Improvement of surface transferability of an injection-molded polymer was examined by using heat insulating layer-coated molds. Polyimide (PI) and HIPS were used as the heat insulating material and molding polymer, respectively. Although the transferability of the mirror-finished mold surface, i. e. gloss of the molded surface, depends both on the thickness of PI layer and on the molding conditions, e. g. injection velocity and temperature of polymer, the PI layer of about 0.1mm thickness enables us to obtain sufficient transferability with negligible elongation of the cycle-time.
In order to examine the relation between the thickness of thermal insulation layer and the improvement of surface transferability due to the PI layer, time-dependent temperature distribution near the mold-polymer boundary was numerically studied. The results showed that the temperature of PI layer coated on the mold surface rises immediately after the layer is in contact with the polymer melt, and that the period during which the mold surface temperature is kept at high increases with increasing the PI layer thickness. We therefore concluded that the molding pressure applied during the period is effective for improving the surface transferability of the molded.
From the practical viewpoint, the PI layer covered with nickel surface layer was also tested, and the improvement of surface transferability was correlated with the integration value ΔH of the excess temperature of the mold surface over the glass-transition temperature of polymer to the time elapsed. The result clearly showed that the significant improvement of surface transferability can be obtained only under the condition where the ΔH value is higher than 2s·°C.

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The crystallinity of polymer films is very important factor for research as well as manufacture. Several techniques such as X-ray diffraction, density and DSC are used for measuring it. But these methods need much time and labor. A new method for measuring the crystallinity of PET films more easily and quickly by using complex dielectric constants measured by a microwave cavity resonator at 4 GHz has been developed. We obtained good correlation between the density method and the new method by complex dielectric constants for biaxially stretched PET films as well as unstretched PET films.

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A three-dimensional flow visualization of a polyacrylamide/corn-syrup aqueous solution was carried out, using a 2.5:1 abrupt contraction with 3:1 aspect ratio. A numerical simulation of three-dimensional flow was also carried out with an Oldroyd-B model in the same geometry. The numerical results were compared with the visualization results.
The experiment shows that a lip vortex takes place near the front wall at a low flow rate, but is not observed near the central part of the lip corner at the same flow condition. The lip vortex then develops with increasing flow rate into a larger corner vortex. Under the experimental conditions of the present paper, the lip vortex has an important influence on the development of vortex enhancement in the 3-D abrupt contraction. For some combinations of rheological parameters, the numerical results agreed qualitatively with the experimental results.

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Measurement of fiber orientation is an important inspection item to examine the shape and strength of products. Fiber orientation has been measured from photographs of thinly sliced FRP or by observation of the orientational behavior of maker fibers. However, only two dimensional fiber orientation is obtained with photographs. In recent years, the measurement of three-dimensional fiber orientation using scanning electric microscopy has been reported. However, research data on three-dimensional orientation distributions is insufficient. We report on a method of measuring the three-dimensional fiber orientation using the scanning acoustic microscope.
The method to we propose involves visualizing the interference fringes along the fibers, and calculating three-dimensional fiber orientation of parameters from these interference fringes. Finally, the distribution of fiber orientations is measured at each position. A merit of the method that we propose is the lack of ambiguity in comparison with a method using elliptical marks on sectioned polished surfaces and this method is not influenced by noise patterns.
The following results were obtained:
(1) We were able to measure the three-dimensional fiber orientation non-destructively.
(2) Using a test pattern, the measured orientation parameters almost agree with the theoretical parameters.
(3) For test specimens with uneven surface, we confirmed the vertical distribution of the fiber orientation in the concave position of the surface.
We were thus able to confirm the validity of the proposed method by experiments.

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Sheath-core type bicomponent fibers consisting of poly (ethylene terephthalate) (PET) as a sheath component and thermotropic liquid crystalline polymer (LCP) as a core component were prepared by a high-speed melt spinning process, and continuous fiber-reinforced thermoplastic composites were fabricated from these fibers. The processability of LCP was improved by co-processing with PET, and tensile modulus and strength of the LCP component in the PET/LCP bicomponent fibers were enhanced in comparison with LCP single component spinning. Wide-angle X-ray diffraction patterns showed that the molecular orientation of LCP component in thermoplastic composites did not change as compared to those in the as-spun bicomponent fibers. The tensile modulus and strength of PET/LCP bicomponent fibers and thermoplastic composites were also similar. To combine the fiber spinning process with the thermoplastic composites processing, thermoplastic composites with a structural gradient in fiber content were also fabricated from the bicomponent fibers in which sheath-core composition was continuously changed during the spinning process. In the three-point bending test of these composites, different mechanical behavior, depending on load direction, appeared. This behavior of the composites prepared in our study is similar to that of bamboo which has a very similar structure.

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[in Japanese]

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