Indian Journal of Fibn: & Tex lile Research Vo l. 27, December 2002, pp. 362-368

Properties and processibility of compact yarns

.l yo li Rarjan Dash , S M Ishliaq ue & R Alagiru sa my"

Deparlmenl ofTexli le Techno logy, Incii anl nslilute o f Tec hnology. New Delhi 110016, India

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The e lTecl of winding speecl on :he propc rti'~s of ring and eompaci yarns produced using the same mi xing. preparatory process paramcters and spinning pa rametcrs h;ls becn studied. Bot h wct and dry splicing tcchniq ues were used during windin g to sludy Ihe sir-uel un: ,\Ild prope rti es o f the spli ced portions of the yarns. T he dyeing behaviour of ring and co mpact ya rns has al so bccn siudi ed to relate the structu re of these yarns 10 thei r dycability. It is observed that the co mpact ya rn exhibit s higher packing dcnsit y and tenaci lY hUI lowcr CV % or lhe tenacil y as compared to simil;!r ring yarn . The compaci yarn al so has lowc r number or lhi ck pl acl's. neps. short h;lirs and long hairs; the short and lor:g hairs howevcr inen:asc rapidly an cr winding and Ihe rat e or incrcasl: in hai riness is hi ghl: r lhan lhat in case o f ring ya rn. Al lhough the slrength or lhe spliced porti ons of cOlllpacl yarn is hi gher. Ihe rati o or splice sln: ngth to yrlrn slrength is lower. The fabri cs made with compact ya rns show hi gher KIS valucs than thc rab ri cs mack wilh ring y;lrIlS.

Keywords: Co mpact spinning. Ring :;pinning. Sp li cin g. Yarn h;li ri,less . Windin g speed

1 Jlltroductioll T he limitat ions of the ring spinning technology are

we ll known. One of the major limitations is the metal­to-meta l rubbing contact between the ring and th e travel ler, which restricts the spi ndle speed. The open­end rotor sp inni ng system was then deve loped to overcome the limitations of the rin g spinning system in respect of output rate. A nother important limi ta ti on of thc ring spinning technology is the formati on of spi nning tri an gle by the ri bbon of drafted fi bres emergi ng from the nip of the front drarting rollers.

A lthough ring-spun yarn is the measure of al l standards, it is never perfec t. If ring spun yarn is ~xa mined under the microscope, it is ea:;y to observe th;lt many f'ibres remain uncontrolled and arL; not bound into the yarn st ructure. T hese unbound f ibres, therefore, make no contribution to ya rn strength. In other words, if all the f ibres were equall y well i ntegratcd in the yarn , both strength and elongation could be increased. These protruding fibres are oftcn unfavourable in downstream processing as they ca u~e process ll1g problems and , therefore, make thc addi ti onal process stages ilecessary. Frolll 21 n ecologica l standpoint, thi s amou nts to deficient use of the raw material. The protruding f ibres must be re moved by si nge i ng as they are of no use. On the

" To whom all the correspondence shoul d be addressed. Phone: ()S9 141 9: Fax: 009 1-0 ! 1-658 1103; E-mail: rasamy61 @ilotmail.col1l

contrary, the volume of f ly in sp inning operations and in further processing is mainl y due to the protruding fibres or hairiness of the yarn . It can be dcduced from the abovc that the conventional ring-spun yarn certa inl y leavcs room for improvement.

In the preparati on of conventi onal ring yarn , the f;bres first enter the so-ca ll ed spi nning triangle illlmed iately after leav ing the front ro ller clamping line and then twisted together to form the fin ished yarn. The spinning tri angle has a dec isive inf: uence on ya rn sur face (hairiness), yarn strength , yarn elastic ity, running performance (end breaks), and fly li bcrati on (c leanliness) l.". Peripheral fibres are quite often not integrated in the yarn and are lost as f] y. Approx imately 85 % of th c fly in the spinning department ori ginates at the spinning tr ianglc. During twi st insert ion , the fibres are tensioned in longitud inal direction. Fibre tension reaches the max imum value at the outside of spi nning triangle and minimum at the center. Therefore, in the finished yarn the fibres have uncqual tension. When the yarn is subjected to tensile loads during further process ing or in the fini shed product, th e individual fibres with max imum pretension break first. Thi s means that the fibres forming the yarn body break one after the other and not simultaneously when subjected to load. Thi s ex plains why the total yarn strength is lower than the sum of indiv idual f ibre strength in the yarn cross­sect ion. To increase yarn strength, reducc yarn hairiness and f ly liberation , and to improve the

