Scaling of the viscoelasticity of weakly attractive particles
Edited by Qichao Hu
November 29th, 2010
Colloidal particle suspensions have a diverse range of rheological properties. By adjusting the interparticle interactions and the particle volume fraction, the rheology can be controlled. This paper presents a model that combines the elasticity of a solid network formed by the particles and the viscosity of the suspending fluid.
The example that they used consisted of carbon black suspended in base stock oil, and the experiments were done both as functions of particle volume fraction and interaction potential. This has applications in the automobile industry where suspensions of carbon black in oil are used as test systems to model the behavior of used motor oils where aggregation of soot leads to undesired viscosity increases.
A double-tailed dispersant, acting as a surfactant, is introduced to control the interparticle interactions. The more polar amine group binds to the surface of the carbon black allowing the two long hydrocarbon tails to stabilize the particles. Increasing dispersant concentration in solution leads to increased surface-adsorbed layer, and reduces the attractive interactions between the particles.
The primary particle size of the carbon black is about 30nm using electron microscopy. However, the carbon black particles tend to cluster and aggregate, and large shear is needed to break up the aggregates, and to measure the volume fraction. Without the dispersant, carbon black particles are strongly attractive to each other.