Indian Journal of Fibre & Textile Research Vol. 30, September 2005, pp. 290-294

Low-stress properties of mercerized cotton ring- and

OE rotor-spun yams

G K Tyagja The Technological Institute of Textiles & Sciences, Bhiwani 1 27 02 1 , India

and

Dhirendra Sharma ML V Textile Institute, Bhi lwara 3 J J 00 J , India

Received 18 November 2004; accepted 8 December 2004

Th� effect of yarn l inear density, yarn structure, twist factor and rotor speed on low-stress properties of mercerized cotton

.rmg- and rotor-spun yarns has been studied. For both ring- and rotor-spun yarns, the initial modulus at 1 % and 3%

e�te�slons, packing de�s �ty and hairiness change markedly as a result of mercerization treatment. Flexural rigidity i ncreases slgl1lficantl�, �owever It IS considerably lower for ring- spun yarns. The abrasion resistance of both types of yarns decreases but yarn tWist mcreases It.

Keywords: Cotton, Flexural rigidity, Initial modulus, Mercerization, Ring-spun yarn, Rotor- spun yarn, Twist factor

fPC Code: Int. C1.7 D06H3/00, D06M l llOO, GOIN33136

1 Introduction Mercerization is an established chemical process

for enhancing tensile strength, dyeability and l uster of cotton products. A perusal of the li terature reveals that many of the previous investigations dealt almost ex­clusively with the mechanical properties 1 -4 . The rela­tionships between mechanical properties and spinning factors, such as fibre composition, twist factor and draft, have also been studied5 . In a recent investiga­tion, Dhanda6 assessed the knittabil ity of mercerized ring- and rotor-spun yarns produced with varying twist and rotor speed. There is no report on the low­stress behaviour of mercerized cotton yarns. The low­stress properties of yarns are the major factors l imit­ing their processibility and end-use performance. Be­sides, fabric handle is also affected by the yarn low­stress properties. Consequently, the low - stress re­sponse of mercerized cotton yarns needs to be ascer­tainedThis paper aims at investigating the low-stress properties of cotton ring- and rotor-spun yarns . To gain a better insight into the phenomenon, a range of rotor-spun yarns have been produced with varying twist factor, yarn l inear density and rotor speed.

"To whom all the correspondence should be addressed: Phone: 24256J ; Fax: +9 1 - 1 664-243728; E-mai l : drgktyagi@rediffmail.com

2 Materials and Methods

2.1 Preparation of Yarn Samples

J-34 cotton (2.5% span length, 24.3 mm; micro­naire, 4.2; tenacity at 3 mm stelometer gauge, 1 9.8 g/ tex) was processed on a Lakshmi Rieters blow room line and carded on a MMC card.The carded sliver was given two passages on a Lakshmi Rieters draw frame DOI2S to produces a finished s liver of 2.5 ktex. This sliver was spun i nto yarns (29.5 and 59 tex) on Ingol­stadt rotor spinner RUI I /RU80 (4602) operating un­der normal mill conditions. The process parameters used to produce these yarns i nvolved a 48 mm rotor operating at 833.33 and 1 000 rps speeds, an opening roller speed of 1 00 rps and twist factor of 40. ] 9, 44.02,47 .85 and 5 1 .67. To produce equivalent ring yarns, the drawn sl iver was converted into a suitable rove of 1 .5 hank on a Texmaco Howa Simplex and then fed to a Lakshmi Rieters ring frame G5/1 using a spindle speed of 1 2500 rpm.

2.2 Mercerization Treatment

Mercerization was carried out in a hank merceriz­i ng machine using 25% sodium hydroxide solution. After mercerization for 1 20 s at room temperature, the skeins were stretched to 2% of their original length . The skeins were i nitial ly washed on the ma-

TY AGI & SHARMA: MERCERIZED COTTON RING- & ROTOR-SPUN YARNS 29 1

chine itself, neutralized with 2 % sulphuric acid, thoroughly washed and then dried under atmospheric conditions .

2.3 Tests

All the yarns were tested for initial modulus on an Instron tensile tester (Model 44 1 1 ) according to ASTM D2256 procedure. An average of 50 tests in each case was taken. Yarn hairiness was recorded by Zweigles hairiness meter (Model 0565). Flat abrasion resistance was determined by Custom scientific tester and the yarn flexural rigidity on a weighted ring yarn stiffness tester using ring loop method. The packing density (K) of the yarn was calculated using the fol-lowing expression:

-

K = ( 1 .274 T x 10-5) / P d2

where T is the linear density of yarn (tex); p, the fibre density (g/cm3); and d, the average diameter (cm) of yarn measured using projection microscope.