DASH et al.: PROPERTIES AND PROCESS IBILITY OF COMPACT YARNS 363

operating performance, it is decisive to eliminate the spinning triangle. For twi st insertion , the fibres shou ld be parallel, straightened and placed as close to each other as possible.

]n compact spi nning, the fibre stream coming out of the drafting unit is condensed by means of pneumatic compaction. As a result of thi s pneumatic compaction, the yarn hairiness is expected to reduce but the yarn strength and elongation are expected to increase. In the present work, an attempt has been made to compare the properties of compact yarn and correspondi ng ring yarn of the same count, spun from the same mixing. The packing coefficients, sp licing behaviour and influence of winding parameters on the properties of both the yarns have also been studied. The dyeing behaviour of both the yarns in terms of their packing coefficient is analyzed.

2 Materials and Methods 2.1 Materials

24s combed cotton ring and compact yarns were prepared and then used for the study. About 100 spind les were identified on a particular ring frame and full doff bobbins were then coll ected. To avoid variations, the same roving bobbins were used in compact spinning machine and a full doff was collected. The draft, spindle speed and TM were maintained at the same levels. The fibre specifi cations and spinning process parameters are given in Tables I and 2 respectively .

2.2 Winding All the samples prepared at ring frame stage were

wound on cones in wind ing machine (Schlafll orst Autoconer 338). Both ring and compact yarns were wound at three di fferent speeds ( 1000, 1200, 1400 mlmin) using both dry and wet spiicing. The same winding drum was used for both the yarns to minimize any variation. Baby cones weighing 125g were prepared. The yarn clearer sett ings were set at a re lative ly open configu ration so as to produce con tinuous length of yarn tor further testing. To study the splice strength, the sp li ced portions were co ll ected for both compact and ring yarns with dry and wet splicing. Spliced portions were collected before winding the yarn onto winding drum.

2.3 Dyeing of Fabric

The yarns were knitted on a plain knitt ing machine and the fabri c thus produced was then studied for the dyeing behaviour using rhe reactive dye. Both the fabrics were dyed in same dye bath under the ~ame

Table I- Fibre specifi cations

COllon

Upper half Illean length (UHM )

Micronaire

Strength

Short fibre index (SFI)

H4 ( 100%)

27 .43 111111

3.6

2.75 g/den

10.5

Table 2- Spinn ing process par:.lIncters

Process parameter Ring yarn Compact ya rn

Maehinc Ill Jke LG 5/ 1 Sussen

Spindle speed, rpm 16,500 16.500

TPI 16.3 16.3

Ring dia l11 eter. mm 45 45

Mass per bobbin. g 40-45 50-55

Suction pressure. 111 bar 35

dyeing condit ions. Six different shades were tried In both the cases .

2.4 Test Methods Yarn strength and elongat:on were measured using

Instron 430 1 tensile tester. Ten bobbins were co llected and 5 readings for each bobbi n were taken. To avoid the within-bobb in variations, readings were taken from the same position of cop. The gauge length was maintained at 50 cm. !n case of wound yarn , 50 readings were taken and th e gauge length was maintained at 50 cm. However, for testing the strength of spliced portions, the gauge length was maintained at 7 cm. The sp liced portions were posit ioned in the middle of the gauge length. Only those readings where the sp li ced porti ons (not the yarn) break first were taken.

