(339c) Shear-Induced Gelation Phase Diagram for Repulsive Particles

Xie, D., Institute for Chemical and Bioengineering
Wu, H., Institute for Chemical and Bioengineering
Morbidelli, M., Institute of Chemical and Bioengineering, ETH Zurich
Braun, L., BASF SE

Pure shear-induced gelation of repulsive colloidal particles has been investigated in a microchannel without adding any electrolytes. The main attention of this work is to identify the boundary (criticality) for the fluid-like to solid-like transition with respect to particle size, particle volume fraction and shear rate. It is found that at the criticality, the effective particle volume fraction forming the gel network is substantially smaller than the initial particle volume fraction, i.e., only part of the particles participates in the gel network. Such effective particle volume fraction at the criticality increases as either the shear rate or the particle size increases. From the structure factor of the clusters forming the gel network determined by the static light scattering, it is surprising to have found that at the criticality, structure of the clusters is insensitive to the shear rate and primary particle size, with the fractal dimension of about 2.4. Finally, a phase diagram for liquid-like to solid-like transition has been constructed, which unifies the effects of the shear rate, particle volume fraction and particle size on the criticality of the transition.