Probable mechanism of origin of disjoining pressure between rubbing solids at mixed friction
It is believed that hydrodynamic microwedges appear in gaps between asperities of the contacting surfaces during transition from boundary friction to mixed one. The insufficiency of these views for explaining decrease in the friction force at low sliding velocities is substantiated. It is shown that in transition to the mixed friction regime the nature of the equilibrating pressure may have osmotic character. A molecular-kinetic model of the occurrence of the disjoining pressure at mixed friction due to the desorption of surfactant molecules from the friction surfaces is proposed. Desorption is induced by the velocity gradient in the lubricating film that results from the sliding of the solids. The simplest estimates of the disjoining osmotic pressure for various surfactants are made