ADSORPTION, STABILITY AND RHEOLOGICAL PROPERTIES IN ORGANIC LIQUID-PAIRS .2.

The rheological properties and optical densities of aerosil dispersions were investigated in methanol-benzene liquid mixtures and the interactions between the dispersed particles were characterized. Parallel with the rheological measurements the adsorption excess isotherm was measured to determine the composition of the adsorption layer on the surface of particles dispersed in liquid mixtures. A well-defined correlation was found between the rheological parameters and the composition of the adsorption layer in the whole concentration range. The aerosil dispersion has an aggregated structure in pure benzene which is destroyed step by step due to the adsorption of methanol reaching the azeotropic composition (x1a, phi-1a) and Newtonian behaviour was experienced in the range x1 = 0,4-0,6. An additional increase in the methanol concentration of the adsorption layer resulted a new structure formation process and the dispersions showed again non-Newtonian properties. The results of optical measurements and also the rheological data supported that the interactions between particles disappeared around the adsorption azeotropic composition (phi-a = phi-1s = const.) where the excess isotherm had a linear part. The adsorption displacement free energy function had extremity in a given concentration range where the dispersions were obviously stable.