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Volume 10 (1982)
- Issue 4 Pages 147-
- Issue 3 Pages 103-
- Issue 2 Pages 51-
- Issue 1 Pages 1-
Volume 10, Issue 2
Displaying 1-8 of 8 articles from this issue
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Tadahiro ASADA1982 Volume 10 Issue 2 Pages 51-60
Published: June 30, 1982
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSStudies on deformations and flow mechanisms of polymer liquid crystals are expected to afford us fundamental knowledges to clarify the technologically important phenomena, including fiber formation in liquid crystal spinning. A rheological study alone, however, cannot tell the full story of deformation mechanisms of polymer liquid crystalline systems, because the systems usually form complicated super-structures or textures, the unstability of which have been prevented us from studing the relationship between the physical properties and structures. The author and his coworkers have developed new rheo-optical techniques and investigated the relations between structure and rheological properties of various liquid crystals, including liquid crystalline polymers. In this paper, these techniques and some recent experimental results are introduced.
After a brief introduction to liquid crystals in general and their rheological properties, the rheology of liquid crystalline polymers is summarized by the three-region flow curve. And then rheo-optical properties of these liquid crystalline polymers are introduced. Spectro-photometric method is very effective for studing deformation and flow mechanism of cholesteric liquid crystals. Polarized-light method is expected to be developed for more general use. Both the rheo-optical and rheological properties of a liquid crystalline polymers may be interpreted by supposing three typical structural models for bulk structure of the polymer liquid crystalline system proposed before.View full abstractDownload PDF (1543K) -
Yukuo NANZAI1982 Volume 10 Issue 2 Pages 61-67
Published: June 30, 1982
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSTensile flow of polystyrene and polycabonate in the glass transition region was examined. The behavior at the lower yield point was compared with that at the upper yield point, where the latter is the point of the maximum stress of tensile stress-strain curve right after the elastic limit, and the former is the point of the minimum stress beyond the upper yield point. The upper yield point had been considered as the point where purely plastic flow begins. It was found that the upper yield point was influenced significantly by the glass transition, while the lower yield point was not. The yield behavior at the upper and lower yield points were examined in terms of a phenomenological theory by Brady et al. and molecular theories by Robertson and by Argon for plastic flow of glassy polymers. No satisfactory agreements of the theories with our results for the upper yield point were seen. However, Robertson's structural-temperature theory showed a fairly good agreement with our results obtained at the lower yield point. The results obtained on polystyrene and Polycarbonate coincided qualitatively with those of poly (methyl methacrylate) reported previously.View full abstractDownload PDF (927K) -
Toshiaki KUROIWA, Toru SAKAGUCHI1982 Volume 10 Issue 2 Pages 68-74
Published: June 30, 1982
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSVariation of shearing stress during constant-rate shearing of two thixotropic solutions of polyvinylchloride in dibutylphthalate was measured at various rates of shear with a Weissenberg rheogoniometer. The sample solution was previously sheared at a shear rate j-, until steady-state stress was reached, and subsequently left to stand still for time to before the measurement at a shear rate γ.
It was found that the time-variation of shearing stress generally consists of three successive stages: the first includes a stress overshoot occuring within a few seconds after the onset of flow, the second is a relatively rapid decay of stress which continues for about 100 seconds, and the third is an exponential relaxation of stress which continues until the steady-state at γ is reached.
Shearing stresses of these three stages at fixed γo and γ increased with increasing to over the range of to greater than one month. Steady-state shearing stress for various values of γ0 and to was constant for a given values of γ when γo<γ, while it increased with increasing to when γo>γ.
A rate equation for the structural buildup in the solution for the final stage of stress variation was derived by analysing the experimental data and assuming the proportionality of the viscosity increment to the structural parameter.
