Disjoining Pressure

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Disjoining Pressure


a thermodynamic parameter that characterizes the state of a thin layer, or film, of liquid or gas in the gap between the surfaces of bodies. When the system is in equilibrium, the disjoining pressure is P = P2P1, where P2 is the normal pressure on the film exerted by the bodies, and P1, is the pressure in the volume of liquid or gas from which the film was formed (Figure 1). If the disjoining pressure has a positive value (P > 0), then the film is stable; if it has a negative value (P < 0), then the film spontaneously thins until it ruptures.

Figure 1

Disjoining pressure was first detected by the Soviet scientists B. V. Deriagin and E. V. Obukhov in 1934. It arises when two surface layers mutually overlap and is due to the total effect of forces that are different by nature. Thus, electrostatic forces, the forces of “elastic” resistance of solvated, or adsorbed solvated, films, and the forces of molecular interaction can all act as components of the disjoining pressure. The pressure depends on the thickness of the film, the composition and properties of the interacting phases (bodies), and the temperature. The study of disjoining pressure served as the basis for the Deriagin-Landau-Verwey-Overbeck (DLVO) theory of the stability of hydrophobic colloids and explains many surface phenomena. Overcoming a positive disjoining pressure, which prevents the thinning of the film under external forces, leads to adhesion or fusion as the bodies come into contact. In the case of colloidal systems, this means the coagulation or coalescence of particles of the dispersed phase. The disjoining pressure has a decisive influence on the effectiveness of such important practical processes as the swelling and peptization of clayey minerals, the stabilization of foams, and flotation, impregnation, and gluing.


Deriagin, B. V. “K voprosu ob opredelenii poniatiia i velichiny rasklinivaiushchego davleniia i ego roli v statike i kinetike tonkikh sloev zhidkoslei.” Kolloidnyi zhurnal, 1955, vol. 17, issue 3.


The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
This is also linked to rise of capillary pressure, disjoining pressure and surface energy which creates internal compressive stresses in the solid skeleton (Meschke, Pichler, & Rots, 2018).
When the thickness of the wetting film [delta] ~ O (0.1m) [58], mutual interaction of meniscus and solid surface separated by the molecularly thin wetting film gives rise to an additional contribution to pressure inside the film referred to as disjoining pressure [57, 59] which has a crucial effect on the stability of molecularly thin wetting films.
There are four prominent physical models proposed to account for the mechanism of drying shrinkage: capillary tension [5-7], loss of interlayer water [8], changes in surface energy [5], and disjoining pressure [9], of which capillary tension and disjoining pressure are widely accepted.
Dislocation loop dynamics in freestanding smectic films: The role of the disjoining pressure and of the finite permeability of the meniscus.
The macroscopic manifestation of van der Waals forces is known as disjoining pressure. (2-4)
The impossibility of using rollers instead of the die lips is related to their bending under the disjoining pressure forces, resulting in a nonuniform thickness of the final product.
There are also chapters on topics not usually covered in tribology texts but which become important at the small scale, such as capillary condensation, disjoining pressure, contact electrification, and molecular slippage at interfaces.
The intermolecular forces are characterized by the number [PHI], with [phi].sub.ho] denoting the slope of the disjoining pressure
The major cause of cracking from plastic shrinkage is thought to be development of tensile stress as water evaporates from the surface of the concrete, leaving the capillaries partially filled and creating a disjoining pressure due to surface tension.
The main mechanisms of the shrinkage are (a) capillary tension due to moisture change, solid surface tension, and disjoining pressure, (b) chemical shrinkage, (c) thermal shrinkage, and (d) carbonation shrinkage [3].
"The stability of liquid films is affected by a combination of the adhesion between the fiber surface and the liquid film, Laplace pressure and the disjoining pressure of the film," noted Dr.
A free film has three pressures that can act on it--internal bubble pressure, van der Waals disjoining pressure, and electrostatic disjoining pressure [28-30].