In this paper the correspondence of the induced pressure in twisted sliver with the compressed paessure in loaded wad was measured under such equilibrium condition that both of frictional forces at the two ends of metal wire inserted partly in the wool wad and partly in the twisted wool sliver were balanced (see fig. 1). At the balanced frictional state (see fig. 2), the experimental relations between the twist angle θ (deg/cm) of sliver having fullness (1-ε)_s and the applied load R (g/cm²) of wad having fullness (1-ε)_w are shown in fig. 4. On the other hand, the effect of R on the withdrawal force F_w (g/cm) of single fibre from this wad was described by inverse sigmosoidal curve in fig. 5, and the dependence of F_w on R/(1-ε)_w was obtained linearly as shown in fig. 7. Thus, frictional coefficient of wool fibre was estimated to μ₀=0.26 by Postle-Ingham's method²³⁾. And then, the dependence of average frictional force F_t (g/cm) of a fibre in wool sliver on its twist number n (cm^-1) was estimated from the load-elongation curves of twisted wool sliver. In fig. 10, this relation of F_t and n was plotted exponentially.
From these experimental results, detailed assignments of the mechanical state of a fibre in twisted sliver have been made as follows:
(1) In fig. 12 it is shown that the value of radial pressure P_w (g/cm) produced on the unit length of axial centre line of twisted sliver increases quadratically as twist number n increases.
(2) Inter-fibre frictional force F_t of twisted sliver increases with two sets of factors: one is bulk density increment of sliver by twisting, and another the curvature increment of fibre arrangement. The observed values of the former efiects on the frictional force of single fibre are given as F_w/4 in fig. 10, and those of the latter effect as (F_t-(F_w/4)) in fig. 10.
(3) The tortional behavior of wool sliver as a whole is similar to the spongy material, for the orientation of fibre in a twisted sliver was not arranged to regular spiral configuration, but intercected mutually as the results of fibre migrations. This makes possible to suggest that the value of inter-fiber frictional cofficient μ in twisted sliver is larger than that of μ₀ in untwisted wool wad. Actually, inserting the observed values of F_t/(F_w/4), the average ratio of frictional force along the generating line of unit length, into eqs. (6), (7), calculated value of μ was about 1.

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Dynamic viscoelastic properties in relatively low amplitude (0.30% elongation) and low frequency (1.21 c. p. s.) have been measured for several tire cord samples prepared under various spinning conditions and also various twisting conditions. The results are discussed in connection with the internal structures of the individual filaments and also with the cord structures. The following. observations are made:
1) The frictional properties of the filaments are varied by changing the oiling treatment. However it was found that the frictional properties has very minor effects on the overall viscoelastic properties measured under these conditions.
2) The cord structure was controlled by changing the number of twists and also the procedure of twisting. Apparently the properties of tire cords are governed exclusively by the cord structures.
3) The internal structure of filaments, determined by the combinations of factors such as crystallinity, size of crystallite, degree of orientation, contribute strongly to the cord structure. Thus, even the same number of twists and the identical proceedure of twisting were applied, the cord structures were markedly different depending upon the properties of individual filaments used. As the results, it was found difficult to isolate the direct effects of internal structures of individual filaments on the final viscoelastic properties of cords, because of the strong interposition of the effects of cord structures on the properties in the low amplitude.

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Crystallinity of polypropylene fibers subjected to dry- and wet-heat-treatment under tensionless and fixed states, was examined by x-ray diffraction by the following procedures:
The degree of crystallinity was determined by measuring the intensity areas of the crystalline and amorphous portion derived from the X-ray diffraction intensity curve on the powdered specimens. At this point, the diffraction intensity correction was made for counting loss and polarization Lorentz's factor. The crystallite dimension (crystal width) was determind with the half-width values obtained from the diffraction intensity curves of the (110) and (130) planes in equatorial scan on the fiber specimens. The orientation of crystallites was determined from the half-width values of the diffraction intensity curves along the Debye-Scherrer ring in the (110) and (040) planes. (In this study, the unit cell dimensions of polypropylene were based on Natta's data, as follows; a=6.65, b=20.96, c=6.50Å, β=99°20′, SG C⁶_2h-C2/c.)
The degree of crystallinity and the crystallite dimension increase by heat-treatment, more conspicuous by wet-heat-treatment. These changes in crystallinity become more remarkable in the heat-treatment above 120°C. The degree of orientation decreases by heat-treatment under tensionless state, and increases slightly by heat-treatment under fixed state. These changes are shown conspicuously in wet-heat-treatment.
From an observation of the relation between the degree of crystallinity and the crystallite dimension, the mechanism of crystallization in heat-treatment is tentatively discussed.

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