(114d) Characterization of Interparticle Forces in Aqueous and Nonaqueous Dispersions Using Multisample Analytical Centrifugation

The behaviour of dispersions in liquid media, i.e. dispersion stability, flow, separation and packing behaviour, is determined by the nature and degree of interparticle forces. This is of fundamental importance for their application in diverse fields such as nanomaterials, coating, paper making, ceramics, sludge dewatering, to name just a few. The present work reports on the use of multisample analytical centrifugation for investigation of the packing and compression behaviour to characterize the colloidal stability and microstructure in aqueous and nonaqueous dispersed systems. Packing density, obtained after compression, is related to the total interparticle potential energy. By using different additives interaction between particles can be shifted from nearly hard sphere behaviour to strong attraction which results in flocculated systems. Additional information could be obtained about the strength and elasticity of particle networks by analysing the relative change in sediment volume after increasing/decreasing the excess pressure in multiple cycles. The multisample technique applied implies the potential for more systematic studies for targeted colloidal stability. The new multisample approach uses the STEP-technology. Space and time resolved extinction profiles quantify the alteration of particle concentration and packing behaviour during centrifugation without the need for sample dilution. The latter is a necessary prerequisite for ensuring that the liquid dispersions maintain their original properties. The paper further covers the influence of the nature of interparticle forces on segregation and deliquoring of common polydisperse fine particle slurries in the centrifugal field.