Capillary flow experiments were performed to evaluate the slip property of injection moldable ceramic compounds of Al₂O₃, and the following results were obtained. Firstly, slip velocity u_s was obtained by applying the Mooney method, and the effects of material temperature, particle size and binder composition on the slip velocity were evaluated. Secondly, it was found that the slip velocity changed significantly, when counter pressure was applied at the exit of the capillary. Then, the slip velocity was expressed by an empirical equation considering the pressure effect. Thirdly, an accurate viscosity equation was obtained, based on the pressure dependent slip behavior. Lastly, the flow behavior in a capillary was discussed in consideration of the slip behavior, and the application of counter pressure was found to be effective for realizing high strain rate flow.

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Generation of molding defects in ceramic injection molding, e. g. melt front asperity or surface roughness of an injected part, has been examined by using radial flow in a circular mold cavity. The following results were obtained. Firstly, it was found that an injected part is separated into 2 regions: region I with rough surface and region II with smooth and fine surface. The rough surface of region I results from a rough melt front, which moves to the mold surface and forms the surface of an injected part in the early filling stage. Secondly, front asperity is generated by the blowout of voids at the front surface, which are mixed into the material and by jetting flow. Voids in the sprue can be prevented by applying counter pressure. An injection molding method using a film gate with proper gap and a side gate is proposed. In this method, high pressure is applied to the filling material in the sprue to reduce voids, and it becomes possible to mold parts with smooth surfaces by removing voids in the sprue and jetting flow in the mold cavity.

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Numerical simulations were carried out on a polyethylene/N₂ physical foaming process where homogeneous and heterogeneous nucleations occurred simultaneously, using Shafi's nucleation and bubble growth models to observe the effect of nucleating agent and processing conditions on the size and the number density of bubbles. The interaction between homogeneously-nucleated and heterogeneously-nucleated bubbles could be observed when the pressure was gradually released.

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In order to measure the melt temperature profiles inside the nozzle of an injection molding machine, we proposed a new integrated thermocouple ceramic sensor plated on a zirconia ceramic sheet. In this study, we discussed the relationship between the radial melt temperature profiles inside the nozzle and plastication conditions, and the effects of polymer type and viscosity. The results can be summarized as below:
(1) We confirmed that this sensor can be repeatedly utilized for the exact measurement of melt temperature profiles under actual plastication conditions, high injection rates, and high temperatures.
(2) During the continuous plastication process, the melt temperature profiles and plastication capacity are considerably influenced by the screw position, which is the gap between the screw head and reservoir wall, and by the revolution rate.
(3) The followings were confirmed during the reciprocating plastication process; the temperature drop with an increase in revolution rate, the rise of the average temperature and peak value near the nozzle wall with an increase in the injection rate, and the temperature drop with a reduction of residence time inside the heating cylinder with an increase in the charge stroke.
(4) It was also clarified that the melt temperature of crystalline polymers decreases more than that of amorphous polymers because of the heat of fusion, and that the melt temperature of high viscosity polymers rises and becomes uniform with an increase in the residence time inside the cylinder due to the decrease of the plastication capacity and the increase of heat generation during the shearing process.
(5) Three layers are formed due to the difference in the flow velocity of polymers in the radial direction inside the reservior, and the above effects of plastication conditions are mainly reflected in the middle layer, which has a high velocity.

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In this paper, a correlation analysis between the melt temperature variation inside the nozzle measured using an integrated thermocouple ceramic sensor and the observations of the plastication state using a visual-heating cylinder was carried out, and improvements in the melt temperature variation using a barrier flight screw were studied. The results can be summarized as below:
(1) The temperature deviation profile inside the nozzle showed a maximum around 2.4mm from the nozzle center during the continuous plastication process and around 1.8mm from the center during the reciprocating plastication process.
(2) From the results of the correlation analysis between the melt temperature at the nozzle and observations using the visual-heating cylinder, we confirmed that the melt temperature variation is directly influenced by the plastication state inside the heating cylinder, especially the solid-bed break-up phenomenon.
(3) We confirmed the decrease of the solid-bed after the sub-flight of the barrier flight screw and the considerable effects that this decrease had on the uniformity of the melt temperature.
From the results above, the validity of the melt temperature variation inside the nozzle as a monitor for the synthetic measurement of the plastication state or as a screw evaluation system was proved by the combination of this sensor and the visual-heating cylinder.

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SMC composites, which consist of chopped strand glass mat and resin layers, have been used for structural parts such as transportation vehicles, water tanks, bathtubs and many other applications. When considering the final SMC composite product, the deformation and flow behavior in the molding should be investigated in detail. The main problem is the slippage between inter- and/or intra-layers. Generally, it occurs in laminated materials. Therefore, in this study, finite element analysis was performed to understand the fundamental behavior of the slippage flow in the molding of the SMC. In the FEM analysis, three-dimensional solid elements with a non-linear incremental deformation were employed. A critical shear strain criterion was also employed at the initiation of the slippage. It is the specific value of the shear strain difference at upper and lower of the element to describe the slippage flows between layers.
Fresh inner layer contacts the die surface after slippage flow occurs, technically, this results in a good surface appearance which is the most important characteristics for SMC moldings. The reason is that the non-cure inner layer appears the surface of moldings. Effective usage of slippage deformation/flow can create new high quality SMC products. Thus concept was valified by both experimental and numerical results.