Uster evenness tester was used to study U% and imperfections . Two read ings with a gap of 200 III at 400 m/min for I min w<:':-c taken 1'1'0 111 each cop and 10 such cops were tested for each type of yum. In case of the wound yarn, 20 readings per sample with the same gap were taken. Zweigle 535 was used for measuring the yarn hairiness. The speed was l11aintained at 50 m/min and the sal11ple length was taken as 200 m. The nUl11 ber of h~lirs for all the classes was observed. Aga in , the position of the cop was maintained at same level to avoid any within bobbin variation.

Projection microscope was used to measure the splice diameter. Yarn diameter was measured at Imm interva l over the whole spliced portion. The average Jnd standard devia tions in diameter with in the sp li ced port ion were calcu lLlteci . Thus, the average diameters of 5 spliced portions were measured and the standard

364 INDI AN J. FIRRE TEXT. RES., DECEMBER 2002

deviation between average spli ce diameters was observed. Moreover, to study the splice structure, scanning electron mi croscopy of the spliced portions was carried out and photographs were taken. Yarn di ameter measured under the microscope was taken as a basis for calcul ating the averagc ya rn packing density. Over 250 readings were taken on a projection mi croscope and the average diameter was calculated. The packing fracti on was ca lculated as the ratio of fibre specific volume to that of the ya rn .

3 Results and Discussion 3.1 Yarn Diameter and Packing Fraction

Tab le 3 shows the yarn di ameter and packing fraction at different winding speeds for both ring and compact yarns. In case of ring spinning, the width of the fibre ri bbon emerging out of the nip of the front ro llers is always greater under prac ti ca l conditi ons than the width of the spinning triangle and hence the spinning triangle can't catch al l the fibres fed in. This means th at many periphera l fibres are either lost or attached in a co mpl etely uncontrolled manner to the already twi sted yarn. In compact spinning, thi s scenario is changed due to the pneumatic compacti on of fibre stream. Due to the pos iti ve condensa ti on process the width of the fib re stream reduces. Thus, the fibre ribbon fed to the spinning triang le is very narrow, causing the spinning tri angle to virtually disappear. In thi s process, all fibres from the drafted ribbon are collected and fu ll y integratcd in the ya rn body. Due to the condensati on of fibre flow, all the fibres lie close to each other and due to the absence of spi nning tri angle, all the fibres are twisted to the ya rn body. Hence, the yarn produced becomes co mpact and the diameter of yarn remains lower th ::111 th at of the correspondi ng ring yarn . The pack ing fraction calculated from the yarn diameter is higher fo r compact yarn as compared to that for ring yarn .

Tahle 3-Yarn dia meters and packing fraction s

Yarn

Ri ng yarn

Co III pact yarn

Winding speed Ill/min

Un wound

1000

!200

1400

Unwound

1000

i200

1400

Yarn diameter

mill

0. 185

0.1 89

0.192

0. 190

0. 174

0. 170

0. 168

0. 172

Standard Packing deviati on of fracti on

yarn diameter

3.08 0.582

2.67 0.576

2.4 1 0.56 1

2.4 1 0.532

2.05 0.683

2.4 1 0.7 12

2.42 0.732

2.53 0.694

It is observed from Table 3 that the packing fraction of ring yarn decreases after winding; the decrease is however pronounced at higher winding speed (1400 m/min). On the other hand, a reverse trend is observed in case of compact ya rn . Up to wind ing speed of 1200 m/min , the pack ing frac tion of compact y<1 rn increases and at 1400 m/min winding speed, the pack ing fraction decreases ; the value is however still higher than that of ori ginal yarn (unwound).

During winding, pronounced abrasion takes pl ace on the surface of the ring yarn. The hooks, loops and long hairs present in ring yarn come in contact with va ri ous ya rn guides and winding drum. With high winding speed and hence with high winding tension , shear force is exerted 011 lhese fibres (hooks, loops and long hairs). In due course, these surface fibres exert tension on subseq uent fibres embedded on ya rn body , pulling them to the surface and mai-:ing the yarn structure loose. The same phenomenoll is repeated with hi gher winding speed much profusely and more loosening of yarn structure is observed. Thus, the diameter of yarn increases anci the packing fract ion ca lculated from it decreases .

