Raw material & Processing zone upto Yarn stage

Facts behind Yarn Hairiness

GMT 18:15 2016 Monday ,30 May

Sriyadithatextile - Facts behind Yarn Hairiness

Mr. Suresh Kanna - FM at M/s. Jay Textiles, Pollachi

Yarn hairiness is a complex concept, which generally cannot be completely defined by a single figure.The facts behind Yarn Hairiness is well explained by Mr. Suresh Kanna - FM at Jay Textiles, Pollachi - in this exclusive interview.

FACTS BEHIND YARN HAIRINESS: Hairiness occurs because some fibre ends protrude from the yarn body, some looped fibres arch out from the yarn core and some wild fibres in the yarn.
• Pillay proved that there is a high correlation between the number of protruding ends and the number of          fibres in the yarn cross-section.
• Torsion rigidity of the fibres is the most important single property affecting yarn hairiness. Other factors are    flexural rigidity, fibre length and fibre fineness.
• Mixing different length cottons-No substantial gain in hairiness. Although the hairiness of a yarn could be        reduced to some extent by the addition of a longer and finer cotton to the blend. The extent of reduction is    not proportional to the percentage of the longer and finer component. This is probably due to the                  preferential migration of the coarser and shorter component, which has longer protruding ends, from the        yarn body. The addition of wastes to the mixing increases the yarn hairiness; the effect of adding comber     waste is greater than that of adding soft waste.
• Blending-not a solution to hairiness. The blended yarns are rather more hairy than expected from the            hairiness of the components; a result similar to that found in cotton blends. This may be due to the                preferential migration of the shorter cotton fibers; a count of the number of protruding ends of both types      of fiber shows that there is more cotton fiber ends than expected, although the difference is not very great.
• The number of protruding ends is independent of twist, whereas the number of loops decreases when the        yarn twist increases because of a greater degreee of binding between hte fibres owing to twist.The number    of wild fibres decreases only very slightly with twist because of their position on the yarn periphery.
• The proportion of fiber ends that protrude from the yarn surface, counted microscopically has been found to    be about 31% of the actual number of ends present in the yarn.
• If the length of the protruding fibre ends as well as that of the loops is considered, the mean value of the        hairiness increases as the cross-sectional area increases and decreases with the length of the loops. The        hairiness is affected by the yarn twist, since an increase in twist tends to shorten the fibre ends.
• Wild fibres are those for which hte head alone is taken by the twist while the tail is still gripped by the front    drafting rollers.
• Fibre length influences hairiness in the sense that a greater length corresponds to less hairiness.
• Cotton yarns are known to be less hairy than yarns spun from man-made fibres. The possible reason for        this is the prifile of the two fibres.Because of taper, only one end, the heavier root part of the cotton fibre,    tends to come out as a protruding end in a cotton yarn. With man-made fibres, both ends have an equal
   probability of showing up as protruding ends.
• If the width of the fibre web in the drafting field is large, the contact and friction with the bottom roller          reduce the ability of the fibres to concentrate themselves and hairiness occurs. This effect is found more in    coarse counts with low TPI. This suggests that the collectors in the drafting field will reduce yarn hairiness.
• The yarn hairiness definitely depends on the fibres on the outer layer of the yarn that do not directly adhere    to the core. Some of them have an end in the core of the yarn gripped by other fibres whereas others,          because of the mechanical properties of the fibre(rigidity, shape, etc.) emerge to the surface. During the
   twisting of the yarn, other fibres are further displaced from their central position to
   the yarn surface.
• Greater the fibre parallelization by the drawframe, lower the yarn hairiness.
• An increase in roving twist results in lower yarn hairiness, because of smaller width of fibre web in the          drafting field.
• The number of fiber ends on the yarn surface remains fairly constant; the number of looped fibers reduces      in number and length on increasing twist.
• Combed yarn will have low yarn hairiness, because of the extraction of shorter fibres by the comber.
• Yarn hairiness increases when the roving linear density increases . Yarn spun from double roving will have     more hairiness than the yarn spun from single roving. This is due to the increased number of fibres in the       web and due to higher draft required to spin the same count.

Drafting waves increase hairiness. Irregularity arising from drafting waves increases with increasing draft. Yarn hairiness also may be accepted to increase with yarn irregularity, because fibers protruding from the yarn surface are more numerous at the thickest and least twisted parts of the yarn.

