Nihon Reoroji Gakkaishi

Original Articles

Viscosity Prediction of Dense Slurries with Agglomerative Coal Particles

Hiromoto Usui

Article type: Article
2001 Volume 29 Issue 2 Pages 71-76
Published: 2001
Released on J-STAGE: June 14, 2003

DOIhttps://doi.org/10.1678/rheology.29.71

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The shape of suspended particle affects the rheological characteristics of slurries. The sphericity of coal particles depending on the particle diameter was measured by means of an image processing instrument. An algorithm to predict the maximum packing volume fraction with non-spherical particles was proposed. The maximum packing volume fraction combined with Simha's cell model and Usui's suspension rheology model was used to predict the slurry viscosity. It was certified that the maximum packing volume fraction for non-spherical particles can be successfully used to predict non-Newtonian slurry viscosity.

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Rheo-dielectric Behavior of Carbon Black Suspensions

H. Watanabe, Y. Matsumiya, M. Kakiuchi, Y. Aoki

Article type: Article
2001 Volume 29 Issue 2 Pages 77-80
Published: 2001
Released on J-STAGE: June 14, 2003

DOIhttps://doi.org/10.1678/rheology.29.77

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Rheo-dielectric behavior was examined for suspensions of two types of carbon black (CB) particles in varnish. For one type of CB particles having plain carbon surfaces, an agglomerated network was fully developed to exhibit low-frequency elasticity (under small strains) and high electrical conductance. This conductance decreased significantly under flow, reflecting flow-induced rupture of the network structure. This rheo-dielectric change well corresponded to the pseudo-plastic, non-Newtonian behavior of the viscosity η. In contrast, for the other type of CB particles having oxidized carbon surface, only fragmented aggregates were formed. Correspondingly, this CB exhibited just moderate rheo-dielectric changes and weak nonlinearities in its η. These results demonstrated the usefulness of the rheo-dielectric method for detecting the connectivity of the network composed of conductive CB particles.

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Viscous Fingering of Non-Newtonian Fluids in a Rectangular Hele-Shaw Cell

Takehiro Yamamoto, Hiroo Kamikawa, Hiromitsu Tanaka, Kiyoji Nakamura, ...

Article type: Article
2001 Volume 29 Issue 2 Pages 81-87
Published: 2001
Released on J-STAGE: June 14, 2003

DOIhttps://doi.org/10.1678/rheology.29.81

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Non-Newtonian viscous fingering in a rectangular Hele-Shaw cell was studied. Compressed air was injected into the cell filled with a more viscous fluid. For the more viscous fluids, glycerin was used as a Newtonian fluid, and aqueous solutions of carboxymethylcellulose (CMC) and polyacrylamide (PAA) were used as non-Newtonian fluids. The growth and the structure of viscous fingers were analyzed. The shear-thinning viscosity of the polymer solutions made the 'shielding' effect strong. When the 'shielding' appeared strongly, the fingers formed a branched structure. In the PAA solution, the change in the finger pattern, a sudden growth of thin fingers from a wide finger-tip, was observed. It was supposed that stretch-thickening elongational viscosity and the shear-thinning viscosity were related to this phenomenon.

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Unstable Slit Flows of Liquid Crystalline Solution of Hydroxypropylcellulose

Noriyasu Mori, Masatada Shindo, Tsutomu Takahashi, Kiyoji Nakamura

Article type: Article
2001 Volume 29 Issue 2 Pages 89-94
Published: 2001
Released on J-STAGE: June 14, 2003

DOIhttps://doi.org/10.1678/rheology.29.89

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Unstable flows of liquid crystalline polymers in slit flow cells are studied using a 50wt% aqueous solution of hydroxypropylcellulose. The wavy texture pattern is observed in the downstream region far from the entrance of the flow cell regardless of the geometry of cell entrance. The cell thickness significantly affects the structure of the wavy texture, and its wavy length increases with increasing cell thickness. Furthermore, the dichroism measurement is carried out to examine the development of molecular orientation in the flow cell with an abrupt expansion entry. In the region where the wavy texture exists, the molecules align in the direction of the flow on the average over the cell thickness.

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Note

Compression Modulus of Hard Polyurethane Foams after Artificial Destruction of Cell

Hiromasa Adachi, Teruo Hasegawa

Article type: Note
2001 Volume 29 Issue 2 Pages 95-98
Published: 2001
Released on J-STAGE: June 14, 2003

DOIhttps://doi.org/10.1678/rheology.29.95

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In this study, the compression modulus of some hard polyurethane foams before and after artificial destruction of cell was determined by the static compression tests and the dynamic viscoelastic measurements in compression mode. In the static compression tests, there are yield regions in foams before destruction of cell but no yield region in foams after destruction of cell. It was confirmed that cells are destroyed gradually over the yield region in foams before destruction of cell. In comparison of the static compression modulus by the static compression tests with the dynamic compression modulus by the dynamic viscoelastic measurements, the dynamic compression modulus is larger than the static compression modulus in foams before destruction of cell, but the dynamic compression modulus is smaller than the static compression modulus in foams after destruction of cell because of the non-linear phenomenon by buckling.

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