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 DOI: 10.1177/004051750407400709

2004 74: 607Textile Research JournalChing-Iuan Su, Meei-Chyi Maa and Hsiao-Ying Yang

Structure and Performance of Elastic Core-Spun Yarn  

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Structure and Performance of Elastic Core-Spun YarnCHING-IUAN SU, MEEI-CHYI MAA, AND HSIAO-YING YANG

Department of Polymer Engineering, National Taiwan University of Science and Technology,Taipei, Taiwan, Republic of China

ABSTRACT

In this experiment, we use a 44.4 dtex/4f spandex filament as the core and cotton fibersas the sheath to spin 19.7 tex elastic core-spun yarn. In order to improve yarn performance,we examine the yams cross-sectional structure and investigate the effect of draw ratio and feed-in angle of the spandex on the yarns’ structure and performance. The results showthat a higher feed-in angle provides a better cover effect and a draw ratio of 3.5 yieldsbetter dynamic elastic recovery.

Elastic core-spun yams use spandex as the core andare covered with natural fibers or other staple fibers.These yarns are then made into fabrics for various end-uses. Elastic core-spun yarns have important properties:they have the same feel as the shield fibers, and possessgood moisture absorption because natural fibers coverthe outer layer, they are comfortable to wear, and we canmodify their elasticity to fit different end-products. How-ever, natural fibers such as cotton, linen, silk, and wool,and man-made fibers such as polyester, nylon, and

acrylic do not possess any of the advantages of elasticcore-spun yarns. Therefore, elastic core-spun yarns canbe used to produce fabrics of varying styles, hands, andfunctions, and can be designed for woven and knittedfabrics according to their properties.

With the aim of enhancing good yarn performance,core yarns spun with spandex, man-made filaments, orstaple fibers have been the subject of considerable re-search [2, 1-8]. Babaarslan showed that core positioninghas a direct effect on the structure, properties, and per-formance of core-spun yarns [1]. Miao et al. concludedthat filament (core) tension during production has a

highly significant effect on sheath slipping resistance [2].Many others also contributed to this field. In this exper-iment, we employ an additional feed roller to deliver thespandex at draw ratios of 2.0-4.5. The spandex thenpassed through a V-grooved roller to stabilize its positionwhile it is fed onto the conventional ring spinning frame.To determine and improve the 19.7 tex elastic core-spunyarn qualities, we examine their cross-sectional struc-

tures and performance with respect to the draw ratio andthe feed-in angle of the spandex.

Experiments

The 0.417 g/m cotton roving was fed through the backroller of a modified ring spinning frame, and the 44.4dtex/4f spandex was positioned on an additional feedroller. The spandex was drawn at a ratio of 2.0-4.5 andpassed through a V-grooved roller with a contact angleof the front top roller (hereafter called the feed-in angle)shown in Figure 1. Finally, it was fed in with cottonfibers behind the front roller, thus spinning a 19.7 texelastic core-spun yarn. Figure 2 shows the load-elonga-tion curve of the 100% cotton yarn ( 19.7 tex), the span-dex (44.4 dtex/4f), and the elastic core-spun yarn ( 19.7tex).

FIGURE 1. Feed-in angle of spandex passed through a V-groovedroller with a contact angle of the front top roller.

In this experiment, we varied the draw ratio of span-dex from 2.0 to 4.5 (that is, 2.0, 2.5, 3.0, 3.5, 4.0, and 4.5)and passed it through a V-grooved roller with feed-inangles of 0°, 60°, and 120°. The spinning conditions

1 To whom correspondence should be addressed:cysu@tx.ntust.edu.tw

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FIGURE 2. Load-elongation curves of the 100% cotton yarn, thespandex, and the elastic core-spun yarn.

were 0.417 g/m cotton roving, 44.4 dtex/4f spandex,45/68 mm roller gauge, draw ratios of 2.0, 2.5, 3.0, 3.5,4.0, and 4.5, feed-in angles of 0°, 60°, and 120°, 10,000rpm spinning speed, and 19.7 tex yarn count. We definedthe count of the elastic core-spun yarn as follows:

COP = N + (S/Sd) (1)

where COP = count of elastic core-spun yarn (tex), N= count of the covered cotton (tex), S = count of the

spandex (tex), and Sd = draw ratio of the spandex.First, we examined 250 cross sections of the elastic

core-spun yarn by SEM, then classified them into fourrepresentative types according to the position of thespandex in the yarn as follows:

’

>

1. Center type: As shown in Figure 3a; the four dark-colored circles in the center the spandex, and theouter sheath is the cotton fibers. This is an ideal

cross-sectional structure for an elastic core-spun

yarn, where the spandex is positioned in the centerof yarn and its eccentricity is 0%.

