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Volume 33 (2005)
- Issue 5 Pages 223-
- Issue 4 Pages 161-
- Issue 3 Pages 113-
- Issue 2 Pages 61-
- Issue 1 Pages 1-
Volume 33, Issue 3
Displaying 1-6 of 6 articles from this issue
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Feature Articles
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Michio TokuyamaArticle type: Feature Article
2005 Volume 33 Issue 3 Pages 113-123
Published: 2005
Released on J-STAGE: October 29, 2005
JOURNAL FREE ACCESSThe liquid-glass transition for colloidal suspensions of hard spheres is discussed from a new theoretical point of view. The important role of the hydrodynamic interactions between colloids near the glass transition is pointed out. Two kinds of computer simulations are also performed to verify such an important role. Thus, those interactions are shown to be indispensable to explain the experimental data near the colloidal glass transition.View full abstractDownload PDF (937K) -
Nobuji Maeda, Yoji Suzuki2005 Volume 33 Issue 3 Pages 125-133
Published: 2005
Released on J-STAGE: October 29, 2005
JOURNAL FREE ACCESSElectrostatic repulsive force among human red blood cells (RBCs) was observed by macromolecules-induced RBC aggregation and RBC flow behavior in narrow tube, by reducing the sialic acid content of RBCs with neuraminidase. The electrophoretic mobility of the RBCs was proportional to the sialic acid content. (1) When the sialic acid content was reduced, the RBC aggregation observed with a low shear rheoscope was enhanced with fibrinogen (MW=340,000), Ig G (MW=160,000) or Dextran T-70 (MW=70,400), but did not without the macromolecules. In coexistence of normal cells, sialic acid-reduced cells settled significantly faster, possibly due to their preferential aggregation by the macromolecules. (2) Sialic acid-reduced RBCs accumulated more to flow axis in narrow tube (20-50 μm in inner diameter), especially at acidic pH, as evaluated by the thickness of marginal cell-free layer using an image processor. The thickness was further increased with Dextran T-70 due to the RBC aggregation. Conclusively, electrostatic repulsive force among RBCs provided by sialic acid is important for understanding hemorheological behavior of the RBCs and circulatory disturbances in various diseases.
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Original Articles
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Alfeus Sunarso, Takehiro Yamamoto, Noriyasu Mori2005 Volume 33 Issue 3 Pages 135-140
Published: 2005
Released on J-STAGE: October 29, 2005
JOURNAL FREE ACCESSThe flow of polymer melt in contraction channels with cylindrical barriers was numerically simulated. A commercial LDPE melt was considered, and the rheological property of the melt was represented using the Extended Pom-Pom model (XPP). The simulation was performed with various barrier configurations, and the effects of the barriers were investigated extensively in relation to the efforts to clarify the phenomenon of melt fracture mitigation by the addition of filter or porous medium. It can be observed that the addition of barriers modifies significantly the flow fields in the region near the contraction. Investigation of the elongation stress shows that the addition of barriers increases the stress in the region near the contraction, but decreases the elongation rate and elongation stress in the region at the upstream of the contraction and induces the undershoots of elongation rate and elongation stress in the region at the downstream of the contraction. With the increase in Weissenberg numbers, these effects are more significant for the channels with two barriers as compared to that with single barrier. The reduction of elongation rate and elongation stress should play an important role in the mitigation of the upstream instability, which in turn mitigates the gross melt fracture.
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Akinari Minegishi, Akihiro Nishioka, Tatsuhiro Takahashi, Yuichi Masub ...2005 Volume 33 Issue 3 Pages 141-144
Published: 2005
Released on J-STAGE: October 29, 2005
JOURNAL FREE ACCESSA novel polystyrene(PS) with an incorporation of a small mass fraction of styrene-butadine-styrene(SBS) and dicumyl peroxide(DCP) has been developed to enhance strain-hardening significantly under elongational flow. Here, strain-hardening is defined as steep increase of elongational viscosity at large strain which deviates from linear viscoelastic curve. The content of SBS was in a range from 1wt% to 10wt%, and the content of DCP was in a range from 0.01wt% to 0.1wt%. Pure PS at 180 °C did not exhibit any strain-hardening. Whereas, significant enhancement of strain-hardening was observed for PS blended only 1wt% SBS and 0.1wt% DCP. The magnitude of strain-hardening (SH) was over 10 up to Hencky strain of 3. Note that the parameter, SH, is defined as elongational viscosity at large strain to linear viscoelastic envelope at the same time. Enhancement of strain-hardening was in the order of SBS content and DCP content. The magnitude of strain-hardening(SH) for PS/SBS/DCP(SH~70 at the maximum) was much more remarkable than that of any other PS such as PS/UHMW-PS and branched PS reported before(SH<10). This is a new method to control elongational rheology of PS and has advantages over conventional ways in terms of its easier process than other methods such as introducing long-chain branching and high molecular weight in postreactor.
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Hong-Phuc Nguyen, Kiyotaka Ishihara, Hiroshi Suzuki, Yasuo Kawaguchi, ...2005 Volume 33 Issue 3 Pages 145-150
Published: 2005
Released on J-STAGE: October 29, 2005
JOURNAL FREE ACCESSThe biaxial extensional characteristics of a cationic surfactant solution system showing an effective drag reduction in pipe flow have been studied by using two opposed nozzle devices. Aqueous solutions of cationic surfactant, oleylbishydroxyethylmethylammonium chloride, at the concentrations varied from 250 to 1,000 ppm with sodium salicylate, which ionized to counter-ion in an aqueous solution, of which molar ratio to surfactant was set at 1.5, were tested. Especially, time characteristics of extensional stress were focused in wide ranges of surfactant concentration and extensional rate. From the results, the apparent extensional viscosity is found to depend on the extensional rate and on the surfactant concentration. For the extensional rate dependency, the extensional viscosity behavior is classified into four regions. This characteristic is considered to be caused by the formation and the deformation of the surfactant rod-like micellar network structure. In each region, the build-up and relaxation times are not strongly affected by the concentration of the surfactant. On the other hand, the build-up time decreases with a gradient of -1 in a double logarithm plot to the extensional rate, while the relaxation time decreases weakly with the extensional rate. The former fact indicates the micellar network formation occurs due to the collision of surfactant micelles. It is also found that two relaxation processes exist for the extensional flow cases. The shorter or the longer relaxation time takes almost the same value as each value corresponding to that for the shear flow release condition. This indicates the network structure size formed in the biaxial extensional flow takes almost the same as that in the shear flow.
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Note
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Hiromasa Adachi, Teruo Hasegawa2005 Volume 33 Issue 3 Pages 151-153
Published: 2005
Released on J-STAGE: October 29, 2005
JOURNAL FREE ACCESSFor evaluation of thermal endurance in foamed plastics, temperature and time dependence of compression dynamic modulus of four flexible polyurethane foams was investigated by dynamic viscoelastic measurements. In an interested temperature range, compression dynamic modulus of each polyurethane foams lessened gradually with time, presumably due to thermal degradation of foam skeletons accompanying deterioration in bending stiffness of the skeleton. Logarithm of time t, at which the compression dynamic modulus came to be 90%, 80% and 50% of its initial value at the beginning of the dynamic measurement, has been found to be a linear function of reciprocal temperature T -1. Thermal endurance characteristics of flexible polyurethane foams can be evaluated from the linear relations between T-1 and logarithm of time t at which the compression dynamic modulus came to be 50% of its initial value.
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