The increase of steady-state stress with increasing to was explained in relation to the rate constant in the rate equation.View full abstractDownload PDF (1103K) -
Toshiaki KUROIWA, Toru SAKAGUCHI1982 Volume 10 Issue 2 Pages 75-80
Published: June 30, 1982
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSAccording to the phenomenological theory for thixotropy presented by Cheng and Evans, an equilibrium curve and constant-structure curves can be determined as characteristic shearing stress vs. rate of shear relations for a thixotropic liquid. These curves were obtained by measuring the shearing stress at various rates of shear with a Weissenberg rheogoniometer using two solutions of polyvinylchloride in dibutylphthalate. Solutions of constant structure are non-Newtonian; shearing stress goes to zero as rate of shear approaches zero. Solutions in equilibrium state of structure are suggested to have yield stress. Relaxation spectra of these solutions at various rates of shear were determined from stress relaxation after cessation of steady flow. These results were discussed in relation to the hypothetical formation and destruction of structure in the solution. An empirical equation for the shear-rate dependence of shearing stress of these solutions was derived by analysing the data. This equation is consistent with the Cheng-Evans' constitutive relation for thixotropic liquids.View full abstractDownload PDF (774K) -
Toshiaki KUROIWA, Toru SAKAGUCHI1982 Volume 10 Issue 2 Pages 81-86
Published: June 30, 1982
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSDevelopment of shearing stress after the onset of simple shearing flow of two thixotropic solutions of polyvinylchloride in dibutylphthalate was measured at various rates of shear with a Weissenberg rheogoniometer. The sample solution was sheared at a rate of shear γ0 until steady-state stress was reached, and subsequently left to stand still for a length of time t0. Then rate of shear was changed to a new value γ and transient shearing stress was measured. This procedure was repeated for different combinations of γ0, γ and t0. When γ0<γ, stress overshoot appeared even for vanishingly small t0, and the maximum stress increased with increasing t0 over the range of t0 greater than one month. When γ0>γ. stress overshoot appeared only for t0 greater than a few days. In this case, increase of stress overshoot with t0 was small as compared with the case γ0<γ. These results were discussed from the view point of formation of structure in the solution during to and destruction under shear. Finally, effect of t0 on stress overshoot was compared with the theoretical calculations based on the Bogue model for non-linear viscoelasticityView full abstractDownload PDF (928K) -
Yasufumi OTSUBO, Kaoru UMEYA1982 Volume 10 Issue 2 Pages 87-91
Published: June 30, 1982
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSThe rheological properties of aqueous suspensions of Na-fluor-tetrasilicic mica [NaMg2.5(Si4O10)F2] are studied with a coaxial cylinder rheometer. When immersed in water, a mica particle swells by absorption of water molecules into the interlayer region and subsequently separates into flakes with an aspect ratio of about 1000.
When the shearing direction turns reversely, stress overshoot is observed on the aqueous suspension. This may be attributed to an anisotropic structure caused by orientation of flakes.
The interlayer Na+ ions in Na-fluor-tetrasilicic mica are ion-exchangeable and ion exchange by various cations brings on the marked change in swelling characteristics. Therefore, the rheological properties of the mica suspensions in inorganic electrolyte solutions vary with the degree of swelling.
Microscopic observation of the mica films prepared by drying suspensions shows that the difference of swelling characteristics has a direct effect on the film structure.View full abstractDownload PDF (1280K) -
Shinichi SUTO1982 Volume 10 Issue 2 Pages 92-96
Published: June 30, 1982
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSIn order to discuss effects of branching and shear history on die swell, die swell has been determined for a series of low density polyethylenes characterized in terms of their molecular weights and branching indexes. Several slit dies with different gaps are arranged in series in order to form stepwise converging channels.
Die swell increased with branching. Die swell through the stepwise converging slit die depended almost solely on the final die, and effect of shear history on elasticity was not observed. Die swell of low density polyethylene was governed by Weissenberg number (ratio of principal normal stress difference to shear stress at the wall).View full abstractDownload PDF (529K) -
Ryoichi KATAOKA, Satoshi SUZUKI, Shigeki MITAKU, Akira IKEGAMI1982 Volume 10 Issue 2 Pages 97-100
Published: June 30, 1982
Released on J-STAGE: November 20, 2012
JOURNAL FREE ACCESSWe studied the mechanical properties of the sarcoplasmic reticulum of rabbit skeletal white muscle by measuring the ultrasonic velocity and the absorption per wavelength as functions of temperature and ultrasonic frequency. The bulk modulus of sarcoplasmic reticulum was determined from the ultrasonic velocity to be 3.0×1010 dyn/cm2, and the bulk viscosity calculated from the absorption was 5~6 poise at 37°C. The bulk modulus slightly decreased as the temperature increased. The bulk viscosity showed large decrease below 20°C and small change above 20°C. Arrhenius plot of the bulk viscosity revealed the change in the activation energy: 8 kcal/mol below 20°C and less than 4 kcal/mol above 20°C. Considering the fact that the activation energies of Ca+2-uptake and ATP hydrolysis show changes at about 20°C, we conclude that this result suggests the close relationship between the activities of membrane integral proteins and the viscosity of the membrane. The frequency dependence of the limiting numbers of ultrasonic velocity and absorption at 25°C showed a dispersion and a peak, respectively, showing that there is a relaxation in the sarcoplasmic reticulum membranes at about 25°C.View full abstractDownload PDF (563K)
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