Rebinder Effect

the drop in mechanical strength and deformation and decomposition of solids through the reversible physicochemical action of a particular medium. The effect was discovered in 1928 by P. A. Rebinder in an investigation of the mechanical properties of the crystals of calcite and rock salt.

The Rebinder effect can occur whenever a solid under stress is brought into contact with an adsorption-active liquid or gaseous medium. It is widespread and is observed in solid metals, in ionic, covalent, and molecular single-crystal and polycrystal-line substances, and in amorphous, porous, and massive partially crystallized glass and polymers.

The basic requirement for the occurrence of the Rebinder effect is a similarity in chemical structure and composition between the two phases in contact—the solid and the medium. The manner and extent to which the effect occurs depend on the intensity of the atomic (molecular) interactions between the phases, the magnitude and type of stress (tensile stress is essential), the rate of deformation, and the temperature. The actual structure of the solid, that is, the presence of, for example, dislocations, fractures, and impurities, plays an important role. The effect characteristically takes the form of a manifold drop in strength, an increase in friability, and a lessening of durability in a solid. Thus, a zinc plate wetted with mercury will not bend under stress but will become friable and disintegrate.

The Rebinder effect can also manifest itself in the plasticizing action of a medium on a solid; this can be seen with water on gypsum and organic surfactants on metals. The thermodynamic Rebinder effect is caused by a decrease in the work required to form a new surface during deformation, a decrease caused by a lowering of the free surface energy of a solid acted upon by the surrounding medium. The molecular nature of the Rebinder effect is seen in the ease with which molecular (atomic, ionic) bonds are ruptured and then rearranged in a solid in the presence of sufficiently mobile adsorption-active molecules (atoms, ions).

The Rebinder effect is used to facilitate the mechanical processing of various materials, especially materials that are difficult to work and materials of extreme hardness. Other important uses include the control of friction and wear through the application of lubricants, the efficient production of finely divided (powdery) materials, and the production of solids and other materials having both particular disperse structures and required combinations of mechanical and other properties through disaggregation and subsequent “repacking” without internal stress. The adsorption-active media, however, can induce appreciable damage, for example, by reducing the strength and durability of the machine parts and materials used in the processes described above. This damage can be avoided, and the materials thereby protected, by eliminating the factors that favor the manifestation of the Rebinder effect.