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Volume 35 (2007)
- Issue 5 Pages 227-
- Issue 4 Pages 179-
- Issue 3 Pages 119-
- Issue 2 Pages 59-
- Issue 1 Pages 1-
Volume 35, Issue 3
Displaying 1-7 of 7 articles from this issue
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Feature Article
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Hiroshi Kawakami2007 Volume 35 Issue 3 Pages 119-127
Published: 2007
Released on J-STAGE: September 14, 2007
JOURNAL FREE ACCESSIn the present article, results from our recent studies on effects of chemical crosslinks in epoxy glass subjected to large deformation and subsequent aging under strain are reviewed. Bis-A type epoxy monomer was cured with DDM to form a sample with a crosslinked network structure. The monomer was also polymerized with aniline to form another sample with an uncrosslinked linear molecular structure. First, change in birefringence in the course of elongation was measured, and the modified stress-optical rule was applied to the experimental results. For the crosslinked sample, both internal potential and entropy changed in a small strain range. On the other hand, for the linear molecular sample only internal potential increased in a small strain range. Another series of results was obtained through thermomechanical experiments with largely deformed specimens, and the obtained results indicated that chemical crosslinks forced more rubbery strain to recover at temperatures below Tg. From these studies it was proposed that chemical crosslinks in epoxy glass enhance cooperativity between molecular motions taking place in deformation as well as in subsequent retardation process. Such an effect of chemical crosslinks was also observed in the crosslinked sample under the state of aging under strain.View full abstractDownload PDF (456K)
Original Articles
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Alfeus Sunarso, Takehiro Yamamoto2007 Volume 35 Issue 3 Pages 129-136
Published: 2007
Released on J-STAGE: September 14, 2007
JOURNAL FREE ACCESSIn our previous work, we have improved the reversible network model proposed by Cifre and co-workers, and performed a Brownian dynamics simulation to investigate the capability of the model in predicting the shear and elongational properties of non-associative polymeric fluids. In the present work, the capability of the improved model in predicting the rheological properties of associative polymeric fluids is presented. Similar to that for non-associative polymers, substitution of Hookean connection force with FENE connection force is required for better prediction in shear and elogational properties of associative polymer. In shear flow, the model with FENE connection force predicts shear thickening in the shear viscosity, and the peak of the shear thickening depends strongly on the maximum extension parameter. The responses in the first normal stress difference show that the model is able to predict relatively fast growth at low shear rates and relatively slow growth at high shear rates. In the elongational flow, the model is able to predict elongational viscosity with strain thickening at low strain rate followed by strain thinning or constant viscosity at moderate and high strain rates depending on various model parameters.View full abstractDownload PDF (467K) -
Shinji Toga, Tomiichi Hasegawa, Takatsune Narumi2007 Volume 35 Issue 3 Pages 137-145
Published: 2007
Released on J-STAGE: September 14, 2007
JOURNAL FREE ACCESSFluctuation of flows through a small orifice has been measured for water and two kinds of colloidal dispersions including fine particles about 100 nm in diameter with 1 % volume fraction in water. In this volume fraction, a surface potential of the particles is composed of an electrostatic repulsion and a van der Waals attraction and it affects flow properties. Experiments clarify that a specific flow instability occurs for water at the Reynolds number about 60, and the dispersion of polystyrene particles having strong repulsion increases the specific flow instability in low salt concentrations(LSC) but makes it disappear in high salt concentrations(HSC). Meanwhile, it is found that the dispersion of silica particles having strong attraction is stable in flows except the specific flow instability in LSC but it suppresses the specific flow instability in HSC as in the case of polystyrene particles. Criterion whether the orifice flow is stable or not is predicted by comparison of the second minimum location of the surface potential and the mean surfaces distance of the particles.View full abstractDownload PDF (1050K) -
Effect of Nonlinearity Strength in Chain Tension on Shear-Thickening of Associating Polymer NetworksTsutomu Indei2007 Volume 35 Issue 3 Pages 147-153
Published: 2007
Released on J-STAGE: September 14, 2007
