of Table X-2, estimate the contact angle for benzene on aluminum oxide and the corresponding adhesion tension. 

Bartell and Flu [19] were able to determine the adhesion tension, that is, ysv -7SL. for the water-silica interface to be 82.8 ergs/cm at 20°C and its temperature change to be -0.173 erg cm K . The heat of immersion of the silica sample in water was 15.9 cal/g. Calculate the surface area of the sample in square centimeters per gram. 

The contact an e or adhesion tension of a binder solution with respecd to a powder can be determined from the slope of the penetration profile. Washburn tests can also be used to investigate the influence of powder preparation on penetration rates. The Bartell cell is related to the Washburn test except that adhesion tension is determined by available gas pressure which opposes penetration. [Bartell Osterhof, Ind. Eng. Chem., 19, 1277 (1927).]... 

Increase adhesion tension. Maximize surface tension. Minimize contact angle. Alter surfactant concentration or type to maximize adhesion tension and minimize Marangoni effects. Precoat powder with wettahle monolayers, e.g., coatings or steam. Control impurity levels in particle formation. Alter crystal hahit in particle formation. Minimize surface roughness in milhng. 

Fig. 18. Adhesive contact of elastic spheres. pH(r) and pa(r) are the Hertz pressure and adhesive tension distributions, (a) JKR model uses a Griffith crack with a stress singularity at the edge of contact (r = a) (b) Maugis model uses a Dugdale crack with a constant tension aa in a < r < c [1111.

TABLE II. ANAEROBIC CRUDE OIL ADHESION TENSION MEASUREMENTS AND CONTACT ANGLES USING IFT = 36.4 DYNE/CM... 

Interface Measured Adhesion Tension Calculated Contact Angle... 

Additive solutions, in porous media, 279-282 Adherent barrier, physicochemical properties, 636 Adhesion tension... 

Increase Adhesion Tension Maximize Surface Tension Minimize Contact Angle Determine the critical surfactant concentration to maximize adhesion tension. Control impurity levels in particle formation... 

Adhesion Tensions and Tar Sand Extraction with Tween Surfactants. Mea-surement of the adhesion tension (t) allows the determination of the wettability of a given solid by a given liquid or surfactant solution. Measurements of adhesion tension between both bitumen or clay surfaces and various surfactant solutions is thus highly relevant to a study of the effects of surfactants in the separation of bitumen from Athabasca tar sand. 

Fig. 10 relates the composite extraction index (see above) obtained in the low-shear aqueous test system for these Tween surfactants, and adhesion tensions measured against various solids. Adhesion tensions against platinum and bitumen saturated pyrophyllite are irregularly related to tar sand extraction, while the adhesion tension against a fresh pyrophyllite surface is linearly (inversely) related to tar sand extraction. This is the first linear correlation between a measurable property of a surfactant solution and tar sand extraction which we have been able to obtain, and there appears to be no such finding in the literature. Fig. 11 gives the relations between extraction of bitumen with the paddle mill, solvent-aqueous-surfactant extraction and adhesion tensions measured against platinum, bitumen saturated pyrophyllite and hydrated (48 hours in water) pyrophyllite. 

Figure 8, Adhesion tension vs, HLB, Tween surfactants. (9) Fresh surface of pyrophyllite (O) hydrated pyrophyHite (O) bitumen-saturated pyrophyl-...

Figure 9. Adhesion tension and HLB vs. spreading tension, Tween surfactants. Symbols as in Figure 8 ([J) mica f ) spreading tension against a 20% (w/v) solution of bitumen in kerosene.

Figure 10, Aqueous-surfactant extraction of tar sand (composite extraction index) vs, adhesion tension against various solids for Tween surfactants (0.02% w/v). Symbols as in Figure 8.

A linear correlation is obtained between bitumen extraction with the paddle mill and the adhesion tension against water saturated pyrophyllite. That the degree of water saturation of the pyrophyllite is important in explaining the difference between the 2 extraction processes indicates that it will be necessary to study each process in terms of the relevant adhesion tensions. These results demonstrate that adhesion tension is the most important parameter found to date in determining the degree of separation in the presence of surfactants. Measurements of adhesion tension between surfactant solutions and minerals similar to those found in tar sand may be of considerable value in studies of surfactant utility in both aqueous-surfactant, solvent-aqueous-surfactant and in situ extraction processes. In addition, if appropriate model situations can be developed, measurements of adhesion tension may be useful in upgrading bitumen-water-clay emulsions obtained by a variety of in situ and heavy oil recovery processes. 

There is no known method for determining directly the surface tension of solids against gases. However, we can determine the difference surface tension parallel to the solid surface. Thus, for equilibrium... 

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