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SynopsisTo obtain information on the change in fine structure of nylon 6 taking place during practical false-twisting processes, the manner of change in the three elemental processes, i.e., twisting, annealing, and untwisting, was studied. For simplicity, nylon 6 gut yarn was used instead of multifilament yarn. Wide-and small-angle x-ray diffraction (WAXD and SAXD) together with electron microscopy (EM) were used here. The degree of molecular orientation in the crystalline region of the twisted yarn gradually decreases with increase of the twist number ( T N ) in the region of TN >> iW. The long spacing, determined by SAXD, of the twisted yarn increases with increase in TN.The increase in long spacing cannot be interpreted only by macroscopic strain or elongation of the yarn in the twisting process. This difference seems to arise from the contribution of the decrease of lateral size of lamellae to the average long spacing; therefore the increase in long spacing should be attributed to the elongation of the amorphous region, deduced from the crystallinity measured by WAXD and the long spacing diffraction. The angle between the streak line on the surface of twisted yarn observed by EM and the fiber axis agrees well with the twist angle of the yarn. The crystal lamellae are stacked normal to the streak line a t the initial stage, i.e., a t a low value of TN, but they begin to deviate from the normal direction with increase in TN, accompanied by their partial destruction. Based on SAXD and density measurements, the internal strain of yarn annealed after twisting is fully relaxed. When the yarn is untwisted after twisting and annealing, the crystal orientation recovers gradually to that of the untreated yarn. The chain axis within the lamellae in the center region of the yarn becomes nearly parallel to the fiber axis, but the chain axis in the outer region does not.

Quiescent and strain‐induced crystallization of poly(p‐phenylene terephthalamide) (PPTA) from sulfuric acid solution has been studied. Negative spherulites (SA‐PPTA spherulites) are formed from hot concentrated solutions by cooling. The spherulite consists of radiating fibrous lamellae several hundred angstroms wide. The electron diffraction pattern indicates that PPTA molecules are oriented perpendicular to the long axes of the fibrous lamellae and that the [010] or [110] direction of the modification I crystal and [010] direction of the modification II crystal are parallel to the long axes of the fibrous lamellae. The width of the lamellae is much smaller than the chain length of the starting PPTA. It appears that hydrolysis of PPTA during melting crystallization determines the chain length, i.e., the width of the fibrous lamella. Stacked, lamellar structures like “row structures” are formed under shear. The longer axes of the fibrous lamellae are oriented perpendicular to the shear direction. It is confirmed by electron diffraction studies that the PPTA molecules are oriented parallel to the shear direction. Well‐developed fibrils with the PPTA molecules oriented to the fibril axis, are formed by adding the SA‐PPTA spherulites to water with vigorous stirring.

(1) PHENOMENA OF THE PILLING For the purpose of studies on the pilling tendencies of the textile fabrics, the polyethylene-, terephthalate and viscose fibers blended fabrics are subjected to the constant rubbing action by using the Random Tumble pilling tester.The mean number of pills on the surface of fabric against the rubbing time are evaluated, and pilling tendencies which correlated with them are discussed. Futhermore, the formative process and the grown state of pills are experimentally confirmed by the microscopic examinations.1) If a curve of the mean number of pills against the rubbing time is divided off the several regions according to the changing propensities of the curve, the tendencies from the formation to the wear-off of pills can be perceived.2) By the microscopic examination, the formative process of a pill is accurately seen. It is found that the grown pills consist of a body and leg parts.3) The polyethylene-terephthalate fibers are apt to make more pills as compared with the viscose fibers.4) It is found that some of pill bodies contain a node or the assembly of nodes, that is, they contain so-called "pill nucleus".In this parer, the growth mechanism of pills are especially investigated by the microscopic examination, and the pilling tendencies are discussed in detail.The results obtained are as follows :1) The mechanism of a pill body such as the fullness and the motion on the growing process of pilling are expressed by the model.2) The changes of pill size against the rubbing time are evaluated with the apparent volume of the pill body, and several propensities by changing the volume are discussed.3) Effects of the legs on the growth of a pill body play a more important role in such a growing process.

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