JOURNAL FREE ACCESSThe shear thickening phenomena observed in telechelic associating polymers are studied on the basis of the transient network theory. We investigate how the nonlinearity of the tension along the middle chains affects the stationary shear viscosity of the network under the following conditions: (i) the dissociation rate of the end chains from the network junctions is coupled to the middle-chain tension, and (ii) the generation rate of the chain in a loop conformation is enhanced by the middle-chain tension. A strong nonlinearity in the tension can cause shear thickening if the dissociation rate of the end chains is weakly coupled to the tension. If the nonlinearity of the tension is too strong, however, the dissociation rate is strongly coupled to the tension; moreover, dangling chains tend to be transformed into loop chains rather than bridge chains, thereby leading to shear thinning. The latter effect on the condition for thickening is shown to be small. Thus, the thickening condition is mainly determined by the balance between the nonlinearity strength in the middle-chain tension and the coupling intensity between the dissociation rate and the middle-chain tension.View full abstractDownload PDF (447K) -
Yumi Matsumiya, Tadashi Inoue, Hiroshi Watanabe, Shinichi Kihara, Masa ...2007 Volume 35 Issue 3 Pages 155-161
Published: 2007
Released on J-STAGE: September 14, 2007
JOURNAL FREE ACCESSDielectric measurement was conducted for cis-polyisoprene (PIP) in carbon dioxide (CO2) at high pressures. CO2 is dissolved in PIP more with increasing pressure, and this dissolution is expected to affect the chain dynamics. In our experimental window, the PIP chains having type-A dipoles parallel along their backbone exhibited the dielectric dispersion reflecting their global motion. This dispersion shifted to higher frequencies with increasing CO2 pressure. Time - CO2 pressure superposition was found to hold well, which suggests that the global motion of the chain is accelerated by CO2 without any heterogeneity in space and along the chain backbone. The vertical shift factor (intensity shift factor) for this superposition gave the CO2 concentration in PIP. The plasticizing capability of CO2 evaluated from the horizontal shift factor (frequency shift factor) was found to be a little larger than that of tetradecane in the same range of concentration. No peculiarity was found for plasticizing ability of CO2 even in the supercritical state (at a pressure of 10 MPa).View full abstractDownload PDF (581K) -
Nori Yoshihara2007 Volume 35 Issue 3 Pages 163-168
Published: 2007
Released on J-STAGE: September 14, 2007
JOURNAL FREE ACCESSThe structure and mechanical properties of three kinds of polyether-ester elastomers were studied. The crystallization speed of the elastomer based on poly(butylene terephthalate) (PBT) as hard segment was higher than that of the elastomer based on poly(ethylene terephthalate) (PET) from the molten state. The elastomer based on higher molecular weight (Mn) of soft segment had higher crystallization speed than the elastomer based on lower molecular weight of soft segment. All of them had spherulitic structures in the molded articles. The spherulitic structure could be elastically elongated and retracted. The strain of the spherulitic structures is lower than that of affine deformation. The shape of the spherulitic structures was not broken under the extension ratio of 6 but the internal structure was changed with high strain. In a rubber-like state their modulus rose up in the order of PET-Mn2000, PBT-Mn2000 and PBT-Mn1000. However, at temperatures higher than 165°C their modulus fell in the order of PET-Mn2000, PBT-Mn2000 and PBT Mn1000 due to the effect of the melting point of hard segment. In the transition state PET-Mn2000 and PBT-Mn2000 revealed higher modulus than PBT-Mn1000 which did not contain crystallized soft segments. Their Mooney-Rivlin plots suggested effects of strain hardening at the higher extension ratio above the value of 7.View full abstractDownload PDF (1666K)
Note
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Yoshiaki Takahashi, Masayo Sato, Shinichi Kitade, Ichiro Noda2007 Volume 35 Issue 3 Pages 169-171
Published: 2007
Released on J-STAGE: September 14, 2007
JOURNAL FREE ACCESSViscoelastic properties of immiscible polymer blends consisting of polystyrene and poly(2-vinylpyridine), both of which have almost the same viscoelastic properties are studied under steady shear flow in linear and non-linear regions for the viscoelastic properties of components. It was observed that shear rate dependence of shear viscosity of blend samples was the same as those of component homopolymers, implying that the excess shear stress is proportional to the shear rate in the linear and non-linear regions for component polymers. It was also observed that the excess first normal stress difference of the blends was also proportional to the shear rate. It is concluded that the scaling relations between the excess stresses and the shear rate observed for binary immiscible polymer blends consisting of components with similar Newtonian viscosities can be extended into the higher shear rate regions where the components show similar non-linear viscoelastic behaviors.View full abstractDownload PDF (336K)
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