The fiber orientation in molded plastics is caused by the flow in the manufacturing process. An investigation has been made of the influence of parameters such as fiber length, volume fraction and viscosity of carrier medium on the decree of fiber orientation.
The object of this work is to determine the degree of the orientation of short fibers contained in the polymer solution during the flow through parallel slits. Furthermore, the fiber orientation in converging and diverging flows is investigated. The distributions of fiber orientation at various parts of parallel slits are found to be the normal distribution, whose standard deviation is obtained as a function of shear rate. The convergent flow results in high fiber align ment along streamline. On the other hand, the divergent flow caused some fibers parallel to the streamline and perpendicular to the streamline.

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The change in fine structure of polyethylene terephthalate (PET) yarns textured by the false-twisting process was studied. For simplicity, the monofilament yarn of PET, the diameter of which was about 0.6 mm, was used instead of multifilament yarns in this study. The false-twisting process was divided into two stages, i.e., (i) twisting and heat setting stage and (ii) untwisting stage. The changes in fine structure in each stage were investigated by wide-and small-angle X-ray diffraction methods and the measurements of densities and melting points.
In the twisting and heat setting stages, the degree of orientation of the molecular chain in the crystalline region gradually decreases with increasing the number of twists. It changes steeply especially in the region of more than 200 tpm. The angle between the fibril and the fiber axis agrees well with the twist angle of the filament calculated based on the model. The crystallinity, the crystallite size as well as the structure of long period unit are scarecely affected. While the lattice distortion within the crystallites increases with increasing the number of twists.
In the untwisting stage, the direction of fibrils almost recovers accompanying the recovery of crystal orienation in the twist region of less than 133 tpm. In the region of more than 200 tpm, however, the crystal orientation partially recovers and the value of the orientation factor remains at the lower values than that of th untreated sample. Thechanges of the crystallite size and the structure of long period unit are not appreciable even in this stage. The minute crystallites with large lattice distortion, formed in the twisting and heat setting stages, are destroyed resulting in the slight decrease of crystallinity.

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The change in fine structure of polyethylene terephthalate (PET) yarns textured by the false-twisting process was studied. To simulate a false-twisting textured yarn of multi-filament yarns, the three-filament yarns of PET were used instead of the single monofilament yarns whose behavior wasCdiscussed in the Part 1.
In the twisting and heat setting stages, the degree of orientation of the molecular chain in the crystalline region de creases with increasing the number of twists accompanying the increase in the inclination of a filament itself and fibrils. Especially it was noted that the lamellar crystals were tilted in the region of more than 138 tpm and that the folded plane which is the interface between the crystalline and amorphous regions is normal to the fiber axis. The crystallinity, the crystallite size and the lattice distortion within the crystallites were scarcely changed.
In the untwisting stage, the direction of filaments and fibrils almost recovers accompanying the recovery of crystal orientation. However, the tilt of lamellae within the fibrils is preserved so that the interface becomes inclined away from the plane normal to the fiber axis. The crystal lattice distortion increases with an increase in the number of twists.

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The physical properties of water absorbent porous acrylic fibers relating to wear comfort, i. e., water absorbency, drying, warmth retention, air permeability and frictional property have been compared with those of cotton and other fibers.
An investigation has shown that, comparing with the regular acrylic fibers, modified water absorbant acrylic fibers :
(1) Are easy in water diffusion and drying.
(2) Has a warmth retention intermediate between those of cotton and acrylic fibers.
(3) Are difficult to lose their air permeability even under the wet condition.
(4) Are difficult to stick to the human skin even under the wet condition.
The above unique characteristics of water absorbent acrylic fibers are a remarkable departure from the conventional acrylic fibers as well as from other synthetic fibers. The water absorbent acrylic fibers, therefore, will result in unlimited creation of end uses where water absorbing properties are important for comfort or fiber performance.

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The newly developed water absorbent fibers are hollow fibers based on the polyester polymer. The side face of fibers is covered by a lot of micro voids passing to the hollow. Water is absorbed in the hollow through the microvoids the capillary migration. The fibers are water absor bent equivalent to cotton fibers. They are featured by the quick drying, less change in bending rigidity and compressive characteristics and less stickiness to the human skin under the wet condition. A wearing tests by using shirts and slacks under the high-temperature and humidity atmosphere have shown that the garments of the water aborbent fibers are less sticky and less cool to the human skin. They also quickly recovers their feeling from stickiness and coolness. It is confirmed that the water absorbent polyester fiber shows the higher wear comfort than those of regular polyester or cotton fibers.

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