Indian Journal of Fibre & Textile Research Vol. 26, December 2001, pp. 366-371

A comparative study of MTS and equivalent MJS yarns

K R Salhotra", S M Ishtiaque & Akshay Kumar Department of Textile Technology, Indian Institute of Technology, New Delhi 110016, Indi a

Received 16 October 2000; 1 November 2000

Murata twin-spun (MTS) yarns have been compared with equivalent Murata jet-spun (MJS) yarns at different ply twi st level s both in Sand Z directions. It is observed that the doubling increases the tenacity, breaking extension and f1exural rigidity of both the yarns. MTS yarns are stronger and less rigid than the equivalent MJS yarns. The percen tage increase in tenacity, breaking extension, and f1exural rigidity is more in MTS doubled yarns. The subjective assessment of fabric han­dle shows that MTS yarn fabrics are softer than MJS yarn fabrics before ancl after fini shing treatment. Finished fabrics are softer than grey and bleached fabrics for both types of yarns.

Keywords: Air-jet spinning, Fabric handle, Murata jet-spun yarn, Murata twin-spun yam, Plying, Polyester/viscose yarn

1 Introduction Ever since the first appearance of the Murata jet

spinners (MJS) at the ATME exhibi tion in 1982, air-jet spinning has expanded in the sector of medium-to-fine yarn counts (synthetics and blends). No matter whether one or two jets are being used, the yarn is held together by wrapping of some fibres around a core of essentially twistless fibres which is twisted temporarily before entering the twisting zone but which is retained essentially twistless in the yam center. The tight wrapping of surface fibres in air-jet yarns, however, leads to harsh handle of fabrics.

The serious problem of the harsh touch and somewhat rugged structure of the finished product was well recognized by the machinery manufacturers. Later, they adapted a jet spinning system, called Murata twin spinner (MTS), in which the outputs from two spinning units, operating on MJS principle, are wound onto a single package as a precursor to two-for-one twisting or ring doubling. The single yam spun in this way has little wrapping which is sufficient to wound as a pair on a package. The resultant yam may derive its tensile strength and other properties from the subsequent folding twist.

The world-wide consumption of two-fold staple yams is second only to single ring-spun yams and far exceeds to that of rotor yams. While the advantages of a two-fold yam are numerous, there have been many attempts to reduce the cost of thi s process, e.g. by

aTo whom all the correspondence should be addressed. Phone: 6591402; Fax: 0091-0 I 1-6561622; E-mail: kr_salhotra@hotmail.com

seeking alternatives to a two-fold yarn (such as siro­spun), by improving the efficiency of the process, and by using minimum folding twist l

.

Till now researchers have paid less attention to two-fold air-jet spun yarn. Little insight has been provided to the extent of improvement after doubling. It is very important to understand the effect of process variables and doubling parameters on the properties of MJS and MTS doubled yarns so as to produce a better two-fold yarn.

In the present work, the characteristics of Murata twin-spun yarn (MTS) have been optimized and then compared with those of the equivalent double Murata jet-spun yarn (MJS). The handle of MJS and MTS yarn knitted fabrics has also been compared before and after finishing treatment.

2 Materials and Methods

2.1 Preparation of Yarn Samples

Single yarn samples of 14.8 tex were spun from the blends of polyester and viscose (65:35) fibres (51 mm length and 1.66 dtex ) on MJS 802 and MTS 881 air-jet machines. The MJS yarn was wound on an assembly winding machine. The parallel wound MJS and MTS yams were twisted on ring doubler with twist factors of 19.1 ,23.9,28.7,33.4 and 38.3 in S direction and 19.1, 28.7 and 38.3 in Z direction respectively.

2.2 Knitting of Yarn Samples

MJS and MTS yarns of optimized twist multiplier were plai knitted on Krenzler maschinen circular knitting machine using the fo llowing parameters:

SALHOTRA el al.: A COMPARATIVE STUDY OF MTS & MJS YARNS 367

Gauge 20, diameter 8.9cm, speed 230 rpm, and tight­ness factor 12.

2.3 Finishing of Knitted Fabrics MJS and MTS yam knitted fabrics were scoured,

semi bleached and finished with three finishing agents respectively. Each of MTS and MJS yam fabrics was preserved after every processing stage for handle assessment.

Scouring was carried out with soda ash (2 gllitre) and soap ( 0.5 g/litre ) for 2 h at 800 C. The scoured fabric samples were then semi bleached with H20 2 (2 g/litre) for 1 h at boiling point. Finishing was done according to the procedure followed by Clariant (I) Sandoz. Ltd. as shown in Table 1.

