Rheological properties of particle suspensions, in which particulate coagulation structures are involved, have been described briefly. Magnetic Ba ferrite and/or smectite were selected as the dispersed particles. The flocs composed of both magnetic particle aggregation and immobilized medium components play an important role of suspension fluidity in such a manner that they make kinds of chains. High concentration of magnetic particles in the system results in the networks among these flocs or chains in a medium. In aqueous suspensions containing smectite particles which form "card house" structures by electrostatic interaction, different types of the networks among those clay particles exist in the dispersion system. Complicated rheological characteristics of the suspensions could be explained by the dynamical mode change in the networked coaguration structures.
Various polymer materials have been developed in accordance with requirements for high functional and high performance products in recent years. These polymer materials become useful end products through polymer processing. Linear viscoelastic rheology and non-linear rheology are dominant factors for good polymer processing. Non-linear rheology is mainly studied on several polymer melt systems by newly developed rheometers and new characterization methods in the present study. The newly developed rheometers are applied to the flow induced crystallization study and flow induced structural formation experiments in elongational flow as well as shear flow. The control methods of the non-linear rheology are proposed by molecular structure design, meso-structure design, and external field control. The degree of non-linearity, or the degree of strain hardening, of elongational viscosity can be controlled by a small amount of high molecular weight polymer, by an introduction of long chain branching, and by an addition of small particles or small solid fibers. Rheology control methods are applied to the processability of polymer processing such as high speed fiber spinning, foam processing of PP, poly(L-lactic acid) and rice, and blow molding. The new polymer processing CAE system is developed by the use of flow induced crystallization and non-linear rheology of elongational viscosity.
A novel method for multi-body molecular simulations for entangled polymers including branch polymers, polymer blends and copolymers is developed in this study. Entangled polymer dynamics is important in industry and still challengeable in polymer science due to complicated rheology caused by a broad variety of controllable polymer architectures such as molecular weight, molecular weight distribution, long chain branching, copolymerization, etc. and freedom of their blends. Conventional molecular simulations are inadequate to the polymer dynamics in long time range because of huge calculation cost. Theoretical approaches based on reptation theories are essentially difficult for multi-component situations due to the self-consistent treatment of entanglement among many chains. In this study a new method of molecular simulations for entangled polymer dynamics is developed based on the primitive chain network model where polymers are considered as primitive chains forming real network in 3D space similarly to the conventional molecular simulations and distinguishably from other entanglement based models. Reasonable consistency on established scaling behaviors for static and dynamic properties and quantitative agreement with experiments for linear and nonlinear rheology have been confirmed for linear and branched polymers. For copolymers and blends reasonable results have been obtained on phase behaviors.
This paper includes three topics of the unsteady flow analysis of viscoelastic fluids with both numerical and experimental methods, i.e. startup flows in channels, three-dimensional flows, and viscous fingering in Hele-Shaw cells. The first topic presents results of the numerical analysis of startup flows using the Leonov model and results of velocity measurements with laser Doppler velocimetry in abrupt contraction flows. The mechanism of transient change in velocity field was discussed in view of the relation to the stress field. In the second topic, the flow of polymer solutions in a rectangular channel with a cavity is considered. Results of flow visualization and the numerical simulation using the Phan-Thien Tanner model are shown. The relation between a three-dimensional flow in the cavity and elastic properties of viscoelastic fluids was found. Finally, in the third part, the unstable growth phenomenon of the interface between two fluids, viscous fingering, is treated. Some examples of anomalous behavior of fingers in surfactant solutions are presented.
The earth consists of crust, mantle and core. The crust is the earth's surface component, upon which we live. Situated below the crust, the mantle is the dominant component consisting of the earth, making up 80 %. The rheology of the mantle is the key to understanding the working of our mother planet. Peridotite, which is derived from the uppermost mantle, preserves structures and textures that contain information on flow stress and strain (e.g., foliation, lineation and grain size), while the crystal-preferred orientations of minerals (i.e., fabric) reveal the nature of kinematic movement within the mantle. The mantle section of the Oman ophiolite is the largest section of oceanic lithosphere exposed at the earth surface. Extensive structural mapping of these rocks has been conducted throughout the Oman mountain range to unravel mantle processes associated with the generation of oceanic lithosphere. Research in this area demonstrated that the formation of oceanic mantle lithosphere at a fast-spreading ridge involves active mantle flow associated with a mantle diapir.
In production of printed circuit boards, the solder pastes are deposited on the boards by screen printing and the conductive lines are formed by melting the solder particles at high temperatures. For formation of precise patterns and sufficient adhesion, the solder pastes are required to hold their shapes until the solder particles begin to melt. An evaluation method of practical processability of solder pastes is examined through dynamic viscoelastic measurements in heating process. However, the difficulties arise in cleaning the sensors (parallel-plate geometry in the present study) because the sensor surfaces are covered with the solidified solder after the measurements. By the use of disposable aluminum sensors, the measuring procedure is established at temperatures above the melting points of solder. The temperature dependence of dynamic viscoelasticity would be useful to design the binder resins and to control of reflow processes.