In compact spinning, due to the pneumatic compaction and absence of spinning triangle, the hooks and loops are not found. The structure becomes smoother and more compact, and hence the compact yarn passes through various yarn guides smoothl y. The fibres in the yam body take up the high winding tension and further strai ghtening occu rs. Therefore, the fibres lie more close to each other, the diameter decreases and the packing fraction increases. At a wind ing speed of 1200 m/min , the max imum packing fracti on is obtained. The packing fract ion, however, decre,!ses at a hi gher winding speed of 1400 m/min. At hi gher winding speed, there is a cons iderable abras ion on fibres which causes damage to ya rn surface. This, in turn , leads to the formation of protruding ends which increase the diameter and hence decrease the packing density.

3.2 Yarn Strength and Elongation

The tensile properti es of ring and compact yarns are shown ill Table 4. It can be observeJ from the tab le that the tenacity of compact yarn is hi gher than that of the corresponding ring yarn by about 10%, which is a signifi cant difference since the sa me materials and process parameters were used in both the cases. The CV% of tenacity is higher in case of ring yarn . Thus, it is clear that the compact yarn is

DASH el uf.: PROPERTIES AND PROCESSlBlLITY OF COMPACT YARNS 365

stronger and more uniform than the corresponding ring yarn. This also confirms the findings of Artzt J

and Olbrioh4.

In compact spinning, the fibres li e close to each other and the spinning triangle is not found. Almost all the fibres are embedded in the yarn body and more number of fibres contribute to yarn strength . Due to the pneumatic compaction, the fibres li e close to each other and cohesion between the fibres is increased. All these factors contribute to yarn strength and hence the tenacity of compact ya rn is higher than that of the corresponding ring yarn. In case of elongati on-at­break, the compact ya rn shows a lower va lue before winding as compared to the ring yarn but the difference is not found to be signifi cant.

In case of ring yarn, the yarn strength continuousl y decreases with the increase in winding speed. The CV% of tenacity of ring yarn abo decreases with increase in winding speed. However, an altogether different trend is observed in case of compact yarn . Up to a winding speed of 1200 m/min , the strength of compact yarn increases and with the rurther increase in winding speed to 1400 m/min , the yarn tenacity shows a downward trend. The CV% of ya rn tenacity

Table 4- M echanical propcrti es of ring and compact yarns

Yarn Winding Tenacit y Elongat ion-speed cNllex at-break

m/min %

Unwound 15.52 (7. 10) 6.81 (525)

1000 15.98 (5.41 ) 6.53 (5.46) Compact yarn 1200 16.76 (5.36) 6.24 (5 .22)

1400 15.1 7(6.59) 6.09 ((S1 )

Unwound 14.31 (7.39) 6.89 (5.07)

Ri ng yarn 1000 13.85 (6.26) 5.67 (6.7 1)

1200 13.60 (5.68) 5.4 1 (6.82)

1400 13.25 (5 .24) 5. 13(7. 17)

The values within parenthcses indicate CV%.

al so follows the same trend. Up to winding speed of 1200 m/min, the CV O/O of yarn tenacity decreases and with the further increase in winding speed tol 400 m/min it increases. The elongati on-at-break decreases with the increase in winding speed for both the samples. Although the CV % of elongation-at-break of the compact ya rn follow s no trend, it increases with winding speed in case of ring yarn.

With hi gher winding speed , more loosening of yarn takes place in case of ring yarn and this is the main reason why yarn strength decreases with the increase in winding speed. In case of compact yarn . thi s process does not happen, instead furth er fibre straightening takes place as exp lained earli er. At a winding speed of 1200 m/min , maximum strength is obtained and with the further increase in winding speed, the strength decreases due to the damage of yarn caused by abrasion.

