Nihon Reoroji Gakkaishi
Online ISSN : 2186-4586
Print ISSN : 0387-1533
ISSN-L : 0387-1533
Volume 20 , Issue 3
Showing 1-7 articles out of 7 articles from the selected issue
  • Hideaki ISHIHARA, Seishu HAYASHI, Hiroshi YASUDA
    1992 Volume 20 Issue 3 Pages 109-117
    Published: September 20, 1992
    Released: November 20, 2012
    JOURNALS FREE ACCESS
    There are many rheological problems in melt spinning process. They can be classified into two categories i.e., the problems in shearing flow and those in extensional flow. The former is concerned with extrusion of molten PET (polyethylenetere-phthalate) through spinneret orifices. Bagley's plots showing the relationship of pressure drop to L/D of orifice were done to obtain the end correlation in the capillary flow of PET. By using this end correction values, the relaxation time of molten PET was estimated to be around 2×10-3 sec under some assumptions.
    With regard to the problems in the extensional flow three typical and important examples were shown from both experimental and theoretical aspects.
    (1) Fine denier filament spinning for obtaining fibers with less than about 10 μm in diameter is a challengeable theme in the meaning of a conflict with extensional flow instability, so called draw resonance phenomenon. To solve this difficulty, it can be suggested that optimal spinneret orifice design will be required for instance.(2) High speed spinning is a process of stress-induced crystallization of PET. Dependence of spinning behaviors such as neck-like deformation and mechanical/structural properties on PET molecular weight was investigated. Crystallization of higher molecular weight PET was found to occur at lower spinning speed compared with that of lower one. (3) Air jet melt spinning for multifilament system was investigated both theoretically and experimentally. Computation results showed a good agreement with experimental ones in terms of the stretching speed in ejector. Birefringence values of as-spun fibers can be estimated by using computed outputs.
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  • Hideaki ISHIHARA, Tetsuo KOTANI, Seishu HAYASHI
    1992 Volume 20 Issue 3 Pages 118-124
    Published: September 20, 1992
    Released: November 20, 2012
    JOURNALS FREE ACCESS
    Dry spinning behavior of the segmented polyurethane-urea elastomer/solvent binary system was studied theoretically and experimentally. Computer simulation was carried out by solving the partial differential equations numerically for discussing the structure and properties of as-spun fibers. Spinning stress computed at the take-up point was found to be useful for describing the segmental orientations and the aggregate structure of the hard segment in relation to the mechanical properties such as elastomeric character of the fibers.
    With increase of the spinning stress, orientation of the hard segment becomes higher. Orientation of the soft segment, however, is almost random regardless of spinning stress, resulting in the origin of the elastomeric character. Dependence of the spinning stress on the hydrogen bond concentration of urea group suggested that the aggregate structure of the hard segment was smaller when the fiber was spun at a higher spinning stress.
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  • Yasufumi OTSUBO, Robert K. PRUD'HOMME
    1992 Volume 20 Issue 3 Pages 125-131
    Published: September 20, 1992
    Released: November 20, 2012
    JOURNALS FREE ACCESS
    The flow behavior of oil-in-water emulsions is examined as a function of the volume fraction of dispersed drops, drop size, and viscosity ratio of internal to external phases. The results are interpreted in terms of internal circulation, deformation, and breakup of drops. At low volume fractions, the viscosity decreases with increasing shear rate and becomes constant at high shear rates. The Newtonian viscosity is independent of drop size. The viscosity in the pseudoplastic region increases with decreasing drop size. A change in drop size at constant volume fraction causes a horizontal shift in the viscosity versus shear rate curve. As the viscosity ratio decreases, the relative viscosity at a given volume fraction is reduced because hydrodynamic forces cause internal circulation which reduces the velocity perturbations outside drops. At high volume fractions where a network of thin liquid films is formed, the change in drop size leads to a vertical shift of the viscosity curve. The flow behavior in highly concentrated emulsions is governed by total interfacial area. When the deformation and breakup of drops occur at high shear rates, the emulsions show pseudoplastic flow
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  • Shoichiro YANO, Bengt STENBERG, Per FLINK
    1992 Volume 20 Issue 3 Pages 132-140
    Published: September 20, 1992
    Released: November 20, 2012
    JOURNALS FREE ACCESS
    The mechanical properties of natural rubber composites filled with cellulose short fibers were investigated with respect to fiber concentration and fiber orientation. Strong anisotropy caused by the fiber orientation was observed in the mechanical properties at high fiber loading. The ultimate tensile strength in the longitudinal direction to the fiber orientation had a minimum at Vf=12.5%, while the transverse strength decreased with Vf values. The logarithmic elongation at break decreased linearly with Vf, and the transverse elongation was higher than the longitudinal elongation. The modulus of the composite increased with fiber concentration, with semi-empirical equation E=k/{1+[Vm/(1-Vm0.5)]} being valid for the transverse direction and the longitudinal direction at lower fiber loading. The longitudinal modulus was much higher than the transverse modulus. In order to improve adhesion between the fibers and matrix, polyallylacrylate was grafted on cellulose fibers, but grafting was ineffective on the mechanical properties of the composite. The dynamic viscoelastic properties of the natural rubber composite was also investigated. The dynamic modulus, E′, increased with increasing amounts of fiber concentration above the glass transition temperature. The loss modulus, E″, had a peak at about -36°C, which shifted to higher temperatures with increasing amounts of mixed fibers. The activation energy for glass transition of the composites was calculated as 198.6-228.6 kJ/mol, depending on fiber concentration for the longitudinal direction. The dynamic viscoelasticity in the transverse direction to the fiber orientation was not affected by filled fibers and the activation energy was 187.3 kJ/mol, approximately the same value as for unfilled rubber vulcanizate.
