Nihon Reoroji Gakkaishi
Online ISSN : 2186-4586
Print ISSN : 0387-1533
ISSN-L : 0387-1533
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Volume 28, Issue 3
Displaying 1-8 of 8 articles from this issue
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  • Uniaxial Extensional Flow and Thermoformability of PMMA Melts with Very High Molecular Weight Component
    Koji Ogura, Masaoki Takahashi
    Article type: Article
    2000 Volume 28 Issue 3 Pages 99-103
    Published: September 15, 2000
    Released on J-STAGE: October 27, 2000
    DOIhttps://doi.org/10.1678/rheology.28.99
    JOURNAL FREE ACCESS
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    Uniaxial extensional flow behavior and processability in thermoforming are studied for poly (methyl methacrylate) samples with a very high molecular weight component in order to propose a method for predicting the processability using a small amount of samples. In uniaxial extensional flow, strain-hardening behavior is observed. Thickness distribution of molded samples in the thermoforming at 160°C is more uniform for the samples which exhibit the stronger strain-hardening. It is found that the strain-hardening behavior is controlled by entanglements between the high molecular weight component polymers. The degree of strain-hardening is correlated with the number of these entanglement points and the polydispersity index Mz/Mw.
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  • Viscoelastic Fluid in the Flow in Half-Spherical Gap
    Hiroshi Yamaguchi, Masatoshi Morishita
    Article type: Article
    2000 Volume 28 Issue 3 Pages 105-112
    Published: September 15, 2000
    Released on J-STAGE: October 27, 2000
    DOIhttps://doi.org/10.1678/rheology.28.105
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    Flow of viscoelastic fluid contained between a stationary outer sphere and a rotating inner hemisphere is studied experimentally. In the present investigation, relatively low-concentration polyacrylamide-water solutions are used as viscoelastic fluid, and for the sake of comparison glycerin-water solutions are used as the Newtonian fluid. In experiments, measurements of the rotational torque and thrust are carried out. Various transition phenomena of flow modes that are unique to viscoelastic fluids are investigated by flow visualization for a wide range of rotational Reynolds numbers.
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  • Effect of Electric Double Layer on Viscoelastic Behavior of Highly Concentrated Suspension
    Misao Horigome, Makoto Yada
    Article type: Article
    2000 Volume 28 Issue 3 Pages 113-117
    Published: September 15, 2000
    Released on J-STAGE: October 27, 2000
    DOIhttps://doi.org/10.1678/rheology.28.113
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    Experimental results on rheological behaviors of highly concentrated suspensions are presented. Suspensions of acryl-styrene copolymer particles with radius 45 nm dispersed in water were used as samples. Rheological properties were measured at particle volume fractions φ ranging from 0.177 to 0476. The rheological data were rescaled using the effective volume fraction φeff calculated from the effective radius estimated as a sum of the Debye length and the particle radius. In the range of φeff lower than the random close packing volume fraction(0.63), rheological behaviors of suspensions gave good agreement with those of ideal suspensions of rigid spheres. This shows that the Brownian contribution is the origin of the linear viscoelastic behavior in lower φ eff range. In the range of φeff higher than 0.63, the longest relaxation time and the activation energy rapidly increased with an increase in φeff, and the vertical shift factor diverged from estimated values of ideal suspensions. These results suggest that restraint of neighboring particles affects the Brownian motion, and furthermore, repulsive force induced by overlapping of electric double layers affects the viscoelastic behavior.
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  • A Study on Thermally Stimulated Current Behaviors of Liquid Crystal/Polymer Composite Films and Liquid Crystal/Monomer Mixtures
    Makoto Yada, Misao Horigome, Hidetoshi Nakada, Masanao Hayashi, Toru F ...