3 Results and Discussion

The influence of yarn type, yarn l inear density, treatment, rotor speed and twist factor on low­stress properties was studied for significance using analysis of variance (Table I ) ; the confidence level used was 99%. Only first order interactions were con­sidered.

3. 1 Initial Modulus

One of the tensile measures that greatly concerns yarn users is initial modulus. In general, initial modulus refers to the resistance offered by the speci­men for small extensions. High modulus indicates the inextensibility, while low modulus denotes the great extensibi lity of yarns during tensile loading. Figs 1 and 2 display initial modulus data for various cotton yarns. Expectedly, the rotor-spun yarns possess lower initial modulus at 1 % strain level than the ring-spun yarns, and it has different values for different twist factors. However, for all twist factors, the initial modulus increases significantly with the increase in rotor speed due to the decrease in yarn breaking ex­tension. The impact of yarn linear density is also along the expected lines, a higher yarn l inear density results in a lower modulus. On increase in twist fac­tor, the modulus first increases significantly and then decreases. When these yarns are mercerized with so­dium hydroxide, the modulus of both types of yarns shows an ascending trend at all levels of twist. For

Table I-ANOVA test results

Process Yarn EroEert � variable Initial Flexural Abrasion Hairiness Packing

modulus rigidity resistance coefficient 1% Extn 3% Extn

A S S S S S S

S S S S S S S

C S S S S S S

D S S S S S S

A"'C S Ns S Ns S S

A"'S Ns Ns S Ns S S

A"'D Ns Ns Ns Ns Ns Ns

S"'C Ns S Ns S Ns Ns

B"'D Ns Ns Ns Ns S Ns

C"'D Ns Ns Ns Ns Ns Ns

A"'B"'C Ns Ns Ns Ns Ns Ns

B"'C"'D Ns Ns Ns Ns Ns Ns

C"'D"'A Ns Ns Ns Ns Ns Ns

S- Significant at 99% confidence level; and Ns - Non- significant at 99% contidence level. A - Yarn l inear density. B -Treatment. C-Rotor speed. and D -Tex twist factor

500 T""-------- -- - --- _. ---- - - --- -- -----------,

400

300

c;j 0 '" �

� Mlnlt �lln « i,,'), ) � Kln£ )"m (Mell:C'rl/.:d, ED RolOI )" fn, IH.H rr� (GICOY) 8 R�Of )"I,n, IH.H rp$ (MG,cC'li1.�d) • RUIOf ,"Mn, 1(1)0 II''' (Cire),1 • R040f �;1fn. 1000 fPJ (PI.·tCI(C'I I/c:d)

;; 500 ,--------------�--� "8 Yarn Ie,. SQ 0 E

400

300

200

1 00

o 40. 19 44.02 47.85 51 .67

Tcx twi�;t factor

Fig. I -Variation in initial modulus ( I %) with tex twist factor

292 INDIAN J. FIBRE TEXT. RES., SEPTEMBER 2005

500 �---------------- ' ----------� \'U" Ie •• 29.5 � Mint oatn (Gre), 1 400 [D Roool r"n. I)).).1 'v' (GI"r) B R .. ", Y'''. Ill.l) "" IMtI",,,«I)

• M040r yarn, 1000 rp' (Gr"(y) • R(l4Of )'M", 1000 .'PI' (Mc:rc:c.ilcd) 300

200

1 00

o

500�------------------------------� YUIl le .•. 59 U 400

] :.5 300

200

1 00

o 40. 1 9 44.02 47.85 5 1 .67

Tex twist factor

Fig. 2-Variation in initial modulus (3%) with tex twist factor

rotor yarns, the maximum increase in modulus occurs at the lowest twist factor mainly due to the swelling shrinkage of fibres, which ultimately leads to im­proved packing. From the figures shown in the fore­going, it can be seen that there is a strong influence of two strain levels on initial modulus; the values ob­tained for 3% strain level are significantly lower. The structural deformation occurring at high strain level could explain this lower modulus.

