Osamu Ishizuka
Yamagata University
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by Osamu Ishizuka.
Polymer | 1980
Osamu Ishizuka; Kiyohito Koyama
Abstract The measurement of elongational viscosity has been carried out with an improved elongational rheometer, sensitive to small elongational forces and measuring simultaneously the diameter of elongating samples. Force distribution was evaluated for various conditions. The method of reduced variables, successful in linear viscoelastic properties, can be applied to the temperature dependence of elongational viscosity only at small elongational strain rate. For large elongational strain rates, the elongational viscosity was found to be non-linear and a new method characterizing non-linearity was proposed. The non-linearity parameter in elongational viscosity was independent of elongational strain rate and almost independent of temperature. Non-linearity in elongational viscosity is discussed in terms of a structural change in the polymer melt.
Polymer | 1977
Osamu Ishizuka; Kiyohito Koyama
Abstract The crystallization kinetics of the running filament in melt spinning have been studied for three cases: isothermal crystallization of an isotropic melt, non-isothermal crystallization of an isotropic melt, and non-isothermal crystallization of a non-isotropic melt. Both the temperature and the orientation dependences of nucleation rate and growth rate are estimated for polypropylene. Calculated curves for non-isothermal crystallization of a non-isotropic melt with partial high orientation closely approximate the experimental data. In particular, the experimental data are best explained by crystallization with two-dimensional growth. The crystallization processes in melt spinning may be governed by localized molecular orientation of the supercooled melt in the initial stage.
Polymer | 1980
Osamu Ishizuka; Kiyohito Koyama; Haruo Nokubo
Abstract The elongational viscosity of polypropylene has been investigated by isothermal melt spinning, carried out over a range of experimental conditions. The filament diameter and the elongational force were measured for running filaments and the relationship between elongational viscosity and elongational strain rate reported. The elongational viscosity was observed to decrease in the vicinity of the spinneret and then remained constant before increasing along the thread line. An increase in elongational viscosity did not occur within the isothermal zone until the elongational flow was fully developed. The onset of an increase in elongational viscosity was determined from the constant total elongational strain. The degree of molecular orientation was also studied by birefringence measurements and was investigated as a function of elongational stress. At a high elongational stress, the relation between birefringence and elongational stress departed from linearity and exhibited a rapid increase which can be related to the increase in elongational viscosity.
Journal of Polymer Science Part A | 1978
Masatomo Minagawa; Masao Okamoto; Osamu Ishizuka
Sen-i Gakkaishi | 1976
Osamu Ishizuka; Kiyohito Koyama
Sen-i Gakkaishi | 1982
Kiyohito Koyama; Osamu Ishizuka
Sen-i Gakkaishi | 1976
Osamu Ishizuka; Kiyohito Koyama
Sen-i Gakkaishi | 1988
Kiyohito Koyama; Katsuhiro Aoki; Osamu Ishizuka
Sen-i Gakkaishi | 1980
Kiyohito Koyama; Osamu Ishizuka
Polymer Journal | 1980
Kiyohito Koyama; Osamu Ishizuka