3.3 Yarn Imperfections

It is observed from Table 5 that there is no tTend in the number of thin places at all the sensitivity levels. The thick places/lOOOm are slightly hi gher in case of ring yarn ; the difference is however not significant. The difference in case of neps is also not significant. As the winding speed is increased, the thick places are reduced in compact spinning but in case of ring yarn no trend is observed and it is almost equal to the original value. At +200% level, the neps increase at a constant rate in case of ring ya rn but in case of compact yarn no trend is observed. However, at + 140% level, there is a significant increase in the neps level fo r the compact ya rns also. As already discussed , the fibres in compact yarn take up the winding tension. and fibre strai ghtening occurs, causing reducti on in number of thick places. In case of ring yarn, the increase in neps with the increase in winding speed can be attributed to the high hairiness

Table 5- lmperfecti ons of ring and compact ya rns

Winding U% Imperrect ions/ 1000m speed Neps Thin ~I aces Thick ~I aces

Yarn

m/min +140% +200% -30% -40% -50% +35% +50% +70%

Unwou nd 8.87 14.23 10. 13 1.26 0.28 0 15.86 11 .88 10.28

1000 8.82 15. 16 10.50 1.34 0.19 0 15.78 9.65 10.22 Ring yarn

1200 9.08 15.23 10.83 1.20 0 0 13.46 14.50 9.45

1400 9.08 16.50 I 1.5 1.36 02 1 0 14.45 11.00 9.60

Unwound 8.67 14.23 10. 11 1.32 0.22 0 13.22 9.25 8.88 Compact yarn 1000 8.59 15. 16 10.50 1.28 0.24 0 13.01 8.1 5 7.92

1200 8.46 16.03 12.50 1.44 0.24 0 12.55 7.50 7.90

1400 8.56 16.20 10.50 1.56 0. 15 0 12 .04 6.32 7.2 1

366 IND IAN J. FII3RE TEXT. RES .. DECEMB ER 2002

of the unwound yarn . The long hairs which are present in unwound ring yarn roll themse lves into neps due to their rubbing action against the yarn guides during winding operati on. Similar mechani sm works in the compact yarns, leading to increase in the smaller size neps.

3.4 Yarn Hairiness

The hairiness test results are shown in Table 6 and Figs . I and 2. It can be observed from Fig .1 that the short hairs (up to 2mm length) are nearly half in case of compact yarn as compared to that in case of ring yarn. However, more interes ting results (Fig.2) are observed in case of long hairs (>3 mm length). The number of long hairs in compact ya rn after winding increases around ten times of its original va lue. The total number of hairs (both long and short) in case of compact ya rn is found to be hal f of that present in case of ring yarn.

Accord ing to Hechtl 5, the hairiness is hi ghly

reduced ( 13 % on an average, 3-27%depend ing on the material and yarn) in compact spinning due to the better fibre in volvement in yarn formation. In ring spinning, by over twi sting of the outer fibres in the spinning triangle, some percentage of fibres break. This phenomenon does not occur in compact spinning. Due to the pos itive condensation, the width of the fibre stream red uces after drafting and almost all the fibres are incorporated into the ya rn body. This is the main reason why the number of long hairs is lesser in compact yarn t~an that in ring yarn.

It is observed that after winding the hairiness level in yarn increases. Howeve r, the per cent increase is the one which matters the most. Table 6 shows that at a winding speed of 1000 m/min , the increase in long and short hairs is found to be 144% and 11 8% respectively in case of ring yam. In case of compact yarn, the per cent increase in number of long and short hairs is found to be hi gher than that in ring yarn .

However, the number of hai rs is lesser ill compact yarn than that in corresponding ring yarn. In case of compact yarn , the short hairs increase to three times of its original value. The per cent increase in long hairs is found to be around 800%. After wi nding at a speed of 1200 m/min, the per cent increase in short and long hairs is found to be 134% and 171 %

70 .~

0

x 60 E

0 0 50 N

.::: en

40 ... ] (; 30 ,<: Vl

'-

--Ring

--Compact 0 0 20

%

10 600 800 1000 1200 1400 1600

Winding Speed (rpm)