2. Centers- ’/3R type: As shown in Figure 3b, thespandex is positioned between the center and ’/_3

radius of the yarn, and its eccentricity is 27.5%. ·3. ’/~R --- 2f3R type: As shown in Figure 3c, the spandex

is positioned between ’/3 radius and 2/3 radius of the

yarn, and its eccentricity is 33.0%.4. Radius type: As shown in Figure 3d, the spandex is

positioned beside the fringe of the yarn, and its

eccentricity is 47.6%.We studied the four kinds of cross-sections and

statistically analyzed the results of the experiment.Then we measured the stress and strain of the elastic

FIGURE 3. Cross sections of 19.7 tex elastic core-spun yam.

core-spuns yarn with a tensile tester to investigate theyarn properties of forty samples. Finally, to examinedimensional stability, especially in clothing, which isthe ability of a garment to keep its shape, we con-ducted a test of dynamic elastic recovery by experi-ence, as shown in Figure 4, where the line A-A’-A&dquo; isthe breaking load curve. We applied an imposed load(40% of the breaking load) to the 19.7 tex elastic

core-spun yarn and then released it, then applied thesame imposed load repeatedly. We then calculated thepercent elastic recovery of the yarn:

Results and Discussion

EFFECT OF SPANDEX FEED-IN ANGLE ON

CROSS-SECTIONAL STRUCTURE

The feed-in angle of the spandex influences stabilitywhen it is being fed into the spinning system and directlyaffects the spandex’s position in the cross section of theelastic core-spun yarn. In the experiment, we studied the

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FIGURE 4. Load-elongation curves for 19.7 tex elastic core-spun yam. under a repeated load of 40% of the breaking load.

yarn’s cross-sectional structure when spun with threespandex feed-in angles - 0°, 60°, and 120°.

Table I shows the effect of feed-in angle on the cross-. sectional structure of 19.7 tex elastic core-spun yarn: the

percentages of center type cross sections are 51, 63, and71 %, corresponding to feed-in angles of 0°, 60°, and120°. This can be explained by the fact that when thefeed-in angle increases, the oscillation of the spandexdecreases, resulting in a better covering effect duringyam spinning. Hence, the spandex tends to be positionedin the center, forming an elastic core-spun yarn withbetter performance.

TABLE I. Effect of feed-in angle on the cross-sectional structureof 19.7 tex elastic core-spun yarn.

As shown in Table I, except for the spandex positionedbeside the yam fringe (the radius type), the total values ofthe other three cross-sectional types (center type, center- 1/1R type, and 1/1R -... ¥1R type) are 98, 99, and 99%,corresponding to feed-in angles of 0°, 60°, and 120°. Thedata show that the V-grooved roller for spandex feed-in hasa better covering effect on the elastic core-spun yam.

EFFECT OF SPANDEX FEED-IN ANGLEON TENSILE PROPERTIES

Increasing the spandex feed-in angle (that is, increas-ing the contact angle of the spandex with the front toproller when it passes through the V-grooved roller intothe spinning system) is beneficial to spandex control, andmixing with cotton fibers will improve the elastic core-spun yarn performance. In this study, we examined theeffect on three feed-in angles (0°, 60° and 120°) on thetensile properties of the 19.’7 tex elastic core-spun yams.As illustrated in Table 11, when the spandex feed-in

angle increases from 0° to 120°, yarn stress and strainincrease to 20.2 cN/tex and 0.109 cN/tex, respectively. Inaddition, the CV% of yarn stress and strain decreases.This is because when spandex and cotton fibers are

mixed to form an elastic core-spun yarn, the spandex isfixed in a steady state and does not disturb the cottonfibers drafted in the nip of the front rollers. The yarn thusformed is smoother and more perfect. Consequently, thebreaking stress and strain of the yarn are improved, andthe CV% is also better.

