Methods plane-parallel discs

Fig. n.l9. Principle of apparatus for measuring the forces of adhesion by the method of plane-parallel discs. 1,2) Discs 3) test liquid 4) compressing load 5) counterweight 6) thermostat. 

In order to study the adhesion of particles in liquid media, particularly in solutions of electrol5d es and surface-active materials, methods, involving crossed filaments and plane-parallel discs, are often used. 

A similar method for estimating the adhesion of mutually perpendicular filaments (glass, quartz, or metal), 0.2-1.2 mm in diameter, was used by Fuks [88]. Fuks also used an apparatus (Fig. 11.19) in which it was possible to determine the forces of interaction between colloidal particles by the method of plane-parallel discs (disc diameters 5-20 mm). 

Hydrodynamic Factor. In order to discover the reason for the dependence of the adhesive forces on contact time, let us consider the hydrodynamic phenomena taking place when the bodies approach or recede from each other. For this purpose it is customary to employ adhesion-simulating methods (see 8), in particular the method of plane-parallel discs. The hydrodynamic factor due [88] to the motion of the liquid in the gap between the contiguous surfaces, determining the change in adhesion with contact time for the interaction of plane-parallel discs, may be represented by the Stefan—Reynolds equation... 

We see from Eq. (TV.39) that the disjoining pressure depends on the extent of the gap separating the bodies in contact, Fuks confirmed this relationship experimentally by the method of plane-parallel discs for solutions of CaCl2, KCl, and NaCl with a concentration of less than 5 mg-equiv/liter. 

In electrolyte solutions (LiCl, NaCl, KCl) adhesion also increases with rising temperature (from 20 to 60°C) this was shown in [46] by the plane-parallel—disc method. A rise in adhesion with increasing temperature was also observed by the crossed-filament... 

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