Tensile, Evenness & Hairiness Characteristics Of Manifold Ring Spun Yarns

1. Introduction

The effect of twist on the tensile properties of singles & two fold yarns have been investigated by several research workers. However, corresponding information on manifold ring spun yarns is extremely rare in literature. Due to the complex nature of single and folded yarn relationships, there is a definite practical importance in the effect of twist on the tensile & evenness properties of folded yarns. Hence, an adhoc study has been carried out in this connection at SITRA covering folded cotton and manmade fibre (MMF) yarns with as many as 5 ends in the twisted structure.
The major findings of the study are given in this paper.

2. Details on folding trials

3 cotton yarns and two manmade fibre yarns were taken for the study. The experimental plan is given in Table 1.

Where,

L = 50% span length of cotton (mm)
F = Mic. value of cotton (g/inch)

3. Tensile properties of ring spun folded yarns

3.1 Tenacity

Tenacity values of ring spun folded yarns at various D/S ratios are given in Table 2 and are graphically represented in Figure 1 for cotton yarns.

In the case of 2 ply yarn, the folded yarn tenacity increases continuously with folded yarn TPI. However, in 3 ply & 4 ply yarns, maximum folded yarn tenacity is realised at a D/S ratio of 1.0. With further increase in twist, tenacity of folded yarns tends to fall down. In 5 ply construction, maximum folded yarn tenacity was achieved at 0.6 to 0.7 of a D/S ratio and afterwards, the tenacity falls with increase in twist. This phenomenon could be probably due to assymetrical distribution of ends when the number of ends in the folded structure is high.

Maximum folded yarn tenacity is higher than that of single yarn tenacity by 5 to 15% in 20s K, 20 to 35% in 40s C and 15 to 30% in 60s C (Table 3).

The higher strength realisation in combed yarns after doubling could be due to higher mean fibre extent and better packing in those yarns.

3.2 Breaking elongation of ring spun folded yarns

Breaking elongation values of ring spun folded yarns at various D/S ratios are given in Figure 2.

In the case of breaking elongation, there is a continuous improvement with increase in folded yarn TPI in all the 4 folded constructions.

During tensile testing, the contracted length of yarn has to be straightened first, before the yarn is subjected for loading. Higher the yarn contraction, greater will be the measured value of yarn elongation and vice versa. With increase in TPI, higher will be the yarn contraction and this accounts for the observed increase in yarn elongation with increase in folded yarn TPI. Folded yarn elongation is higher than that of single yarn elongation by 2.5% - absolute (2 ply) to 8.0% - absolute - (5 ply) in 20s K. In 40s C and 60s C yarns, the corresponding difference is 2.0% - absolute (2 ply) to 6.5% - absolute (5 ply).
20s K yarn, which had exhibited relatively lower strength realisation, after doubling had shown higher elongation increase after folding.

4. Evenness characteristics of folded cotton yarns

Evenness & imperfections values of folded cotton yarns are shown in figures 3 & 4.

With increase in the number of ply, the evenness of cotton yarns improves continuously, the improvement being of the order of 3.5 U% - absolute (2 ply) to 7.0% U% - absolute - (5 ply) in the case of 20s K, 2.5 U% - absolute - (2 ply) to 5.5 U% - absolute - (5 ply) for 40s C and 3.0 U% - absolute - (2 ply) to 6.0 U% - absolute - (5 ply) for 60s C. However, with increase in D/S ratio, there is no appreciable change in evenness values irrespective of the number of ply.

The various yarn imperfections in single yarns reduce by over 90 to 95% in different counts after doubling. Maximum reduction in yarn imperfections occurs in 2 folded construction itself. As in the case of evenness, increase in D/S ratio do not significantly alter the incidence of imperfections in different ply yarn constructions.

5. Hairiness properties of ring spun folded yarns

Hairiness values of single and folded yarns were measured using Zweigle Hairiness Tester (S3 value* Hairs/100 m). With increase in folded yarn TPI, S3 value tends to fall down. Maximum reduction in S3 value occurs at a D/S ratio of 1.0 and afterwards, the reduction is only marginal.

Similarly, quantum reduction in hairiness was observed in 2 ply construction itself and afterwards the reduction is only marginal. Reduction in S3 value for different levels of D/S ratio is given in Table 4 for 40s CW & 60s CW yarns

6. Tensile characteristics of man-made fibre (MMF) yarns after folding

6.1 Tenacity

40s yarn from 100% viscose and 20s yarn using 100% polyester were also spun using modern machinery. Then they were folded up to 5 ply construction with different D/S ratio and their tensile characteristics studied. Tenacity (cN/tex) values of the two yarns are shown in Figure 5.