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We have been developed a three-dimensional non-Newtonian and non-isothermal flow simulation code of Twin Screw Extruder (TSE) using the finite element method. This code can simulate the fully filled part with several types of screw elements such as full flight screws, kneading blocks, rotors and their combinations. A marker particle tracking analysis has also been developed to estimate the stress, strain and temperature histories that polymer melts experience in the TSE. These results are expected to be useful data for understanding distributive, dispersive mixing and chemical reactions.
In this paper, simulations for the kneading blocks in a co-rotating TSE are carried out at rotational speeds of 200 and 400rpm. The screw configuration is 2-lobe kneading block with 90° stagger and the number of discs is 10. The pressure and temperature distributions obtained by numerical simulations are verified by experimental observations. A marker particle tracking analysis is also carried out under the same operational conditions. A broader residence time distribution and a higher temperature history are obtained at high rotational speeds. We also discuss the effect of differences in the rotational speed of the TSE on the distributive mixing.

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Fiber orientation of dilute and concentrated suspensions in elongational flow was simulated by using a particle simulation method (PSM). In this method, a fiber is modeled with an array of spheres and the motion of hydrodynamically interacting fibers is followed by solving the translational and rotational equations of motion for each constituent sphere. Computer simulation was performed to predict the microstructure and the rheological properties of rigid fiber suspensions of aspect ratios 5 and 10 at various concentrations (0.1∼22.5 vol%). The computer simulations demonstrate that fibers scarcely interact with each other even in the concentrated regime and their motion follows the classical theory, which is based on the dilute regime.

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Measurements of uniaxial, biaxial, and planar elongational viscosity and step stress relaxation of a low density polyethylene (LDPE) melt were carried out. The description of experimental uniaxial, biaxial, and planar elongational viscosities results by the Kaye-Bernstein-Kearsley-Zapas (K-BKZ) constitutive equation was examined. Three types of damping function forms, Wagner-Demarmels (WD) model, Papanastasiou-Scriven-Macosko (PSM) model, and Luo-Tanner (LT) model, have been proposed in the K-BKZ constitutive equation. These three damping function forms were examined to see which was able to describe the experimental shear, biaxial, and planar damping functions. The experimental shear and biaxial damping functions were described by the LT and PSM models better than the WD model, however, the experimental planar damping function was not described well by any of the three models. After estimating the best parameters in each model by fitting the three experimental damping functions, the uniaxial, biaxial, and planar elongational viscosity was calculated by the estimated parameters. The uniaxial elongational viscosity was predicted best by the LT model, then by the WD, and PSM models. For biaxial and planar elongational viscosity, none of the three models predicted well, thus the lack of suitability of the biaxial and planar elongational viscosity to the K-BKZ model was suggested.

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We have developed a full nonlinear regression program to determine the relaxation spectrum and the nonlinear parameters for differential and integral viscoelastic models that will give the best fit to experimental rheological data. The least-squares procedure is based on the Levenberg-Marquardt method. The program for determining the optimum relaxation spectrum from dynamic linear viscoelastic data includes a function to automatically reset the initial guesses in the computation. The program was tested against experimental data for several polymer melts and a good fit was obtained. This new program was confirmed not only to be reliable but also to reduce the labor of manually resetting the initial guesses. The program for determining the nonlinear parameters was developed for the Phan Thien-Tanner (PTT), Larson, Giesekus and K-BKZ models and the determination from the experimental data of simple shear flow (shear viscosity and first normal stress difference) was performed for several polymer melts. The best-fit curves for all models were in good agreement with the experimental data within the range of experimental shear rate.

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A nonlinear regression program to determine the material constants for differential and integral viscoelastic models was applied to the determination of nonlinear model parameters from both shear and elongational flow data. The availability of this program and reliability of the viscoelastic models were also discussed. The viscoelastic models employed were the Phan Thien-Tanner (PTT), Larson and K-BKZ models with damping functions of the PSM and Wagner types. The determination of the nonlinear parameters for several polymer melts with extension-thinning uni-axial elongational viscosity was successful and all models could predict the steady shear and elongational flow data well. For a low density polyethylene (LDPE) melt with extension-thickening uni-axial elongational viscosity, the K-BKZ model with a PSM damping function succeeded if we used multiple nonlinear parameters and enough number of relaxation modes in the optimization. On the other hand, the program could not determine physically realistic values of the parameters for the other models even if multiple nonlinear parameters were used. The failure of optimization by the program was due to the strong dependence on initial guesses. We confirmed by manual trial and error fitting that the PTT and the K-BKZ with Wagner damping function models could predict both the shear and elongational flow data if we successfully determined the relaxation spectrum. However, the Larson model could not predict both shear and elongational flow data.

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