The mechanical properties of polypropylene/polypropylene (PP/PP) composites consisting of homo-polypropylene fiber and propylene-ethylene random copolymer matrix were investigated. Generally, it has been already recognized that a transcrystalline layer is formed at the fiber/crystalline matrix interface. However, it is still uncertain whether this transcrystalline layer affects the mechanical properties of the composite material. Therefore, two types of unidirectional PP/PP composites with different impregnation conditions were fabricated by using a film-stacking and compression-molding method, and the effects of the transcrystalline layer on mechanical properties of PP/PP composites were examined. It is possible to form a much more transcrystalline layer at fiber/matrix interfaces by improving the impregnation conditions. Tensile tests in the 0°, 90° and intermediate loading directions were carried out. In the tensile tests at 0° and 90°, the tensile moduli in both directions increased with improving impregnation conditions, and particularly in the 90° direction, the improvement of tensile modulus was remarkable. On the other hand, in the intermediate loading directions θ=45°∼60°, the tensile moduli of the good impregnation samples were lower than the tensile modulus in the 90° direction. It is believed that these results are related to the structure of the transcrystalline layer. The lamellae in the transcrystalline layer grow perpendicular to the fiber and are able to elongate in the 90° direction. Therefore, in the 90° direction, the lamellae can transfer stress to the reinforcing fiber directly. On the other hand, in the 45° direction, the lamellae are difficult to elongate and transfer of stress to the reinforcing fiber is difficult. In all loading directions, the tensile strengths were slightly increased with improving impregnation conditions.

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The prediction of anisotropy of the thermal expansion coefficient and its distribution in molded products is important to improve the accuracy of numerical simulation for product warpage.
We have previously proposed a prediction method whereby the molecular orientation of each layer of a molded product is found from the shear stress distribution produced by the resin flow velocity distribution during molding. The anisotropy of the thermal expansion coefficient and its distribution in the thickness direction are then predicted from the molecular orientation ratio distribution. When this method was used to examine the molecular orientation ratio and the anisotropy of the thermal expansion coefficient of a non-crystalline material, it was shown that a good correlation exists between the two.
The aim of the present research was to examine a method of predicting the molecular orientation ratio distribution in the thickness direction of a molded product, which is induced by resin flow. Detailed measurements were made of the resin flow velocity in the thickness direction of a molded product during the molding process using a visualization mold and the PIV method. The measured data were used to calculate the shear stress distribution, and a comparison was made with the molecular orientation ratio distribution of the molded product. The results made clear the following points.
(1) The maximum shear stress calculated from the resin flow velocity distribution was the smallest near the surface of the molded product and the shear stress increased toward the center of the product.
(2) The molecular orientation ratio of each layer of the molded product was determined by the impulse produced under the impact of shear stress during the molding process and correlated well with the tendency for shear stress to increase toward the center of the product.
These results indicate that the molecular orientation ratio can be predicted from the distribution of the resin flow velocity and that the thermal expansion coefficient, which shows a good correlation with the molecular orientation ratio, can be predicted from the resin flow velocity distribution.

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The solid bed (SB) break-up (BUP) phenomenon seen in the single-screw plastication system causes instability in the plasticating process, and clarification of the generation mechanism is required. In our previous reports, we proposed two kinds of BUP generation models by a dynamic visualization method using a glass-inserted visual heating cylinder. In this study, visual analyses of the plastication process with the standard screw and long feed screw were carried out, and the influence of screw feed-zone length on BUP phenomenon was clarified. The results are summarized below:
1) The SB structure when BUP occurs was clarified by static visualization in cooling and screw extraction experiments, and the validity of the two BUP generation models was confirmed.
2) The polyamide plastication process of the long feed screw was visualized, and it was clarified that BUP of SB occurs in the long feed zone. BUP was assumed to occur in the feed zone where the SB structure changed from the Tadmor type to the melt invading type.
3) This generation process is considered different from the two BUP generation models proposed so far, and the following new model was presented:
The invading type SB is pushed up to the cylinder wall by the pressure of the invaded melting layer between SB and the screw wall. This increases the shearing force between SB and the cylinder wall to generate a large tension in SB, resulting in BUP of SB.

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Dennis et al examined in detail the influence of the structure of extruder and screw on the nanocomposite formation of polyamide 6/organically modified montmorillonite (5%).
In this paper, the relation between the degree of delamination of clay and the mechanical properties of nanocomposite is quantitatively clarified, by using the above data.
As the delamination proceeds, the mechanical properties (tensile yield strength and tensile modulus) increase. This tendency is like reverse S-type curve. The relation about impact strength cannot be clarified definitely, but its maximum value may exist at the region of insuffrcient delamination.

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