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  • Takaaki HATTORI, Toshikazu TAKIGAWA, Toshiro MASUDA
    1992 Volume 20 Issue 3 Pages 141-145
    Published: September 20, 1992
    Released: November 20, 2012
    JOURNALS FREE ACCESS
    Uniaxial and biaxial elongational flow behavior of low density polyethylene (LDPE)/polystyrene (PS) blends (LDPE/PS=2/1) with and without 5 wt% styrene-ethylene-propylene block copolymer (SEP) was studied. In these blends, LDPE was the matrix phase and PS was the dispersed phase. Measurements of the uniaxial elongational viscosity η+(t, ε) and the biaxial elongational viscosity ηB+(t, ε) were made using a Meissner-type uniaxial elongational rheometer and a lubricated-squeezing type equibiaxial rheometer, respectively.
    In the linear region, the relation between the transient shear viscosity η+(t) and the transient elongational viscosity, which were predicted by 3-dimensional linear Maxwell model, i.e. EE+(t)=3η+(t) and ηB+(t)=6η+(t), did not hold well. This may be attributed to a volumetric resistance against the deformation perpendicular to the elongational direction because of the existence of PS particles. In the long-time region, a difference of ηE+(t, ε) between blends with and without SEP was observed. In the case of uniaxial elongational flow, it may be presumed that a contribution of the deformation of PS domains to the elongational flow behavior has to be taken into account when the elongational strain is large.
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  • Masahiko OKUMURA, Mitsuru NAGASAWA
    1992 Volume 20 Issue 3 Pages 146-152
    Published: September 20, 1992
    Released: November 20, 2012
    JOURNALS FREE ACCESS
    The birefringence in injection molds of non-crystalline linear polymers arises from two different kinds of deformation; one incorporated with the change of intersegmental distance and one with the deformation of molecular conformation. Their contributions to birefringence were separately observed in injection molded polystyrene.
    The birefringence originating from the molecular-conformational deformation was compared with computer simulation results, in which the rheology constitutive equation of Leonov was employed to calculate the shear and the normal stresses.
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  • Hirotsugu YOSHIDA, Hajime SHOHI, Yoichi MIKAMI
    1992 Volume 20 Issue 3 Pages 153-156
    Published: September 20, 1992
    Released: November 20, 2012
    JOURNALS FREE ACCESS
    Viscoelastic properties of novel 3-arm star poly (isobutyl vinyl ether) (PIBVE) were investigated and compared with those of linear PIBVE. In a high molecular weight (M) region, the zero-shear viscosity η0 increased with M more rapidly for 3-arm star PIBVE than for linear PIBVE. The steady-state compliance Je0 tended to increase with M for 3-arm star PIBVE, but appeared to be independent of M for linear PIBVE. These linear viscoelastic features of 3-arm star PIBVE are qualitatively the same as those for other star polymers investigated so far. In a nonlinear viscoelastic regime, the Cox-Merz rule held for both 3-arm star and linear PIBVEs. In a vicinity of an onset of decrease in the shear viscosity η with shear rate γ, relations between the reduced viscosity η/η0 and the reduced shear rate γJe0η0 agreed fairly well for 3-arm star and linear PIBVE samples examined.
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