This article is author's personal recollection of his research on dynamics and rheology of polymeric liquids carried through the last forty years. It describes particularly (1) his earlier study on Weissenberg effect of concentrated polymer solutions, (2) solution rheology of styrene (S) and butadiene (B) rubbers including SB-block copolymers in mixed solvent with varying selectivity, and finally (3) very recent work with Adachi at Osaka on dielectric normal mode spectroscopy of dilute blends of probe polyisoprene (PI) in matrix polybutadiene (PB). The major results were (1) the discovery of M-independent compliance of entangled polymer solutions;(2) plastic flow behavior of SB-diblock copolymer solution in a selective solvent decane presumably due to the formation of a crystalline structure of the block copolymer micelles with S cores and B cilia; and (3) the identification of Rouse-like behavior in high M-PI/low M-PB blends and pure reptation behavior (with M3-dependent relaxation time) in low M-PI/high M-PB blends. These results suggest that in the relaxation of monodisperse entangled melt the contour length fluctuation is probably unimportant but rather the relaxation proceeds through pure reptation accelerated by constraint release via tube renewal.
The effect of alkalic salts on the apparent viscosity of soybean protein was investigated using a modified coaxial cylinder viscometer. The apparent viscosity increased with a rise and with a fall in temperature in ascending order of Hofmeister's series. A technique of measuring the dynamic viscoelasticity of human skin in vivo was developed. With it,the mechanical properties of the skin are measured using decade filter and newly developed noise suppression logic. The technique is sensitive enough to detect the difference in visco-elasticity between sites of the body, and the differences before and after application of cosmetics. We developed a new evaluation system for the quantitative analysis of facial wrinkles. This system enables us to obtain precise three-dimensional information based on the curved shape measurement. Using this system, we can quickly classify the wrinkles at the corner of the eye “crow's feet” into coarse or intermediate wrinkles and fine wrinlde. This system was applied for the quantitative analysis of wrinkles in association with aging in 275 skin surface negative replicas of the“crow's feet”site in Japanese females ranging in age from 20 and 80 years. Data clearly revealed that the wrinkles could be extracted from the other three-dimensional data. In addition, it was confirmed that most of the coarse or intermediate wrinkle parameters gradually increased with age, while the fine wrinkle parameters increased up to the middle age and decreased thereafter. These results suggest that the formation of coarse or intermediate wrinkles must be caused by different mechanisms than that of fine wrinkles.
A package of computer programs has been developed for CAE (Computer Aided Engineering) in the injection molding of thermoplastics. It consists of mold cooling, polymer melt flow, fiber orientation, material properties, and stress analysis programs for 3-dimensional thin-walled molded parts. They are integrated by using a common geometric model and are used to predict the quality of molds and molded parts at the stage of design. This article summarizes the theory and verified results of the polymer melt flow, fiber orientation, and material properties analyses associated with rheology.
Fatigue behavior of polymeric solids has been paid great attention these days, since various high performance polymers and polymer composites have been ap-plied for structural components. However, little investigation on polymer fatigue has been made on the basis of dynamic viscoelastic behavior. The purpose of the present study is to analyze the fatigue behavior of polymeric materials on the basis of nonlinear dynamic viscoelastic measurement during the fatigue process and to reveal the fatigue mechanism of polymeric solids. A fatigue tester which enables continuous measurement of dynamic viscoelasticity and the surface temperature under sinusoidal strain has been designed. Fatigue tests have been carried out for various polymeric solids including amorphous glassy polymers, crystalline polymers, oriented polymers, elastomers and polymer composites. It was revealed that the dynamic viscoelastic behavior and surface temperature rise during the fatigue process can be classified into brittle and ductile failures. The amount of energy dissipated for irreversible structural change was calculated from the viscoelastic energy loss and the amount of heat generation. The fatigue criterion on the basis of viscoelastic energy loss dissipated for irreversible structural change has been established for various polymeric solids. The fatigue analysis procedure mentioned above has been successfully applied to glass-fiber reinforced polymer composite. In order to reveal the effect of nonlinear viscoelasticity on the fatigue behavior, a quantitative measurement of nonlinear viscoelasticity has been carried out based on Fourier analysis of response stress. It was revealed that the degree of nonlinear viscoelasticity was closely related to the fatigue strength. Finally, the origin of nonlinear viscoelasticity has been discussed.
We examine the principle of the normal stress measurement with a sliding plate rheometer proposed by Oakley and Giacomin (Polym. Eng. Sci., 34, 580 (1994)). In this rheometer, a sheet of material is held between a pair of plates and a simple shear is applied by the parallel motion of the plates. They state that the pressure of the material on the plate is equal to the first normal stress difference, N1, and the negative second normal stress difference, -N2. This statement is evidently wrong. It is shown here that the pressure at the rim of the sheet can be related to the normal stress differences. The pressure at any point is equal to N1 if the sheet is infinitely long in the neutral direction and it is equal to -N2 if the sheet is long in the shear direction. These conditions can be fulfilled with a coaxial cylinder system if the radius is large and the gap is small. The first normal stress difference in oscillatory shear may be evaluated from the pressure in translational (piston-like) motion of a coaxial cylinder system.
Izod impact strength is examined in respect of its relation to chemical structures. Entanglement density and the characteristic ratio of the mean square end-to-end distance of a actual polymer against to that of an idealized freely joined chain (C∞) are used, as parameters representing the chemical structure of the polymers. A functional relation is found between the Izod impact strength and the ratio of the entanglement to C∞. A method for predicting the Izod impact strength from the chemical structure of the polymer is reported.