Fig. I- Effect of wi nding speed on number of short hairs

40~-----------------------------,

~ -+-King 0

x ~ 30 --Compact

0 0 <'1

::: Vl 20

. !oJ

'" .!:: 01)

~ 0

...J \0 ..... 0 0 z

O +-----~----_r----~----~----~ 600 800 1000 1200 1400 1600

Winding Speed (rpm)

Fig.2- EITect of wi nding speed on number o f long hairs

Table 6- I-iOJiriness of ring and compact yarns

Yarn Winding speed Short hairs Long hairs Increase in Increase in Ill/min short hai rs, % long ha irs. %

Unwound 27.976 1057

Ring ya rn 1000 60.94 1 2585 11 8 144

1200 65 ,53 1 287 1 1:\4 17 1

1400 43 ,545 1637 55 54

Unwou nd 15,367 134

Com pact ya rn 1000 45.114 1230 193 S IS

1200 50,679 1375 229 926

1400 46,618 87 1 203 550

DASH el al. : PROPERTI ES AND PROCESSIBILITY OF COMPACT YARNS 367

respectively in the case of ring yarn. In case of compact yarn , the per cent increase in short hairs is 229% and in long hairs , 926%. Though the per cent increase is higher in case of compact yarn, sti ll the short hairs, long hairs and total hairs are lesser than those in case of the corresponding ring yarn.

At a winding speed of 1400 m/min. the number of hairs increases over the original unwound yarn in both the cases; however, the per cent increase is lower than that at a speed of 1200 m/m in. The number of hairs (long, short and both) is lesser at 1400 m/m in in both the cases.

In case of ring yarn , there are hooks and loops, and therefore due to the rough yarn surface structure the hi gh abrasion takes place whil e the ya rn passes through various ya rn guides during winding. This leads to the increase in hairiness after winding. However, the winding tension is hi gh at a winding speed of 1400 m/m in . Due to the hi gh shear force exerted on the ya rn when it passes through various yarn guides, the long hairs break and the va lue is lesser than that wound at 1200 Ill/min. In compact spinning, due to the positi ve condensation the fibre ends are embedded in the yarn body . So, the fibres which are embedded in the ya rn during yarn fo rmat ion take up the hi gh winding tension and tend to protrude ou t or ya rn body wh il e passing around various yarn guides, thus increas ing the hairiness. Thi s is the mai n reason why the per cent increase is more in case of compact ya rn . However, after 1400 m/m in winding speed the long hairs break due to the hi gh shea r force through various ya rn guides, as explained in case of ring yarn .

3.5 Analysis of Spliced Portions

The splicing behaviour of rin g and compact ya rns is shown in Table 7. For both ring and compact ya rns, the spliced porti ons produced by wet spli cing show a higher breakin g load than that produced by dry splicing. The breaking loads of spliced portions of compact yarn produced by both wet and dry splicing are higher than those of the corresponding spliced portions of ring yarn. However, the splice/yarn strength rati o of compact yarn is lower than that of ring yarn for both wet and dry sp li cing. In both dry and wet spli cing, CV O/O of breaking load of nng spliced portions is lower than that of the corresponding spliced portions of compact yarn.

It is observed from Table 7 that the spliced porti ons of ring yarn show higher breakin g elongation than the corresponding spli ced portions of compact yarn. In

