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Volume 31 (2003)
- Issue 5 Pages 287-
- Issue 4 Pages 185-
- Issue 3 Pages 119-
- Issue 2 Pages 79-
- Issue 1 Pages 3-
Volume 31, Issue 5
Displaying 1-7 of 7 articles from this issue
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Invited Article
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Lin Li, Qiqiang Wang, Yirong Xu2003 Volume 31 Issue 5 Pages 287-296
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSMethylcellulose is an associative polymer. Aqueous solutions of methylcellulose show the interesting thermoreversible gelation behavior that they gel upon heating and return to a liquid upon cooling. Thermally induced hydrophobic association and dissociation of methylcellulose in water explain the mechanism of thermoreversible gelation. The thermal analysis proves that the association of methylcellulose molecules in water is thermorevesible but the dissociation occurs at much lower temperatures than those for the association. The viscoelastic properties of methylcellulose aqueous solutions correlate excellently with the micro thermal results. The evolution of the gel elasticity Ge at a given gelling temperature (65 to 75°C) could be approximately expressed by Ge ˜ c2.56. At the same concentration, increasing of molecular weight of methylcellulose increases the heat absorbed during the sol-gel transition as well as Ge. While the addition of salts does not change the patterns of gelation and degelation of methylcellulose, the salts could shift the sol-gel transition to lower or higher temperatures from a salt-free methylcellulose solution, depending on the salt type.
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Howard See2003 Volume 31 Issue 5 Pages 297-303
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSA magneto-rheological suspension (MRS) is a particulate suspension which shows a dramatic increase in flow resistance upon application of an external magnetic field. The fundamental physical process is believed to be that the field induces polarization of each particle with respect to the carrier material, and the resulting interparticle forces cause aggregates of particles to form in the field direction. While recent years have witnessed the appearance of several applications using these tunable flow properties, optimal use of MRS technology is still hindered by our incomplete understanding of the underlying mechanisms. This paper surveys recent developments which have improved our understanding of several of the key issues governing the rheological behavior of MRS. In particular, experiments using small strain rheometry and oscillatory shear flow have given insights into the viscoelastic nature of the aggregates before they yield. A recent advance in modeling has been the two fluid continuum approach, which may help the establishment of a more general constitutive framework for MRS.
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Du Miao, Zheng Qiang, Yang Hong Mei2003 Volume 31 Issue 5 Pages 305-311
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSThe dynamic rheological behavior of polymer composites filled with particles has been an interesting topic in polymer research fields because of the challenging physical problems and the increasing technological applications behind. In this paper, recent progress in studies on the characteristic dynamic rheological response for polymer composites was reviewed, mainly depending on the results by the authors, including HDPE filled with conductive particle, PS filled with Sn-Pb alloy, LDPE filled with MMT, PMVS filled with ultrafine silica and PP filled with ultra-fine full-vulcanized powdered rubber. Based on the rheological measurements, some new fingerprints that responsed the evolution of morphology and strcutrure for these polymer composites were obtained. These new results provide guidelines for fabricating new composite materials.
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Original Article
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Seiji Shiromoto, Kiyohito Koyama2003 Volume 31 Issue 5 Pages 313-319
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSThe morphology change and viscoelastic behavior of polypropylene/polyethylene blend systems under shear flow was investigated. Polypropylene homo-polymer (PP-A), polypropylene block-copolymer including ethylene-propylene copolymer part (PP-B) and linear low density polyethylene (PE) were used for this study. The steady and dynamic viscoelasticities under shear flow were measured. Mix rule was not adapted for the rheological properties at long times. The relaxation modulus of PP-A and PP-B decreased as a function of the time, but that of both PP/PE blends showed 2-step relaxation mode. The swelling ratio of PP-A and PP-B increased according to the increase of shear rate. On the other hand, shear rate dependence of the swelling ratio of PP became small by addition of PE. The morphology of capillary strands after shear flow was observed by TEM. As a result, the morphology change of PP-B was small for wide range of shear rate. The droplets size was large and it strongly orientated to flow direction at low shear rate region for both PP/PE blends. Then, the size and orientation of droplets were reduced due to the increase of the shear rate. It was concluded that the swelling behavior of both PP/PE blends was affected by morphology change according to the shear rate.
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Seiji Shiromoto, Tarou Miyazawa, Kiyohito Koyama2003 Volume 31 Issue 5 Pages 321-327
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSThe relationship between uniaxial elongational viscosity and vacuum molding processability of the PP/PE blends were investigated. Propylene homo-polymer (PP) and 3 kinds of high pressure method low density polyethylene with different molecular weight (PE-A, PE-B, PE-C) were used. Materials were melt blended to the ratio of PP/PE=90/10, 80/20 and 70/30wt% for the experiments. The PP/PE blends showed strain hardening of uniaxial elongational viscosity, while PP showed no strain hardening. The strain hardening of PP/PE increased with increasing of the blend ratio of PE to PP, and the molecular weight of PE. The morphologies of PP/PE under uniaxial elongational flow were observed by TEM. For the samples with the lower molecular weight PE, the larger deformation of PE domain was observed. The deviation of thickness of the vacuum molding products decreased according to the increase of the strain hardening of PP/PE.
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Kazuyuki Shohara, Kousuke Uotani, Hideki Yamane2003 Volume 31 Issue 5 Pages 329-335
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSRheological and mechanical properties and particle dispersion state of silicone resin filled with various silica particles were investigated before and after crosslinking. Uncrosslinked resin filled with smaller particles at higher content showed higher storage modulus G' and complex viscosity |η*| at lower frequency region and a second plateau was observed. When the particle size is almost identical, particle with hydrophilic surface made G' and |η*| slightly higher. From those results, liquid matrix containing smaller particles at higher content has stronger three-dimensional structure. This structure seems to be stronger in the hydrophobic matrix filled in the hydrophilic particles. On the other hand, small hydrophobic particles increased the storage modulus E' of crosslinked resin at the rubbery region. These increases in E' at the rubbery region reflect the increases in the tensile modulus and strength of particle filled elastomers in the tensile test. These results suggested that the three-dimensional network structure formed with hydrophilic particles in hydrophobic matrix increased elastic character when the matrix is uncrosslinked. However, once matrix is crosslinked, adhesion between particles and matrix enhances the mechanical properties.
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Riwako Nakamoto, Ryoji Yasue2003 Volume 31 Issue 5 Pages 337-342
Published: 2003
Released on J-STAGE: April 17, 2004
JOURNAL FREE ACCESSFocusing on the particle size of gellan gum microgel fluid dispersion, we found that even with the same composition, the appearance and rheological characteristics of microgel fluid dispersion were different depending on the difference of particle size. Comparison among rheological characteristics indicated that the greater the particle size of microgel was, the larger the yield stress and shear stress during flowage were and that there was an appropriate correlation (r=0.97) between the particle size of microgel and the yield stress of fluid dispersion. It was observed that among microgel fluid dispersion samples having the same particle size, the less concentration of calcium ions added as crosslinker for double helix they had, the greater shear stress they showed. We considered it as an influence of interaction among microgel particles. We found that the control of the particle size of microgel fluid dispersion and the calcium ion concentration was effective as a method of controlling the properties of microgel fluid dispersion. Microgel particles with smaller size decrease the yield stress of fluid dispersion, deteriorating the dispersion stability of dispersoid. However, by including the dispersoid in microgel particles, we could prepare a product providing a compatibility between the product appearance and stability.
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