2.4 Test Methods

2.4.1 Yarn Testing

Yam tenacity and breaking extension were measured on an Instron tensile tester (model 4303) using 500 mm test specimen and a time to break of 20 ± 2 s. The flexural rigidity was measured on Shirley stiffness tester by using ring loop method2

.

2.4.2 Fabric Testing

For subjective assessment, five samples, each of MJS and MTS double yam knitted fabrics (l grey, 1 bleached and 3 finished samples), were given to six judges to rank the fabrics according to their feel. The fabrics were ranked from 1 to 10 (1 the best and 10 the worst). If there was any tie, then the mean of the two samples was taken. Ranks given by six different experts were analysed statistically to judge the agreement in the assessment of fabrics. The coefficient of concordance (W) was calculated to judge the agreement amongst the judges in assessment of fabrics.

3 Results and Discussion

3.1 Single Yarn Tenacity and Breaking Extension The si ngle yam tenacity and breaking extension for

MTS and MJS yarns are shown in Table 2. It may be observed that the yarns spun on MTS possess considerably lower breaking strength than the yarns spun on MJS. Owing to the lower amount of wrapping in the MTS yarn, insufficient transverse forces are generated for adequate inter-fibre friction to prevent fibre slippage in core. On the other hand, the low breaking extension in the MTS yarn is ascribed to the more slippage in the core as compared to MJS yarn.

Table I-Finishing conditions

Yarn Finishing agent

MTS Sandoperm MJS ACH

MTS Sando soft PNLI MJS

MTS Sandoperm ACH MJS +

non-ionic soap

MTS-Murata twin-spun yam MJS-Muratajet-spun yarn

Conc. of finishing

agent g/litre

15

15

15

0.5

Finishing condition

Normal drying

Curing at ISO°C for 45-60 s

Table 2- Single yarn properties

pH

5.5

5.5-6.0

5.5-6.0

Yam Linear density Tenacity Breaking Flexural rigidity tex cN/tex extension , % mNmm2

MTS 14.7 10 6.2 2.92

MJS 14.7 IS.14 9.3 3.S6

3.2 Single Yarn Flexural Rigidity

The flexural rigidity values for MJS and MTS yarns are given in Table 2. The common belief that MJS yarns are more rigid than MTS yarns is found to be true. The higher flexural rigidity of MJS yarn is attributed to the higher incidence of wrapper fibres which limits the freedom of core fibres movement during bending3

.

3.3 Double Yarn Tenacity and Breaking Extension

Table 3 shows the tenacity and breaking extension of yarns plied in S and Z directions. Plying generally enhances the tenacity, irrespective of the direction of plying for both the yarns. In the S direction of ply twist, the tenacity passes through an optimum value. However, for Z direction ply twist, the tenacity continuously decreases as the twist increases (Fig. 1). The breaking extension increases with twist for the MTS yarns and it is generally higher when the ply direction is Z (Fig. 2). For the MJS yarn , though the plying results in some improvement in breaking extension, it does not change much with the change in ply twist. On the other hand, the tenacity for MTS yarn is higher than that of MJS yarn at almost all the twist levels.

The improvement in tenacity, due to doubling, is mainly ascribed to the pressure developed along the contact region owing to the helical arrangement of single yams around each other. This enables greater

368 INDIAN J. FIBRE TEXT. RES. , DECEMBER 2001

Table 3-Effect of doubling twist factor on tensile properties of polyester/viscose (65 :35) MTS and MJS double ya rns (29.5 tex )

Twist direction

S

S

S

S

S

S

Z Z Z

S

S

S

S

S

Z Z Z

25

S Direction 24 --+-- MTS

-4- MJS 23

22

21 --~ 20

Doubling Tenacity twist factor cN/tex

19.1 21.18

23.9 22.16

28.7 23.30

33.4 22.35

38.3 21.76

19.1 21.18

19. 1 21.57

28.7 18.92

38.3 17.94

19.1 21.0

23.9 21.57

28.7 22.25

33.4 21.37

38.3 20.78

19.1 21.08

28.7 18.92

38.3 17.94

_ _ a. ,

-.... --,

~ ~------~-------~--------~-------~

% increase in tenacity Breaking extension, %

MTSYarn

III 121

133

122

117

III

115

88.8

78.8

MJS Yarn

15.8

18.7

22.9

18.0

14.6

16.0

4.40

-1.10

12.5

12

11.5

II <f2. c' .~ 10.5

S Directipn ____ MTS

--G- - MJS

10.9

11 .2

11 .7

11.8

12. 1

10.9

12.2

12.4

14.2

11.0

11.3

11.6

11.8

12.1

11.4

12.2

12.9

9- --

% increase in breaking extension

75 .6

80.4

87 .0

88.6

93.0

75.6

96.1

99.8

127

17.8

21.7

25.1

27.4

29.7

22.8

3 1.3

38.8

<.>

Z. 'u

19.1 23.CJ 28.7 33.4 38.3 c Q)