Table 7-Propenies of spliced port ions of ring and comp~c t yarns

Propert y Wet spli c ing Dry splic ing

Ring Compact Ring Compacl yarn yarn ya rn yarn

Av. diaIll . of splice. I11Ill 022 0.22 0 .24 0.: 3

Splice/yarn di~m. rat io 1.24 1.30 125 1.35

SD o f spli ce diam .. mm 0. 342 0 .996 0 .856 1.20

Break ing I ()~d. g 30 1.6 3 12.9 2TU 281.6

Splice/yarn strengt h ratio 0. 84 0.80 0 .76 0.72

C V% o f break ing load 11 .2 15.4 11.2 139

Tenac it y, eN/lex 9.95 12.46 10.70 11.20

Elongalion-a t-break. % 5.9 5.6 8.7 8.1

Spli ce/yarn c l nng~tion 0 .92 0.89 1.37 1.29 rati o

CV % of e longa tion- 11 .5 :\.3.0 22.3 43:\ at -break

Fig 3- Scanning e lec tro n mi crograph or sp liced portions of ri ng y (~rn

general , the elongati on-at-break of spli ced portions made by dry splicing is hi gher than that of wet splicing porti ons in both ring and compact yarns. Allhough there is no significant di ffe rence in the diameters of ring and compact yarns, the increase in diameter with respect to ori ginal yarn diameter is lesser in case of ring yarn than that in case of compact yarn . In case of compact ya rn , the fibres are more closely bound and therefore leave no proper opening during splicing. This is the main reason why the spliced portions of com pact yarn show a lesser percentage of original yarn strength than the corresponding spli ced portions of ring yarn . Figs 3 and 4 show that in spliced portions of compact yarn ,

368 IN DIAN J. PIBRE TEXT. RES .. DECEMBER 2002

Fig 4--Scanning electron micrograph of spliced portions o r compac t yam

Tahle 8- KIS va lues o r ring and compact ya rn fabrics

% shade Ring sample Compact sample

I 6.90 7. 18

2 8.70 9.2 1

3 12.40 13.53

4 13.40 14. 10

5 15.30 15 .90

6 26. 10 26.90

there is no proper opening and the fibres are wrapped up against each other. The trends in elongation and average diamete r also support the above argument.

3.6 Dyeing Behaviour of Ring and Compact Yarns

Table 8 shows the KIS values of knitted fabrics prepared from ring and compact yarns. The fabrics made from compact yarn show higher KlS values than the fabrics made from ring yarn at different shades. As the ha iriness of compact yarn is lower than that of the corresponding ring yarn, the fabrics made from compact yarn are lustrous and brighte r. As the yarn structure is compact in case of compact yarn , less dye penetrates to the yarn core. Dyeing rakes place mostly

on the surface fibres. That is why the shade of the fabric made from compact yarn is brighter. Therefore, in case o f compact yarn , o ne can use less percentage of dye for the same level of shade. Thi s a lso he lps in savings of dyes and chemi cals.

4 Conclusions As compared to ring yarn, the compact yarn has

lower diameter and higher packing fraction. The pack ing fract io n of compac t ya rn first increases w ith the inc rease in winding speed and then decreases at hi gher speeds. The tenac ity o f compact ya rn is around 10% hi gher than that of the corresponding ring yarn but its C V% is lower, suggesting a more uniform yarn in case o f co mpact spinning. In case o f compact yarn , the ten ac ity first inc reases and then decreases with increase in winding speed. For the compact yarn , the number of thi ck places decreases but U% and neps do not show any trend with the inc rease in winding speed . The number of short and lo ng hairs is sig nifi cantl y less in the case of compact yarn. With the increase in winding speed, the short and long hairs inc rease in both ring and compact yarns but the per cent inc rease is more in case of compact yarn, particularly the long hairs inc rease at a faste r rate. A lthough the strength of spli ced po rtions of compact yarn is hi gher, the rati o of splice <; trcngth to yarn strength is lower due to the improper opening of yarn. The dye does not penetrate into the yarn core in case of compact yarn and is deposited on the surface, the reby showing a bri ghter shade.

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March (2000) 26. 2 Fuestel M, Deve lopment of new yarn based on compact spin­

ning techno logy , Me//iond 1111 . 5, November ( 1999) 273. 3 Art!.t P, The spec ial st ructure of compact yarn- advan tages in

down stream processing , 1111 Texl Bul.! Yom alld Fabric FOnll ­illg, (2) ( 1997) 4 1.

4 Olbrioh A. The Air Com Tex 700 conden~cr ring spinning mac hine, M e/lialld 1111 .6, March (2000) 25.

5 Hecht l R, Compact spinning system- an opportunity ror im­proving the ring spinning process, Me/liand Texlilber. (4)

( 1996) E 37.