Surfactant Effects on the Cohesive Strength of Particle Contacts: Measurements by the Cohesive Force Apparatus

Abstract

Highly sensitive devices with magnetoelectric dynamometers and corresponding methods have been elaborated for measuring cohesive strength in the immediate contacts between particles of any nature, in any media. With the use of molecularly smooth particles, the free energy of interaction in coagulation contacts was measured between hydrophilic and hydrophobic surfaces, in various polar and nonpolar liquids, in the presence of various types of surfactants, covering a broad range from tens of millijoules per square meter in lyophobic systems and down to microjoules per square meter in fully lyophilic systems. These data may be used in controlling rheology of various concentrated dispersions. The same technique allows also observing the effects of various media and surfactants on particle bridging (phase contact formation) in the course of mechanical compression, sintering, hydration hardening, and sol–gel transition. These phenomena play principal roles in friction and wear, ceramics formation, mineral binder setting, rock metamorphism, and other technological and natural processes.