3.2 Flexural Rigidity

Fig. 3 compares the flexural rigidity values of dif­ferent yarn structures before and after mercerization. Invariably, the mercerized yarns exhibit progressively higher flexural rigidity than the equivalent un mercer­ized yarns processed under identical conditions. The higher flexural rigidity is believed to result from the increased compactness of the structure, which restricts the freedom of fibre movement during bending. Fur­ther, the increase in flexural rigidity on mercerization is more marked in rotor-spun yarns. The magnitude of effect, however, depends on the yarn linear density, twist factor and rotor speed. As can be seen from Fig. 3, 17 .5% increase in flexural rigidity is observed for 29.5 tex rotor yarn spun at 833 .33 rps rotor speed with 40. 19 twist factor and it reduces to 15 . 1 % as the twist factor increases to 5 1 .67. Variation in rotor speed has

4 .,.----------------------------..,

3

2 �'e '" e.lJ .. '0 X t, 0 � 'Qj, . £: E 4 :::I :.0: ... C 3

2

o

� Kin' yarn (Or(')' 1 rn Rotor )'am, 110,\ .n fl1' (Grey) • RIJ4Of )lIn. l000 rp'(('rft)'.

40.19 44.02 47.85

Tex twist factor

Yarn h:.\, 29. 5

51.67

Fig. 3-Variation in flexural rigidity with tex twist factor

considerable effect on yarn rigidity. The increase in flexural rigidity on mercerization generally reduces with increasing rotor speed. Moreover, the increase in flexural rigidity also decreases when yarn linear den­sity is decreased from 59 tex to 29.5 tex.

3.3 Abrasion Resistance

The number of cycles required to rupture cotton ring- and rotor- spun yarns are given in Fig. 4. Gener­ally, rotor-spun yarns display lower abrasion resis­tance than their ring-spun counterparts. The experi­mental behaviour is caused by the quick rupture of surface fibres owing to high tension used during abra­sion testing, resulting in an early exposure of core fibres which lowers the abrasion resistance. On the other hand, the abrasion resistance of both types of yarns tends to decrease after mercerization. The analysis of variance demonstrates that the changes in abrasion resistance caused by mercerization are sig­nificantly influenced by the twist factor and rotor speed at a confidence level of 99%. This is particu­larly evident for the yarns produced with higher twist factor and rotor speed.

3.4 Packing Coefficient

Referring to Fig. 5, the difference in packing den­sities of ring- and rotor-spun yams results in different

"r1 !!'Q' UI I < �. � C· ::l ::l "0 � "'" 5' O<! � .., � C· ::l �. :r s >< � �. � n o .,

Packing fraction "r1 Abrasion resistance, cycles

a 9 '" a :". a 0 i:» 0 N f:::> f:::> • a> !!'Q' t

..... '" a 8 8 8 8 8 8 '" a a 0 0 0

;;: x � �. c:;> n o .,

.,.. 9 ...... co

t �

.,.. ..., a, (II

(II ..... i:» ...,

Yam Tex

-< II " � �

. 8 � ,. ,. ,. : I �. i 1 1 '- e � S/ ,_ ., � .... -i � � ;. " Cl -:. §

. ID � .. ,. .. a a :ii" � R .. � � � I I • .:J .:1 __ - .. >: � ; ! ! i a. f " -;; i � " ;. � ! !

.., :l. .., g . ::l ::l .., @ '" C· ::l ;; '" ;n' Er ::l n (11 �. :r s >< � �. iir' n o .,

;;: )( � �. j;> n o ..,

.,.. 9 ...... co

t o '"

.,.. ..., a, (II

� i:» ...,

Table 2-Influence of twist and mercerization of ring- and rotor-spun yams on hairiness Hairs/10m

Iinear twist Ring yam Rotor yam

w o a .,.. (11 o 0 o 0 . 8 � � � R st .. j 1 � � e � � ::: � � i �' '5 - � . ID � : : � R R .. 1 i 1 . e f § ... !I ! i [ f - -

l f - ! -< 3 n " � ;A

density factor Grey Men:erized 833.33' 1000' tex Imm 2mm 3mm >3mm Imm 2mm 3mm >3mm Grey Men:erized Grey Men:erized