TABLE 11. Effect of feed-in angle on mechanical propertiesof 19.7 tex elastic core-spun yarn.

EFFECT OF SPANDEX DRAW RATIOON ELASTIC RECOVERY

There is a gradual increase in permanent extension(decrease in elastic recovery) in successive cycles ofsimple extension cycling, and there is a correspondingincrease in total and permanent extension in load-cy-cling. These effects correspond to the same secondarycreep (nonrecoverable time-dependent extension) as thetest procedure 13]. Figure 5 illustrates the behavioralmodel of cumulative load-cycling. Here, we see thatelastic recovery decreases when the load-cycling numberincreases. This is because increased load cycling willcause the permanent extension to accumulate, thus re-

ducing the tendency toward elastic recovery. In addition.the elastic recovery increases when the draw ratio of the

spandex increases, especially at a draw ratio of 3.5. Thisis because the spandex will have greater stretch elasticitywhen its draw ratio increases; nevertheless, the elasticity

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FIGURE 5. Effect of spandex draw ratio on elastic recoveryof 19.7 tex elastic core-spun yam.

declines at a ratio of 4.0. This inverse can be imputed tothe speedy rise of the effect of secondary creep (nonre-coverable time-dependent extension). Consequently,elastic recovery declines after a ratio of 4.0.

Conclusions..

Passing the spandex through the V-grooved roller andkeeping a contact angle with the front top roller arebeneficial to the cover effect of the elastic core-spunyarn. Indeed, increasing the feed-in angle of spandex willdecrease its vibration. The additional V-grooved rolleremployed in this experiment helps position the spandexin the inner part of the core-spun yarn. In actual spinning,better tensile properties and elastic recovery of the 19.7tex elastic core-spun yarn can be obtained at a spandexdraw ratio of 3.5.

ACKNOWLEDGMENTS

This research was supported by the National ScienceCouncil (NSC91-2216-E-01 1-028). We are grateful toProfessor Tsang-Jou Yang of the Taiwan Cotton Spin-ners Association and our colleagues for their help withthe experiments.

Literature Cited

1. Babaarslan, Osman, Method of Producing a Polyester/Viscose Core-Spun Yam Containing Spandex Using aModified Ring Spinning Frame, Textile Res. J. 71(4), 367-371 (2001).

2. Miao, M., How, Y. L., and Ho, S. Y., Influence of SpinningParameters on Core Yam Sheath Slippage and Other Prop-erties, Textile Res. J. 66(11), 676-684 (1996).

3. Morton, W. E., and Hearle, M. A., "Physical Properties ofTextile Fibers," 2nd ed., Textile Institute and Butterworth& Co., 1975, pp. 322-340.

4. Radhakrishnaiah, P., and Tejatanalert, Sukasem, Handleand Comfort Properties of Woven Fabric Made from Ran-dom Blend Cotton-Covered/Polyester Yams, Textile Res.J. 63(10), 573-579 (1993).

5. Sawhney, A. P. S., Harper, R. J., Ruppenicker, G. F., andRobert, K. Q., Comparison of Greige Fabrics Made withCotton Covered Polyester Staple-Core Yarn and 100%Cotton Yam, Textile Res. J. 61(2), 71-74 (1991).

6. Sawhney, A. P. S., Ruppenicker, G. F., and Robert, K. Q.,Cotton-Covered Nylon-Core Yams and Greige Fabrics,Textile Res. J. 59(4), 185-190 (1989).

7. Sawhney, A. P. S., Kimmel, L. B., Ruppenicker, G. F., andThibodeaux, D. P., A Unique Polyester Staple-Core/Cot-ton-Wrap Yam Made on a Tandem Spinning System,Textile Res. J. 63(12), 764-769 (1993).

8. Sawhney, A. P. S., Robert, K. Q., Ruppenicker, G. F., andKimmel, L. B., Improved Method of Producing a Cotton-Covered Polyester Staple-Core Yam on a Ring SpinningFrame, Textile Res. J. 62(1), 21-25 (1992).

Manuscript received April /7. 2003. accepted August 25. 2003.

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