Experimental study on the rheology of anisotropic, flocculated and low volume fraction colloids

• Published in: Korea-Australia rheology journal 2014, 26(1), , pp.105-116
• Main Authors: Ozel, Burcu Genc, Orum, Aslihan, Yildiz, Mehmet, Menceloglu, Yusuf Z.
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Complex Fluids and Microfluidics; Food Science; Materials Science; Mechanical Engineering; Polymer Sciences; Soft and Granular Matter; 공학일반
• ISSN: 1226-119X; 2093-7660
• DOI: 10.1007/s13367-014-0011-7

In this work, we have investigated rheological behavior of colloids with a low particle volume fraction, and anisotropic and flocculated microstructures through measuring their viscosity and electrical resistance under varying shear rates together with utilizing several relevant characterization methods ( i.e. , Dynamic Light Scattering, Transmission Electron Microscopy, Atomic Force Microscopy, and Capacitance and Electrical resistance measurements). The colloids are formed through the suspension of hydrophilic/phobic fumed silica particle with attractive/repulsive interaction in polyethylene glycol and/or ethylene oxide-propylene oxide copolymer. It is observed that studied suspensions display shear thickening/thinning flow behavior depending on their microstructure (the spatial distribution and arrangements of particles in continuous media) and associated changes in cluster sizes, which are controlled by the break down of densified clusters (due to the shear induced mechanical and hydrodynamical forces) and the interaction forces among particleparticle and particles-polymers (owing to physicochemical effects). The detailed evaluation of the experimental results indicates that the shear thickening phenomena in low volume fraction, anisotropic and flocculated systems can be mainly attributed to the increase in the effective volume fraction of particles due to both hydrodynamic and physicochemical forces.