Rheological behavior and microstructure of bimodal suspensions of core‐shell structured swollen particles

Abstract

ABSTRACT:The rheological behavior and microstructure of bimodal suspensions of core-shell structured swollen particles have been examined with changing volume ratio of two different sized particles. As the volume fraction of large particles increases, the viscosity, degree of shear-thinning, and the critical shear stress c decreases, while the interparticle distance of the microstructure increases. The suspensions exhibit single mode rheological behavior and have a single diffraction peak in the SAXS profiles. These results suggest that the bimodal suspensions of the core-shell structured swollen particles behave likely to unimodal suspensions of hard spheres with alloy like single mode microstructure composed of hypothetical intermediate size particle. The relationship between c and can be represented as c ϭ 3kT/4 3 , which corresponds to the dynamics of the Brownian hard sphere model with being the particle diameter. These findings indicate that the shear-thinning of the suspensions can be attributed to dynamical competition between the thermal motion and the hydrodynamic motion under shear flow and that the mechanism can be applied to bimodal suspensions of the swollen particles as well as unimodal suspensions of hard spheres.

Particle size effects in colloidal gelatin particle suspensions

“…The increase in viscosity can be correlated to the decrease in particle size with increasing processing shear rate. A suspension with small particles had a higher viscosity compared with one with larger particles (Barnes, 1994;Nakamura and Tachi, 2006;Osman and Atallah, 2006), because part of the continuous phase will be trapped inside the particle clusters. This means that the clusters, increase the effective volume fraction of the dispersed phase (Berli, 2007;Bryant and McClements, 1998).…”

Diffusion, sedimentation, and rheology of concentrated suspensions of core-shell particles

“…There exists a large variety of core-shell particle systems. [1][2][3][4][5][6][7][8][9][10] An example of practical relevance is that of polymer-grafted nanoparticles which play a role in the development of photonic and nanocomposite materials. The polymer coating stabilizes the suspension against flocculation, which otherwise may be induced by the van der Waals attraction in the absence of additional stabilizing mechanisms.…”