Changes in adhesion force on kaolin under pressures

Different treatment methods have been developed to form technological properties of clay. The methods are thermal, chemical, ultra-violet, mechanical, etc. However, the changes in adhesion force on the surface of the clay particles which have been solidified by pressure have not been thoroughly studied. Therefore, the aim of the paper is to analyze the regularities in changes of adhesion force on the surface of kaolin particles treated by pressure and shear. Kaolin was pressured at Р=800 MPa and sheared by 90°. Adhesion force, roughness, water film thickness on the particle surface and diffractometric parameters were identified on the obtained samples. Experimental research showed that adhesion force illustrates the most significant changes at kaolin treatment under 0 to 125 MPa pressure. A pressure increase from 125 up to 800 MPa on the clay reduces the pressure impact on adhesion force development. These pressure-dependent changes in adhesion force are determined by the presence of defects on the particle surface. Within the pressure range P=0–125 MPa, energy potential on the particle surface results from the defects on the surface (roughness) of the particle and energy determined by the defects of crystallite, while at Р>125 MPa, energy potential appears only due to the energy determined by the defects of crystallite. Thus, pressure changes the defects (energy) both of a crystal lattice and of particle surface. These changes can be seen in the changes of physiochemical properties of clay.