>< 19. 1 23.9 28.7 33.4 38.3

III ~ 23 ..--______________________________ -.,

Z Direction

21

20

19

18

17 ~ ______________ ~~ ______________ ~

19 . 1 28.7 .18.3 Tex twist factor

Fig. I-Vari ation in double yarn tenacity with twi st

Q)

Ol c 14.5 :.;;: III ~

CD 14

13.5

I ]

12.5

12

11.5

II 19.1

Z Direction

~8.7 .18.3 Tex twist factor

Fig. 2-Variation in doub le yarn break ing c:xlension wi th Iwist

SALHOTRA et al.: A COMPARATIVE STUDY OF MTS & MJS YARNS 369

inter-fibre cohesion wherein even the surface fibres contribute towards tenacity. The surface wrapper fibres in single yarns are wrapped in Z direction. As the ply twist in the S direction is introduced, the individual strand rotates on its own axis, causing Z­wrapped surface fibres to untwist and initially becomes loose. The increase in ply twist keeps untwisting the surface fibres up to a point after which it causes reverse twist in the surface fibres. As a result, these fibres gradually become taut and start reinforcing the structure4

•

Table 3 shows that for weaker MTS single yarns, the improvement in tenacity is much higher (up to 133%) than the stronger MJS yarns (up to 22.9%). This is because in MTS air-jet machine, two single air-jet yarns are given as much strength in spinning as is necessary for their subsequent trouble-free assembly winding and

• • 3 tWlstmg" .

At a low ply twist level in the S direction, the tenacity is low since many surface fibres, on becoming loose, may not contribute in reinforcing the structure. At a plying twist factor of 28.7, the reinforcing effect of the surface fibres and mutual support of helically twisted core fibres become most effective, resulting in maximum strength. Beyond this optimum twist level, the tenacity decreases mainly owing to the well-known obliquity effect in the core fibres. In the case of Z-ply twist direction, the Z-wrapped sUlface fibres are twisted in the same direction from the beginning and start becoming taut. The reinforcing effect of the surface fibres becomes effective right in the beginning and thus produces the strongest yarn at a ply twist factor of 19.1 (Fig. 1). The strength decreases thereafter because of the over twisting of surface fibres which may cause some of them to break and lead to weakening of the structure to such an extent that it may not be compensated by the support originating from the helically wrapped configuration of the core4

•

The increase in breaking extension due to the plying is attributed to the helical arrangement of the majority of core fibres and reduction in the number of weak places as a result of their mutual support. With the increase in ply twist, the breaking extension also increases due to the well-known effect of obliquity on majority of core fibres. The fact that ply twisted yarns produced from the similar direction of twist to their spun twist yams possess more extensibiliti also holds true here (Fig. 2).

The percentage increase in breaking extension of MTS double yam is more than that of MJS double yarn because of the similar reason as given in case of tenacity. However, the higher tenacity and breaking extension of MTS double yams as compared to those of the MJS double yams are attributed to the relatively higher proportion of almost parallel an'angements of core fibres in the MTS yams which leads to the better utilization of fibre properties6

.

3.4 Double Yarn Flexural Rigidity

Table 4 shows the flexural rigidity of MTS and MJS double yams. The flexural rigidity was measured up to a twist factor of 28.7 in Z direction. Beyond this twist level, the yarn was too twist-lively to form a stable loop. Doubling increases the flexural rigidity. However, the flexural rigidity first decreases with the increase in doubling twist (S direction) from 19.1 to 28.7, and than increases slightly on fUlther increase in twist factor from 28.7 to 38.3 (Fig. 3). This decreasing trend in flexural rigidity can be ascribed to the geometrical form of majority of core fibres, which are helical in nature in a plied structure4

. Further, the increase in flexural rigidity may be attributed to the reinforcing effect of the sUlface fibres and the mutual support of the helically wrapped core fibres.