In contrast to what was observed in cotton yarns, for man made fibre yarns, maximum tenacity was established at D/S ratio of 0.6 to 0.7 for all the folded yarn constructions and with further increase in D/S ratio, tenacity shows a tendency to fall down. There is not much of a difference in tenacity values obtained for 2 ply, 3 ply, 4 ply and 5 ply constructions. Tenacity obtained for 40s viscose plied yarn is higher than that of single yarn by about 10%. In the case of polyester yarns also, the strength difference between single & plied yarns is of the same order.

The tenacity increase due to folding is relatively low in MMF yarns as compared to that in combed cotton yarns. This could be due to better fibre length utilisation in MMF yarns in single yarn stage itself due to fibre length uniformity. In view of this, MMF yarns offers only less scope for tenacity enhancement through folding.

6.2 Breaking elongation

As in the case of cotton yarns, elongation values of MMF folded yarns considerably increases with increase in folded yarn TPI (Figure 6).

The difference in elongation values (absolute values) between single & folded MMF yarns at different ratios are given in Table 5.

Increase in elongation due to doubling is found maximum for 4 ply construction both for viscose as well as polyester yarns.

7. Hairiness properties of MMF folded yarns

In the case of MMF yarns, there is a continuous reduction in S3 value with increase in the number of ply. Maximum reduction in S3 value occurs at a D/S ratio of 1.0 and afterwards, the reduction is only marginal. Reduction in S3 values for different levels of D/S ratio is given in Table 6 for 40s viscose and 20s polyester.

The extent of reduction in hairiness due to folding in MMF yarns is of the order of 70 to 75%.

8. Conclusions

The major conclusions of the study are as follows:

1.In cotton yarns, the folded yarn tenacity increases continuously with folded yarn TPI in 2 ply construction. In 3 ply & 4 ply yarns, maximum folded yarn tenacity is realised at a D/S ratio of 1.0. In the case of breaking elongation, there is a continuous improvement with increase in folded yarn TPI in 2 ply, 3 ply, 4 ply as well as 5 ply constructions.
2.The evenness of cotton yarns improves continuously with increase in the number of ply. However, with increase in D/S ratio, there is no appreciable change in evenness values irrespective of the number of ply. The various yarn imperfections in single yarns reduce by over 90 to 95% in different counts after doubling.
3.With increase in folded yarn TPI, hairiness in cotton yarns tends to fall down. Extent of reduction in hairiness due to folding is of the order of 90% for cotton yarns.
4.For man-made fibre yarns, maximum tenacity is realised at a D/S ratio of 0.6 to 0.7 for all the folded yarn constructions. There is not much of a difference in tenacity values obtained for 2 ply, 3 ply, 4 ply and 5 ply constructions.
5.In the case of MMF yarns, there is a continuous reduction in hairiness with increase in the number of ply. The extent of reduction in hairiness due to folding is of the order of 70 to 75%.

8. Acknowledgement

The authors are thankful to Dr. Arindam Basu, Director, SITRA for his guidance at various stages of preparation of this paper. Thanks are also due to Ms. Indra Doraiswamy, Research Advisor, SITRA for her valuable suggestions, which has helped the authors to consolidate the ideas put-forth in this paper. Our special thanks are due to Mr.R.Pasupathy, Textile Physics Division, SITRA for his help in completing the various quality evaluation trials reported in this paper in time.

9. References

1. K.R. Salkotra and R.B. Dutta
Influence of residual twist in single yarns on the tensile strength of 2-ply yarns
Indian Journal of Textile Research, Vol.6, No.3, September 1981, p. 109 112

2. N.K.Palaniswamy & A. Peer Mohamed
Balanced two ply cotton yarn
Indian Journal of Fibre & Textile Research, Vol.30, No. 1, March 2005, p. 32 36

3. N.Tarafdar & Dr.S.M. Chatterjee
Role of twist in relation to properties of two ply cotton yarn
Textile Trends, Vol.31, No.2, May 1988, p.49 57

4. K.B.Krishnan, K.P.R.Pillay and T.Balamuralikrishna &
P. Chellamani and P.K. Abraham
A comparative study of the tensile properties of manifold open-end and ring spun yarns
Proceedings of the 30th joint tenchnological conference held at ATIRA, Ahmedabad during February 1989, p. 18.1 18.8

5. Schwarz E.R.
Structure of plied yarns
Textile Research Journal, Vol.10, 1950, p.175

Source: SITRA - The South India Textile Research Association, Coimbatore