• The yarns produced with condernsers in the drafting field, particularsly if these are situated in the principal    drafting zone, are less hairy than those spun without the use of condensers.
• Higher spindle speed – high hairiness. When yarns are spun at different spindle speed, the centrifugal force    acting on fibers in the spinning zone will increase in proportion to the square of the spindle speed, causing      the fibers ends as they are emerging from the front rollers to be deflected from the yarn surface to a            greater extent. Further, at high spindle speed, the shearing action of the traveller on the yarn is likely to        become great enough to partially detach or raise the fibers from the body of the yarn. As against the above    factors, at higher spindle speeds the tension in the yarn will increase in proportion to the square of the          spindle speed, and consequently more twist will run back to the roller nip, so that it is natural to expect        that better binding of the fibers will be achieved. The increase in hairiness noticed in the results suggests      that the forces involved in raising fibers from the yarn surface are greater than those tending to incorporate    them within the body of the yarn at higher spindle speeds.
• Higher draft before ring frame-less hairiness. There is a gradual reduction of hairiness with increase in          draft. In other word, as the fiber parallelization increases hairiness decreases. Reversing the card sliver        before the first drawing head causes a reduction in hairiness, the effect being similar to that resulting from    the inclusion of an extra passage of drawing.
• Smaller roving package-less hairiness. Yarn hairiness decreases with decrease in roving (doff) size, and        yarn spun from front row of roving bobbins is more hairy and variable as compare to that spun from back      row of rowing bobbins. It may be noted that though the trends are consistent yet the differences are              nonsignificant:
• The spinning tension has a considerable influence on the yarn hairiness. The smaller the tension,the greater    the hairiness. This is the reason why heavier travellers result in low yarn hairiness If the traveller is too        heavy also , yarn hairiness will increase.
• Spindle eccentricity leads to an increase in hairiness. Small eccentricities influence hairiness relatively little,    but, from 0.5 mm onwards, the hairiness increases almost exponentially with eccentricity.
• The increase in hairiness due to spindle eccentricity, will be influenced by the diameter of ring, dia of            bobbin, the shape of the traveller,the yarn tension, etc.
• Yarn hairiness will increase if the thread guide or lappet hook is not centred properly. Heavier traveler- less    hairiness. The reduced hairiness of yarns at higher traveller weights can be explained by the combined          effect of tension and twist distribution in the yarn at the time of spinning. The spindle speed remains              constant, but the tension in the yarn will increase with increasing traveller weight, and better binding of the    fibers would be expected. Parallel fibers-less hairiness. The improvement of yarn quality on combing is
   mainly ascribed to the reduction in the number of short fiber improvement in length characteristics, and        fiber parallelization. There is a marked difference in hairiness of the carded yarn and the combed yarns,        even with a comber loss of only 5%, but the effect on hairiness of increasing the percentage of comber          waste is less marked. Combing even at low percentage waste causes a marked drop in hairiness relative to    that of the carded yarn. In the case of combed cotton yarns the average value of hairiness decreases with    increase in count, whereas in the case of polyester/ viscose blend yarns the hairiness increases with
   increase in count. In the case of polyester/ cotton blend yarns trend is not clear.
• Flat and round travellers do not influence yarn hairiness, but a greater degree of hairiness was observed        with elliptical travellers and anti-wedge rings.
• Traveller wear obviously influences hairiness because of the greater abrasion on the yarn Yarn hairiness          increases with the life of the traveller.
• Bigger the ring diameter, lower the yarn hairiness.
• Yarn spun in a dry atmosphere is more hairy.
• Hairiness variation between spindles is very detrimental. Because these variation can lead to shade or            appearance variaion in the cloth.
• The variation in hairiness within bobbin can be reduced considerably by the use of heavy travelers alone or      by balloon-control rings with travellers of normal weight. In both the cases yarn is prevented from rubbing    against the separators.
• Yarn hairiness is caused by protruding ends, by the presence of a majority of fibre tails This suggests that      these tails will become heads on unwinding and that friction to which the yarn is subjected will tend to            increase their length. It is therefore logical that a yarn should be morehairy after winding.
• Repeated windings in the cone widning machine will increase the yarn hairiness and after three or four          rewindings, the yarn hairiness remain same for cotton yarns.
• Winding speed influences yarn hairiness, but the most important increase in hairiness is produced by the act    of winding itself.
• Because of winding, the number of short hairs increases more rapidly thatn the number of long hairs.
• In two-for-one twisters (TFO), more hairiness is produced because, twist is imparted in two steps Yarn            hairiness also depends upon the TFO speed, because it principally affects the shortest fibre ends.
• Hairiness varitions in the weft yarn will result in weft bars.

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