The flexural rigidity is higher for the Z-ply twisted yam than that for the S-ply twisted yarn (Fig. 3). Since the restriction imposed by Z-wrapped sUlface fibres is

Table 4--Effect of doubling twist factor on flexural rigidity of MTS and MJS double yams

Twist direction

S S

S

S

S

Z

Z Z

Doubling twist factor

19.1

23.9

28.7

33.4

38.3

19.1

28.7

38.3

MTS double yarn Flexural rigidity %

mNmm2 increase

4.54 55.5

4.27 46.3

3.83 31.2

3.92 34.2

4.12 41.1

4.93 68.8

4.20 43.8

MJS double yam Flexural rigidity %

IllNmlll2 increase

4.96 28.5

4.80 24.4

4.50 16.6

4.52 14.5

4.57 18.4

5.27 36.5

4.98 29.0

370 INDIAN 1. FIBRE TEXT. RES ., DECEMBER 2001

4.9

4.7

4.5

4.3

4.\

3.9 N

~ 3.7 Z

--- --<1 ....

..... , "

S Direction -+--MTS _ ... _MJS

" .... ~ ___ - - fJ- - - - ---

E 3.5 L-__ --L ___ --L-___ .L-__ --L-.--J

~ '0

\'J .\ 2.1.9 28.7 33.4 38.3 '0, .;::

ro :J 5.4 X Z Direction Q)

u:: 5.2 - -- --- --- ---------4.H

4.6

4.4

4 .2

19. 1 Tex twist factor

28.7

Fig. 3-Vari ation in double yarn flexural rigidity with twi st

greater when the twist direction is also Z (being tighter in nature), the flexural rigidity is expected to be higher in the Z-ply twisted yarn than that in the S-ply twisted yarn. Table 4 also shows that the flexural rigidity of MTS double yarn is lower as compared to its counterpart. This can be ascribed to the lower flexural ligidity of MTS single yam. However, the percentage increase in flexura l rigidity (up to 68.8%) of MTS double yam is higher. This is because in MTS yam the slippage in single yam core is restricted due to the increased cohesion after doubling.

3.5 Knitted Fabric Handle

The results of subjective assessment can'ied out for grey, bleached and fi nished MTS and MJS yam knitted fabrics made from optimized twist factor of 28.7 in S direction are shown in Table 5. It is observed that at all the stages MTS yarn knitted fabric is softer than MJS yam knitted fabric . This can be attlibuted to the stiffer single and double MJS yarns as compared to MTS yams which impatts a harsh feel to the MJS fablic. It can also be observed that the finishing treatment softens the fabric in both the cases. This is due to the heat treatment given during the finishing which dissipated the internal

Table 5-Subjective assessment of grey, bleached and finished MTS and M1S yarn knitted fabrics

Type of fabric Treatment given Rank"

MTS Sandoperm ACH

+ non-ionic soap

MTS Sandoperm ACH 2

MTS Sandoperm PNLI 3

M1S Sandoperm PNLI 4

M1S Sandoperm ACH 5

M1S Sandoperm ACH 6 + non-ionic soap

stresses, leading to softness to the fabric. The improvement in fabric hand is also due to the deposition of finishing agent on the fabric surface during finishing treatment which, in tum, smoothens the surface7

.

However, the extent of effect of the finishing agent is not clear. The calculated value of coefficient of concordance (W= 0.835) shows a good amount of agreement amongst the judges in assessing the fabric handle. A test of significance (at 1 % level) was also carried out and a real measure of agreement was found between the final ranking.

4 Conclusions 4.1 MTS single yarn is considerably weaker, less

extensi ble and exhibits lower flex ural rigidity than the MJS single yarn.

4.2 Doubling increases the tenacity, breaking extension and flex ural rigidity of both MTS and MJS yarns.

4.3 MJS and MTS two-fold yams give maximum tenacity wi th plying twist factor of 28.7 in S di rection. The increase in tenacity, breaking extension and flexural rigid ity of MTS yarns due to doubling is much higher than that in case of MJS yams.

4.4 MTS double yarns, produced by using different ply twist factors in Sand Z directions, are stronger, more extensible and less rigid than their MJS counterparts.

4.5 At doubling twist factor of 28.7, both MTS and MJS two-fold yarns show minimum flex ural rigidity.

4.6 Fabrics made from MTS yarn are softer than the MJS yarn fabrics before and after finishing. Fin-

SALHOTRA et al.: A COMPARATIVE STUDY OF MTS & MJS YARNS 371

ished fabrics are softer than grey and bleached fabrics for both types of yarns.

Acknowledgement

The authors acknowledge the help of Dr. S. Dhamija, Senior Lecturer, The Technological Institute of Textile & Sciences, Bhiwani , for providing mate­rial to carry out the research work.

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Res, 22 (1997) 8. 7 Sharma I C, Chatterjee K N & Mukhopadhyay A K, Indian J

Fibre Text Res, 22 ( 1997) 176.