K Ramachandralu, Non-member B S Dasaradan, Non-member

It is a well known fact that high speed spinning today has spinning system combines air jet and ring spinningachieved excellent results in terms of productivity, but has not technologies. Cotton being a finer and shorter fibre woulddone satisfactorily on yarn quality, especially in terms of the present more ends per unit length, which increases the numberimportant characteristic namely hairiness. The ability of the of fibres protruding out of the yarn surface and affects itsspinner to keep the hairiness under control during spinning surface and structural properties. Hence, it has beenwould help him to minimise the increase in imperfections in considered for this research work which makes an attempt onwinding. The fibres can be bound into the yarn only if there studying the effect of air vortex ring spinning system oncan be a mechanism before the fibre strand is delivered out of reduction of hairiness and improvement of other properties ofthe front roller nip, as in the compact spinning³. Otherwise a cotton yarn. Further, it examines the effect of direction ofmechanism which can influence the fibre strand in such a way rotation of the air vortex produced by the swirling air currentthat the surface fibres are bound inside the yarn is required.

on the hairiness and other properties of yarn.

METHODOLOGY

yarn by the upward swirling air against the yarn movement and twist, which facilitates the tucking of protruding fibres

Materials and Method

into the body of the yarn by loosening and tightening up of the A roving of 1.2 hank was produced in the usual manner andfibre strand. Hence, the utility of air jet has to be considered taken for this study. The ring spinning process parameters are given below in Table 1.

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Figure 1 Air vortex ring spinning system Table 1 Ring spinning process parameters

Design and Fabrication of Air Jet Nozzle

Two air jet nozzles were designed and fabricated for this study. They are similar in all dimensions, but different in the direction of inclination of the orifices. Type 1 nozzle will produce air vortex in the direction same as that of air twist, ie, in Z direction. Type 2 nozzle will produce air vortex in the direction opposite to that of yarn twist, ie, in S direction. A suitable air jacket with inlet for compressed air to surround

Table 2 Properties of parent yarn spun without using air jet nozzle Figure 2 Design of air jet nozzle assembly

these nozzles was designed and fabricated. This schematic diagram of the air jet nozzle assembly comprising of the air jet nozzle and the air jacket is shown in Figure 2.

RESULTS AND DISCUSSION

Table 2 given below lists the properties of parent yarn spun without using the air jet nozzle.

Table 3 given below lists the properties of yarn produced with the two types of nozzle.

It is observed from Table 3 that the employment of air jet nozzle contributes to hairiness reduction and that the hairiness has got a bearing on the type of the nozzle with respect to the direction of rotation of vortex.

The comparison of properties of yarns namely hairiness, tenacity, elongation, evenness and imperfection using air jet nozzles (both types) with those of the parent yarn are depicted in the form of histograms in Figures 5, 6, 7, 8 and 9.

Effect of Direction of Rotation of Air Vortex on Hairiness

Analysis of test results shows that employment of air jet nozzles reduces the hairiness level in the yarn, and the quantum of reduction is more with Type 1 nozzle when compared to that achieved with Type 2 nozzle. The comparison of air vortex ring spun yarns with parent yarn with respect to hairiness is shown in the form of histogram in Figure 5.

Figure 3 & Figure 4 Air vortex in Z direction and air vortex in S direction respectively

Table 3 Properties of air vortex ring spun yarns

No. of hairs above3 mm/Km

22

U, %

21

15.5

15

14.5

20 19

Tenacity (g/tex)

22

21

20

19

2200

2000

1800

1600

The hairiness reduction with Type 1 nozzle is 50.6%, whereas

the hairiness reduction with Type 2 nozzle is 27.4%. The reduction of hairiness observed in the study requires an

explanation. In general, the ring spun yarn has more fibre ends protruding in the trailing direction^4,5. When the yarn passes

Figure 7 Comparision of air vortex ring spun yarns with parent yarn with respect to elongation

through the nozzle it encounters with the air vortex created by the upward swirling air current, gyrating in the opposite direction. In case of Type 1 nozzle the air vortex false-twists the partially twisted yarn in the direction same as that of yarn twist, ie, in Z direction which is schematically shown in Figure 3. This air vortex produced by the upward swirling air current tucks the protruding fibres, particularly the trailing hairs, onto the yarn surface. When the yarn comes out of the

