PRACTICAL HINTS

Causes and consequences of hairy yarn
by
Dr. H.R. Sheikh
Professor, Textile Institute of Pakistan

One of the most important differences between continuous filament yarns and yarns spun from staple fibres in that the letter are hairy. Yarn with fibre mends and loops protruding out from the main body are classed as hairy yarns. In the fairchild's Dictionary of Textiles (1) hairiness has been described in general as a condition of yarn or fibric caused by numerous loose ends projecting from the surface. ASTM describes hairiness with respect to raw silk as a condition of yarn when there are numerous loose ends of cocoon filaments project from the surface.
Hairiness in yarns is generally produced under high speed spinning and winding conditions.
1. Causes of yarn hairiness
Eadie Bros & Co. Ltd. Of U.K. have reported causes of yarn hairiness in their hard book for folange Ring users. Some of these causes are described as follows:
(i) Most common cause of yarn hairiness is marginal fibres of the drafted roving ribbon escaping twist as it emerges from the front drafting roller nip. Some of these fibres are lost as fly while others have only one end incorporated in the yarn body. The other end protrudes out and yarn produces hairy. Failure of the marginal fibres to get twisted fully into the yarn is mainly due to short spinning triangle or application of high draft or both low spinning tension resulting from the use of two light traveller also contributes to yarn hairiness.
(ii) If the relative humidity is not at optimum level, fibre exhibit a tendeny to stick on the surface of drafting rollers which produces hairiness in the yarn.
(iii) Non-uniform rotation of the travellers because of worn-out rings, ribration of spindles because of worn-out or slipping tapes or tra becoming leaded with waste.
(iv) Trapping of the yarn between the traveller and top of the ring flange.
(v) Traveller seraps the yarn when traveller number is not correct with respect to the count of yarn being spun.
(vi) Yarn balloon lash on the separator plates.
Yarn hairiness can be minimised by optimising the above listed spinning conditions at the spindle point. It is also necessary to monitor and monomise the short fibre content in the sliver and roving at the spinning preparatory processes to reduce hairiness.
2. Measurement of yarn hairiness
Hairiness of yarn is measured by photoelectric sensors. The sensors not only details and counts the number of fibres protruding from the yarn body in excess of 2 m.m. but also estimates the total length of all such fibre present in the totoal length of yarn tested. The hairiness measure is given in the from of a number which is derived automatiocally by the sensors so ratio of the total length of the producing fibres and the total length of the yarn testes wap from soll [2] reports that OS-sensor is included in the optico-electronic sensor supplied with the fourth generation of Uster® Tester - 4 5 X and measures hairiness of yarn.
3. Consequences of Hairiness
3.1 In the manufacture of leisure user especially for textiles worn in contact with skin yarn hairiness is an excellent characteristics as it influences touch, feel and wear quality of fabrics ( 2). However, hairy yarns also give rise to adverse consequences in the textiles produced from such yarns.
3.2 If the hairiness is more than 5, the fabrics will exhibit pilling tendency.
3.3 Excessive hairiness of yarn contributes to appearance of barre' in fabrics woven or knitted from such yarns upto about 10% as estimated by Yankey (3).
In conclusion it may be stated that the wet processors accept only the "Barre" free fabrics for pre-treatment processes, mercerizing dying, printing and finishing for creation of beautiful fabrics for local of the export markets. It is, therefore, essential for the spinners to monitors and control hairiness of yarn to facilitate the production of "Barre" free fabrics by the weavers and the knitters.
Acknowledgement
Technical information received from shortages Aslam Khan, and Mr. Naeem Khalid during the preparation of the paper if gratefully acknowledged.
References
1. Isabel B. Wingate, "Fairchild's Dictionary of Textiles".
2. Wolfram Soll, " Uster® Symposium 2004: from Fibre to Fibre, " Pakistan Textile Journal, February, 2003.
3. Joseph M. Yankey, "The solution for controlling fabric barre", 1996n Beltwide cotton conference, USA.