Imm 2mm 3mm >3mm Imm 2mm 3mm >3mm Imm 2mm 3mm >3mm limn 2mm 3mm >3mm

29.5 40.19 1596 156 75 81 947 88

29.5 44.02 1372 92 56 .65 816 74

19

18

16

12

29.5 47.85 1270 48 40 45 773 41

29.5 51 .67 1 156 40 24 26 531 36

59.0 40. 19 2231 186 83

59.0 44.02 2139 175 60 59.0 47.85 2027 167 58

59.0 5 1.67 1743 158 55

'Rotor speed. rps

95 1686 174 41

72 1470 155 37

69 1265 143 20

66 860 120 15

22 20

18

13

719 1 1 8 21

681 78 15

578 36 I I

530 31 IO

46 990 141 45

42 861 136 43

22 840 128 20

16 680 1 10 16

23 680 39

16 653 34 12 548 30 10 469 24

47 884 72

44 810 68

22 726 59

20 608 48

17

I I

8

6

27

17

15

12

19 657 71

12 565 50

9 528 3 1

6 498 22

20

13

9

8

29 853 121 33

18 790 105 28

I7 723 !)of 19

13 606 82 15

22 649 37

14 . 624 3 1

10 517 29

9 448 22

34 780 61

30 712 56

20 686 52

17 582 45

10

8

7

5

13

II

IO

8

I I

9

7

6

14

12

12

10

0) o o

� » 9 I1l> til ::z: » :::0 3: � 3: tTl � !:2 N tTl o n § o Z :::0 Z o I1l> :::0 Q � til "tl � >< » � til

tv \0 Vol

294 INDIAN J. FIBRE TEXT. RES., SEPTEMBER 2005

diameters of these yarn structures. For both ring- and rotor- spun yarns, a decrease in packing coefficient is observed when these yarns are mercerized. The trend is consistent in all yarns, though the magnitudes of changes �e different between yarns. Decrease in packing coefficient of mercerized yarns agrees with the common view that the mercerization increases yarn diameter through swelling of the fibres within the yarn, which ultimately leads to increase in yarn diameter. Further, the yarns spun with different twist factors and rotor speeds respond differently to mer­cerization treatment. The packing coefficient of 29.5 tex mercerized rotor yarn ranges between 0.206 and 0.278 for 833 .33 rps rotor speed and between 0.2 1 9 and 0.306 for 1 000 rps rotor speed. I n the case of mercerized ring yarns, it ranges between 0.262 and 0.320 for 29.5 tex yarn and between 0.262 and 0.357 for 59 tex yarn. The diameter of mercerized ring and rotor yarns decreases with the increase in twist factor.

3.5 Hairiness

Table 2 shows the variation in hairiness of mercer­ized cotton yarns with twist factor and rotor speed. In general, rotor yarns are consistently less hairy than the equivalent ring yarns; the former contain fewer long and more short hairs. For both these yarns, there is a marked reduction in hairiness as the yarn linear den­sity decreases. For rotor-spun yarns, both short and long hairs markedly decrease as the rotor speed in­creases. A higher rotor speed leads to a reduction in friction force of the yarn in the section between the collecting groove and the exit that would retain a small number of hairs raised from the nucleus of yarn7• Change in twist factor also significantly re­duces both short and long hairs; a high twist factor is however preferable. Furthermore, regardless of proc­essing parameters used, the mercerized yarns have lesser hairiness than unmercerized yarns, as expected.

4 Conclusions

4.1 The flexural rigidity and initial modulus of cotton yarns at both 1 % and 3 % strain levels depend very much on yarn structure and twist factor used. Both these yarn characteristics, on the other hand, markedly increase on mercerization with sodium hy­droxide, irrespective of the yarn structure. The in­crease is reasonably more in rotor-spun yarns even at higher rotor speeds.

4.2 Rotor- spun yarns yield lower values of abra­sion resistance and packing coefficient than equiva­lent ring- spun yarns. The abrasion resistance of both types of yarns de�reases after mercerization but yarn twist increases it.

4.3 Cotton DE rotor- spun yarns exhibit fewer short and long hairs than ring-spun yarns, which decrease on mercerization. However, the yarn structural vari­ants considerably influence the reduction in both short and long hairs through mercerization.

References

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5 Barella A & Manich A M, cited in Blended Textiles, edited by M L Gulrajani [The Textile Association (India), Bombay], 198 1 , 250.

6 Dhanda K, Some studies on the properties of COttOIl ring­and rotor- spun mercerized yams, M Tech thesis, The Tech­nological Institute of Textiles & Sciences, Bhiwani, 2003.

7 Villa F, Pay A & Barella A, J Text Inst, 73 ( 1982) 55.