In order to establish the various methods for measuring and evaluating the glass transition points of liquid crystalline polymers, a differential scanning calorimeter, thermomechanical analysis equipment and dynamic viscoelasticity measuring equipment were used to measure sample polymers for their glass transition points, thereby identifying any problems involved in the measurements. The measurement using a differential scanning calorimeter was found to be affected by the heat history of the polymer samples measured and their temperature raising/lowering rates, showing that it should be made using samples subjected to little heat by raising or lowering its temperature at a relatively high rate. In the measurement using thermomechanical analysis equipment, a sample polymer was heated continuously from room temperature to 200°C at a constant rate to measure its linear thermal expansion coefficient, which showed a change at its glass transition point. In this measurement, it is necessary to note that the sample is subject to melting and rapid cooling, has a directional property in its linear expansion coefficient and is subject to annealing, resulting in post-shrinkage. In addition, dynamic viscoelasticity measuring equipment was used to measure a sample polymer for its storage elasticity, loss elasticity and loss tangent, thereby evaluating its glass transition point. This measurement, which restricts the sample shape, requires the use of a sample subjected to a heating process to prepare it into a shape suitable for the measurement, causing its glass transition point to become higher with its elastic modulus affected by frequency and temperature to a considerably large extent. This suggested that it is important to make this measurement under properly set conditions.

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This paper is concerned with the optimization of runner design using an injection-molding flow simulation and a mathematical programming method. A rectangular flat cavity with two gates was considered with a design objective to control the position of the weld-line in the cavity by adjusting the diameter of runners.
The optimal diameter of the runners was inversely determined so that the weld-line will appear at a target position on the mold. The optimal solution was obtained by iterating the injection-molding flow simulation and an optimization procedure.
Since the position of weld-line estimated by the injection-molding flow simulator was a discrete value, and the objective function for the problem became a step-like function, it was shown that the conventional optimization procedure might fail to obtain the optimal result for some initial values. An improved optimization algorithm was therefore proposed to obtain optimal solutions for any initial values.

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A liquid isothermal bath (LIB) was introduced into the high-speed melt spinning process of poly (vinylidene fluoride) (PVDF) to modify the temperature and stress profiles in the spinning line. The LIB was placed at 100 or 150cm below the spinneret and the liquid temperature was controlled to 40, 70, 100 and 130°C. The structure of as-spun fibers was characterized by the wide-angle X-ray diffraction, birefringence and Lorentz density measurements. The high-speed spun fibers obtained at the take-up velocities of above 1.5km/min using the LIB showed the mixture of α and β modification crystals, whereas the fibers obtained without the LIB (standard fibers) showed only the α modification crystals. This result indicates that the β modification crystals can be formed directly from the melt in the modified melt spinning process. The weight fraction of β modification crystals showed a minimum with an increase in the liquid temperature suggesting that the mechanism of the formation of β modification crystals in the low and high temperature regions are different. The birefringence and Lorentz density of the as-spun fibers increased with an increase in the take-up velocity and the fibers obtained at high speeds with high liquid temperatures showed higher birefringence and Lorentz density than the standard fibers obtained at the same take-up velocities. The weight fraction of β modification crystals and birefringence were higher for the fibers produced using the LIB with increased liquid depth. The mechanism of fiber structure formation in the spinning process modified with the LIB was discussed based on the enhanced elongational stress and controlled filament temperature, which originated from the high friction force and high heat transfer coefficient at the interface between the liquid and the running filament.

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[in Japanese]

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