Poly-xylyleneadipamide filaments are produced by melt spining followed by either rapid cooling in quenched air or by gradual cooling in a heated hood.
The cross-sectional distribution of birefringence of undrawn monofilaments produced by there two methods is observed by polarized microscopy. The relationship between birefringence distribution and mechanical properties of the undrawn filament is discussed.
The results are following: 1) When molten filaments are gradually cooled by using a heated hood, their cross sectional distribution of birefringence is more uniform than that when they are rapidly cooled. Namely, the birefringence difference between the surface and the center of the monofilament is little.
2) Tenacity and elongation at break of a undrawn filament having a uniform birefringence distribution are larger than those having a wide distribution.
3) The birefringence distribution of undrawn filaments has an effect upon drawing behavior. Namely, the filament surface which has higher molecular orientation bears the load in drawing, and a filament which has a uniform distribution can be drawn up to a higher draw ratio.

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No method has so far been established for evaluating the yarn knittability before knitting. Thus, any yarn defective in knittability cannot be found out until it is actually knitted. As an aid to solve this problem, we investigated various methods for evaluating the yarn knittability and obtained the following conclusions: (1) The analysis of knitting mechanism revealed that the measurements of eight presumed physical properties of yarns would enable us to evaluate the yarn knittability bebore knitting. (2) So, it is possible not only to find out the defective yarn, but also to clear up its cause. (3) Generally, the following four physical properties have a large bearing on knittability; (a) Unwinding resistance of the yarn out of a cone. (b) Friction between yarns themselves. (c) Friction between the yarn and the knitting needle. (d) Bending moment of the yarn.
Next, we produced an apparatus which made it possible to measure the said four important physical properties, simultaneously and synthetically, in terms of yarn tension. The results of measurements with this apparatus show a good agreement with the actual yarn knittability. Thus, it is found that this apparatus makes it easy to measure the yarn knittability.

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Bi-axial tensile behavior of woven fabrics sewn with open lock stitches was observed by using an Instron type tensile tester with a simple attachment made of a Teflon rod.
Specimens were made into circular cylinders by sewing along warps or wefts. The models mechanically equivalent to these sewn specimens were assumed by the same way as explained in the previous paper[1].
The experimental results were analysed on the assumption that the seam element consists of six straight threads, and when stretched, these yarns are extended with no slip against the fabrics into which the threads are sewn in.
The analysis gives that it is necessary to increase the seam strength by balancing both tensions of the needle thread and the bobbin thread.

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