Recently, the high speed machines appeared in the spinning process and the delivery speed of the drawing machine, for example, reached 400-500m/min. It is considered that the drafting behaviour at high speeds is quite different from that of conventional low speeds. The drafting force tester that is usually used to evaluate the drafting behaviour can not apply at high speed region because the inertia and the vibration of the detecting part become large as the speed increases. In previous paper, it is reported that the lateral deformation of sliver in the roller drafting zone (LD) is one of the important expressions to show the roller drafting behaviour.
In this paper, LD was measured for the delivery speeds of the roller drafting machine and the effects of the delivery speed on LD were discussed. As the delivery speed increases, the mean of LD increases. The coefficient of variation of LD also increases reaching the delivery speed 100m/min. At low delivery speed, LD shows the strong periodicity, but the periodicity decreases rapidly when the delivery speed increases. The wave length of LD is approximately constant irrespective of the delivery speed. The results show the same tendency as the output sliver irregularity for the delivery speeds. It is clear that the drafting behaviour becomes worse, while the periodicity becomes weaker when the delivery speed increases.

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Air permeability is studied for fiber assemblies of low volume fraction between 0.01 and 0.1, In this range of volume fraction, the viscous resistance per unit surface of constituent fibers is known to enhanced, which is attributabre to the fact that for cylindrical fibers, the cross section of pores through which air flows are in open geometry. An approximate formula describing this effect is derived by assuning idealized arrangement of fibers in an equally-spaced lattice. It is compared with the experimental results for the fiber assemblies of wool slivers, of polyester, and of polyester tops to investigate the dependence of air permeability on the fiber properties, the fiber arrangement, and the volume fraction. In addition, the thermal transmittance through the sample fiber assembly and air layer is measured and the influence of air passage is discussed for fiber assemblies of polyester tops.
The conclusions are summarized as follows :
(1) With aid of the derived formula, the air resistance of fiber assemblies can be calculated from the Kozeny's expression in the range of the volume fraction of interest here. The experiments give the results by 4070% smaller than predicted from the theoretical estimate. This is explained by the fact that in actual assemblies, fibers are not in the assumed idealized alignment and made in partial contact with each other.
(2) In evaluating the air resistance, the degree of contact between fibers is an important factor, which is affected by the properties of fibers. Assemblies of wool slivers exhibit the air resistance by a factor of 1.32 larger than those of polyester slivers of same diameter and of the same volume fraction. This is attributable to the crimps of wool which lower the degree of contact between fibers. Assemblies of polyester tops show larger air resistance than those of polyester slivers when the volume fraction is low, which is also explicable as the same effect.
(3) As for the other parameters such as the fiber diameters and the arrangements, the assemblies of low volume fraction studied show the same dependences of air resistance on them as those of large volume fraction.
(4) The effect of air passage on the thermal insulation of fiber assemblies depends on the wind velocity in environment and dominates over the heat transmittance if wind velocity is greater than1 ms^-1.

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The formulas for velocity distribution, tension and running time of viscoelastic yarn, which runs between feed-roller and take-up roller in a steady state, are obtained using one-dimensional constitutive equation of the integral type described in a convected coordinate system. The formulas may be expressed simply by creep compliance of yarn, draw ratio and feed-roller velocity.
Predictions of velocity distribution, tension and running time agree with the experiments of polyethylene terephthalate monofilament yarn. The tension increases with feed-roller velocity and draw ratio. Both calculated and observed curves of velocity distribution along a yarn are convex upward and increase monotonically. However, the observed results are smaller than the calculated ones. Furthermore, the velocity gradient increases with draw ratio in calculations. The observed velocity gradient is larger than the calculated one. Lastly, the running time decreases with draw ratio and this tendency is remarkable at low feed-roller velocities.

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