Nihon Reoroji Gakkaishi
Online ISSN : 2186-4586
Print ISSN : 0387-1533
ISSN-L : 0387-1533
Volume 42 , Issue 4
Showing 1-7 articles out of 7 articles from the selected issue
ORIGINAL ARTICLES
  • Takafumi Toyoda, Ruri Hidema, Hiroshi Suzuki, Yoshiyuki Komoda
    2014 Volume 42 Issue 4 Pages 219-226
    Published: October 15, 2014
    Released: October 08, 2014
    JOURNALS FREE ACCESS
    Aluminum ammonium sulfate dodecahydrate (ammonium alum hydrate) slurry is a promising latent heat medium for high-temperature systems. However, there exist the significant issues with this medium at high temperature with respect to crystal agglomeration, growth, and sedimentation. Therefore, the effects of adding drag-reducing surfactants and poly vinyl alcohol (PVA) on the formation process of ammonium alum hydrates crystals under a controlled shear flow have been investigated in this study. In addition, in order to investigate the impact of the surface hydrophilicity and hydrophobicity of cooling walls on the crystal growth, a copper plate and a silica coated copper plate were used as the substrates of the wall. From the results, it was found that the mean crystal size of the ammonium alum hydrate decreased with increasing shear rates and with the addition of surfactants and PVA. In addition, the crystals on the silica coated copper plate were smaller than those on the copper plate without a coating. Thus, the addition of drag-reducing surfactants and PVA and use of a hydrophilic surface prevented the crystal agglomeration and crysal growth of the ammonium alum hydrate under a shear flow. Furthermore, the viscosity of each solution was also measured, as affected by the various additives and by crystal agglomeration and growth.
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  • Atsushi Matsumoto, Tadashi Inoue
    2014 Volume 42 Issue 4 Pages 227-233
    Published: October 15, 2014
    Released: October 08, 2014
    JOURNALS FREE ACCESS
    Dynamic viscoelasticity and birefringence of two poly(1-butyl-3-vinylimidazolium) based polymerized ionic liquids, PC4VICPFSI and PC4VINfO, are investigated by using hand-made shear and tensile rheo-optical apparatus for a further consideration of sub-Rouse mode in polymerized ionic liquids systems. Sub-Rouse mode spectrum for PC4VICPFSI whose counter anions is the same chemical structure as TFSI- and different shape showed the same component function as sub-Rouse mode for PC4VITFSI. On the other hand, sub-Rouse mode spectrum for PC4VINfO whose counter anions is the same ionic size as TFSI- but different chemical structure became sharper than that of PC4VITFSI. This result indicated that plasticization effect of counter anions would be more responsible for sub-Rouse mode.
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  • Yumi Matsumiya, Hiroshi Watanabe
    2014 Volume 42 Issue 4 Pages 235-244
    Published: October 15, 2014
    Released: October 08, 2014
    JOURNALS FREE ACCESS
    Cis-polyisoprene (PI) has the type-A dipole parallel along the chain backbone thereby exhibiting slow dielectric relaxation that reflects the global chain motion (end-to-end vector fluctuation). For linear PI probes having the molecular weights M1 in a range between 21.4× 103 and 179 × 103 (M1/Me = 4-36) and being blended with a longer PI matrix (M2 = 1.12 × 106), a recent dielectric experiment revealed that the probe relaxation is moderately retarded on blending and this retardation is enhanced with decreasing M1 in this range; cf. Matsumiya et al., Macromolecules, 46, 6067 (2013). Those dielectric data were analyzed within the context of the tube model to suggest that the probe relaxation in monodisperse bulk occurs through reptation along a partially dilated tube that wriggles in a fully dilated tube. However, this mechanism of relaxation is expected to vanish on a further decrease of M1 because the tube itself loses its sound meaning for small M1. This expectation was examined in this study. Dielectric and viscoelastic tests revealed that the retardation of the probe relaxation on blending becomes minor (though not negligible) on a decrease of M1 to 7.8× 103 (≈ 1.6Me), as expected.
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  • Navid P. Khabazi, Mohsen Aryan, Jalil Jamali, Kayvan Sadeghy
    2014 Volume 42 Issue 4 Pages 245-253
    Published: October 15, 2014
    Released: October 08, 2014
    JOURNALS FREE ACCESS
    In the present work, Sakiadis flow of a shear-thinning fluid obeying Harris rheological model is investigated analytically. Assuming that the flow is occurring at high Reynolds number, use will be made of the boundary layer theory to simplify the equations of motion. The equations so obtained are then reduced to a single fourth-order ODE using a suitable similarity variable. The homotopy analysis method (HAM) is used to solve the fourth-order nonlinear equation so obtained using the Mathematica software. The material parameters appearing in the Harris model are shown to be responsible for the lack of a self-similar solution, but fortunately the flow is shown to render itself to a local similarity solution. The results show that for the Harris model to represent shear-thinning fluids, the sign and magnitude of the material parameters appearing in this tricky rheological model should be carefully selected.
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  • Azusa Miyagawa, Shogo Nobukawa, Masayuki Yamaguchi
    2014 Volume 42 Issue 4 Pages 255-260
    Published: October 15, 2014
    Released: October 08, 2014
    JOURNALS FREE ACCESS
    Thermal expansion behavior and viscoelastic properties of antiplasticized polycarbonate (PC) are studied employing p-terphenyl (p-tPh) as an antiplasticizer. The rheological characterization reveals that the free volume fraction at the glass transition temperature and thermal expansion coefficient of the free volume in the rubbery region are unchanged by the p-tPh addition. However, the linear coefficient of thermal expansion in the glassy region is found to be reduced, which can be attributed to the reduction of free volume in the glassy state. Since the antiplasticized PC exhibits high modulus with a low thermal expansion coefficient, its suitability as a replacement for inorganic glasses will be considered.
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NOTE
  • Tadashi Inoue, Naoto Oba, Osamu Urakawa
    2014 Volume 42 Issue 4 Pages 261-264
    Published: October 15, 2014
    Released: October 08, 2014
    JOURNALS FREE ACCESS
    A simple calculation method to evaluate intrinsic viscosity from viscosity data at a finite concentration (i.e. without the extrapolation to zero concentration) is examined to clarify its applicability. The method, [η] = {2(ηsp-lnηr)}1/2/c, is based on Huggins and Fuoss-Mead plots. Here, ηsp and ηr are respectively specific viscosity and relative viscosity, and c is concentration. Its applicability was tested with published viscosity data for polystyrene and poly(α-methyl styrene) solutions. The method was found to work well for good solvents in the concentration regime c / c * ≤ 2, where c * is the overlapping concentration. On the other hand, for the case of θ solvents, the applicability of the method was very limited to low concentration of c / c * < 0.4, due to the viscosity enhancement by the entanglements.
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LECTURE
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