    Article type: Article
    2000 Volume 28 Issue 3 Pages 119-125
    Published: September 15, 2000
    Released on J-STAGE: October 27, 2000
    DOIhttps://doi.org/10.1678/rheology.28.119
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    Thermally stimulated current(TSC) behaviors of liquid crystal(LC)/polymer composite films and LC/monomer mixtures have been investigated. The composite films are formed by the photo-polymerization induced phase separation process. The samples used were mixtures of the fluorinated liquid crystals having tolane linking group and the diacrylate monomer, and the composite films after photo-polymerization. In TSC curves of the liquid crystal/monomer mixtures with 65-85mol% of LC fraction, 3 kinds of peaks were observed at -48(peak A), -55(peak B), and -62°C(peak C). The peak A was assigned as the melting point of the monomer-rich phase and the peak C as T g of the liquid crystalline phase, whereas there is no clear-cut explanation for the peak B. TSC curves of LC/polymer composite films showed a tendency similar to the LC/monomer mixtures.
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  • Viscoelastic Behavior of Bimodal Ideal Suspensions
    Toshiyuki Shikata, Hirokazu Niwa
    Article type: Article
    2000 Volume 28 Issue 3 Pages 127-135
    Published: September 15, 2000
    Released on J-STAGE: October 27, 2000
    DOIhttps://doi.org/10.1678/rheology.28.127
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    We examined the viscoelastic behavior of ideal suspensioncs consisting of spherical particles with hard-core potential between them. Unimodal ideal suspensions showed viscoelasticity with relaxation times proportional to the cube of the particulate radius. Bimodal ideal suspensions with a ratio of particulate radii below 4 had viscoelastic properties similar to those of unimodal ideal suspensions, of which the relaxation times were proportional to the product of the average particulate radius and the average of the particulate radius squared. However, bimodal ideal suspensions with a ratio greater than 5 showed two distinct relaxation times. The fast relaxation time was related to the motion of smaller particles and the slow relaxation time was related to that of larger particles. The ratio of 5 should be a criterion whether or not the motion of two types of particles can be averaged into one set of modes with an average relaxation time. A model for predicting frequency dependency of storage and loss moduli for bimodal ideal suspensions with the ratio of particle radii greater than 5 was proposed. Agreement between the frequency dependency of the model and the experimental data was quite good. Moreover, essential rheological parameters such as zero-shear and high frequency limiting viscosities were reasonably predicted by the model.
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  • Measurement of Interfacial Tension between Polymer Liquids : Pendant Drop, Improved Imbedded Fiber Retraction and Steady Shear Flow Methods
    Rika Hayashi, Masaoki Takahashi, Hideki Yamane
    Article type: Article
    2000 Volume 28 Issue 3 Pages 137-142
    Published: September 15, 2000
    Released on J-STAGE: October 27, 2000
    DOIhttps://doi.org/10.1678/rheology.28.137
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    The interfacial tension between a poly (isobutylene) (PIB) and a poly (dimethylsiloxane) (PDMS) was obtained by an improved imbedded fiber retraction method from the observation of the PDMS (or PIB) droplet shape in the PIB (or PDMS) matrix after application of the step shear strain. The interfacial tension was also obtained from the observation of the PDMS (or PIB) droplet shape during the steady shear flow. We compared the values of interfacial tension obtained by these methods with the value determined by the pendant drop method. It was found that these values agree fairly well when the viscosity ratio of the droplet to the matrix is around unity.
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  • On the Steady Shear Viscosity of Coagulated Suspensions
    Motoyoshi Kobayashi, Yasuhisa Adachi, Setsuo Ooi
    Article type: Short Communications
    2000 Volume 28 Issue 3 Pages 143-144
    Published: September 15, 2000
    Released on J-STAGE: October 27, 2000
    DOIhttps://doi.org/10.1678/rheology.28.143
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  • [title in Japanese]
    [in Japanese]
    Article type: Correspondence
    2000 Volume 28 Issue 3 Pages 145
    Published: September 15, 2000
    Released on J-STAGE: October 27, 2000
    DOIhttps://doi.org/10.1678/rheology.28.145
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