We observated mechanical character of Commercial Polycaproamide for elongation of the outest laver, which is twisted at constant length. The results are as the following.:
1. The breaking twist (i.e. elongation of outest layer of twisted filament) does not increase linearly with log (rate of extension, ) but shows its maximum when the range of the rate of extension is increased several hundred folds. The observed maximum values are 0.008% extension per second at 60°C, 0.175 at 100°C, 0.2% at 120°C.
2. At the usual load-elongation curve of the same samples, there exist also maximum of elongation in the above range of extension.
The value are 7.9% at 60°C 13.8% at 100°C.
These maximum values may be the resultant the relaxation time of the recrystallisation of microcrystalls, followed by tearing rupture by twists.
3. Notwithstanding different values of the breaking elongation of twisted filaments, their calculated elongation of outest layer shows the same value independent of the number of their twist.

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For textile materials, tensile properties have remarkable time effect due to their visco-elasticity. There are several methods for measuring or evaluating them, but the results are largely depend on the methods used and conditions under which the test is conducted. In this paper, the general methods of measurement and evaluation of textile materials under cyclic deformation at low frequency and large deformation (7.44%) are described. Since the ordinary visco-elastic laws can not be applied to such large deformation, only qualitative evaluation on real textile materials is possible under those conditions.

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The stress in twisted fiber relaxes as elongated, so the twisting moment changes with time under the condition of constant twist. The torsional relaxation in macroscopic meanings is measured and studied with the specimen of raw silk. The twisting moment M decreases with elapsed time t from the initial moment at constant twist T (relaxation in narrow sense) and increases showing a negative value after removing the twist (recovery), an inverse moment remaining permanently. The momentrelaxation in fiber is represented in the following types of empirical formula; M=A-Blogt or M=At^-c, c being almost constant below a certain twist. A and B are the functions of T and so M=ae^αT-bT^β logt for example (500_??_T_??_3000), where a, b, a and β are constant. a=4.65, b=0.0281; α=3.69×10^-4, β=0.415 and c=7.44×10^-2 for relaxation of raw silk (M in mg•cm, T in m^-1, t in min.) The relative moment-relaxation is shown in the similar type of formula as above; M/M₁=1-b′logt or M/M₁=t^-c, where b′ is scarcely dependent on the twist (constant in T_??_2000). (M₁=A i.e. moment of 1 min after twisting or untwisting). As mean value b′=0.0663 for relaxation, 0.168 for recovery. The relations among M, T and t are illustrated in the isochronal curves and the surface of moment-relaxation.

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On the cotton flat card, the relation between the thickness variations in fed laps and produced slivers has been experimentally studied in the following manners: (1) The method of uniform feeding by laying one handred carded slivers in parallel with the whole width of the card and feeding them into the feed roller. (2) By feeding laps with variation in thickness as shown in Fig. 1, caused by adding proper length and numbers of carded slivers on the former uniform feeding.
After the measurements of thickness variations in the produced slivers on these cases, it may be concluded that the carding engine with adequate settings does not cause any variation in thickness of produced slivers, and the thickness variation of ingoing lap is precisely drafted and it appears on the sliver after a certain time (about 35 seconds in this measurement), as the ingoing fibers need this time interval to pass through the carding engine.

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Deterioration and yellowing of silk fibroin were hitherto controlled by methylation with diazomethane, but in this paper it is shown that the shrinkages of silk by neutral salts and mineral acid solutions may be remarkably diminished. The causes of the shrinkage control of silk by methylation with diazomethane are also discussed on the bases of our experiments and many data attributing to the methylation of phenolic hydroxyl groups of tyrosine residues are proposed. Tyrosine residues of silk fibroin are, it is concluded, responsible for the shrinkage phenomena of silk by salts and acids; this conclusion coincides with the preceding study by R. Murase.

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