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nozzle the tucked hairs are bound into the yarn structure as the mechanical twist created by the revolving traveller flows towards the nozzle. The sweeping action of the air vortex, which effects in the realignment of the fibres, contributes greatly to reduced hairiness. In case of Type 2 nozzle, the air vortex produced by the upward swirling air current false-twists the partially twisted yarn in the direction opposite to that of yarn twist, ie, in S direction, which is shown schematically in Figure 4. The upward swirling air current against the movement of yarn and twist, loosens the fibre strand, when by the tucking of fibres on to the body of the yarn takes place. As the yarn comes out of the nozzle the loosened fibre strand gets tightened by the flow of twist from the mechanical twisting agency, when by the binding of the tucked fibres takes place as explained by Wang, et al² in their study of air jet spinning. The reason for achievement of better reduction with Type 1 nozzle could be due to the better wrapping of protruding fibres by the sweeping and binding action of the air vortex current twisting the strand of fibres in the direction same as that of the yarn twist.

Effect of Direction of Rotation of Air Vortex on Tensile Properties

The test results on tensile properties are given in Table 3 and the comparison of air vortex yarns with parent yarn with respect to these properties are shown in the form of histograms in Figures 5 and 6. The test results show that the employment of Type 1 nozzle increases the tenacity and elongation percentage marginally by 4% and 7.3%, respectively over parent yarn, where as with the employment of Type 2 nozzle there is not much difference in the tensile properties over parent yarn. This could be explained as follows: with Type 1 nozzle there is a reduction of 50% in hairiness. This substantially reduced hairiness in the yarn structure makes all the component fibers to share the tensile load which results in increased tenacity as well as elongation percentage, which is in fair agreement with the general theory. In case of Type 2 nozzle, even though there is a reduction of hairiness to the tune of 27.4%, it has not resulted in any significant improvement in tensile properties.

Effect of Direction of Rotation of Air Vortex on Evenness and Imperfections

The test results on evenness and imperfections are given in Table 3 and the comparison of the air vortex yarns and parent yarn is given in Figures 7 and 8. They show that there is marginal difference in evenness between the parent yarn and air vortex ring spun yarn, produced with Type 1 nozzle and very little difference between the parent yarn and the air vortex ring spun yarn produced with Type 2 nozzle.

With respect to imperfections it could be noticed that the reduction in imperfections level works out to 11.5% with the Type 1 nozzle whereas there is very little reduction (3.85%) with Type 2 nozzle. Probably the substantial reduction in hairiness with Type 1 nozzle has reduced the imperfections level as better wrapping of the protruding fibres could have covered up the imperfections present in the yarn to certain extent.

CONCLUSION

1. Air vortex ring spinning system in general improves the quality of cotton yarn with marked reduction in hairiness.
2. Air vortex ring spinning system fitted with air jet nozzle creating the air vortex in the direction same as that of the yarn twist gives better results in terms of hairiness reduction, increase in tenacity and elongation and reduction in imperfection level when compared to that with the air jet nozzle creating the air vortex in the direction opposite to that of the yarn twist.

ACKNOWLEDGEMENT

The authors are thankful to the Management, Principal and Head of the Department of Textile Technology, PSG College of Technology, for providing all the facilities and encouragement to carry out this research work successfully.

The authors gratefully acknowledge the Management of The Lakshmi Mills Company Ltd, for permitting them to carry out the trials at their Palladam unit, and its Vice President (Technical), General Manager and the Technical Officers for providing all logistics and support without which this research work would not have been completed successfully.

The authors profusely thank Dr V Subramanian, Chair Professor, Anna University, Chennai for the useful discussion on this study.

REFERENCES

1. A R Kalyanaraman. ‘A Process to Control Hairiness in Yarn.’ Journal of Textile Institute, vol 83, no 3, 1992, pp 407-413.
2. X Wang, M Miao and Y L How. ‘Studies of Jet Ring Spinning, Part I : Reducing Yarn Hairiness with the Jet Ring.’ Journal of Textile Research, vol 67, no 4, 1997, pp 253-258.
3. Rieter’s Brochure on Com 4 Spinning System.
4. A Barella. ‘The Hairiness of Yarns.’ Textile Prog, vol 13, no 1, 1983.
5. K P R Pillay. ‘A Study of The Hairiness of Cotton Yarns, Part I : Effect of Fibre and Yarn Factors.’ Journal of Textile Research, vol 34, 1964, pp 663-674.