Journal of Adhesion Science and Technology, Vol.17, No.14, 1945-1956, 2003
Adhesion between silica particles in an alcohol medium
The destruction times of the sediment column structures of hydrophobic and hydrophilic silica particles were measured using a simple device. Experiments were carried out for different fractions of both silica particles in alcohols ranging from ethanol to decanol. On the basis of linear relationships between the reciprocal of the destruction times of the silica sediment column structures and average diameters of the silica fractions, the density of alcohols and the work of cohesion of alcohols, and the critical values of these parameters were determined. For the silica particle/alcohol/silica particle system having a critical value of the average diameter of the particle (or the critical density of alcohol, or the critical work of cohesion of alcohol), the detachment force of one silica particle from another was found to be equal to the attachment force between them. The values of the detachment force were found to decrease with increasing length of the hydrocarbon chain of the alcohols. Using these force values and the critical work of cohesion of alcohol, the radii of the contact planes between two silica particles and then the attachment forces were calculated. The attachment force values increased with increasing length of the hydrocarbon chain of the alcohols. It has also been found that the critical parameters (diameter of silica particles, density and work of cohesion of alcohols) depend on the surface properties of the solid. Hydrophilization of the silica surface caused an increase of the average critical diameter and the critical work of cohesion and a decrease of the critical density and, as a consequence, an increase of the attachment force. The increase of the destruction time with increasing length of the hydrocarbon chain of alcohols was caused, on one hand, by the decrease of the detachment forces and the perimeter of the contact planes, and, on the other, by the increase of the attachment force.
Keywords:hydrophobic silica particles;hydrophilic silica particles;alcohols;attachment forces;detachment forces