Stability of an Lubricating Adsorbed Film at the Solid/Liquid Interface

Abstract

The coefficient of static friction between a quartz optical flat and silicone rubber plate was measured in an aqueous solution of an anionic surfactant at various concentrations under a varied applied load. The coefficient of friction fell markedly with a surfactant concentration as low as 0.05, which was about the critical micelle concentration (cmc), and rose slightly at higher concentrations. Sudden break in the lubricating action of the surfactant was observed when the vertical load exceeded a particular value that was uniquely determined by the systems chosen. This breakdown pressure increased with increasing surfactant concentration up to a maximum of 10⁴ dyne/cm² at cmc, beyond which it decreased to a value of one half the maximum.