characteristics of imperfections in cotton and blend...

Indian Journal of Textile ResearchVol. 13, December 1988, Pp. 192-197

Characteristics of Imperfections in Cotton and Blend Yarns

AAGUPTE

Textile Department, Victoria Jubilee Technical Institute, Matunga, Bombay 400 019, India

andN BALASUBRAMANlAN

The Bombay Textile Research Association, L B S Marg, Ghatkopar (West), Bombay 400 086, India

Received 23 May 1988; revised and accepted 29 September 1988

Different yam properties like diameter, hairiness, weight per unit length, turns/em, fibre length, breakingstrength and elongation have been studied at the thin and thick places and compared with that found in the nor-mal portion of cotton and polyester/cotton yams to get a better understanding of the contribution of imperfec-tions to yam quality. The actual diameter of thin place agrees with the calculated diameter but the actual diameterof thick place is much higher than the calculated diameter. The tenacity of thin places is lower compared to thatof normal portion. the effect being more prominent in polyester/cotton blend yam. Thick place, however, hasnearly the same tenacity as the normal portion.

Keywords :Breaking strength, Cotton yam, Elongation, Imperfections, Polyester/cotton yam, Yam hairiness

1 IntroductionImperfections in yarn not only influence the ap-

pearance of yarn and fabric but also the perform-ance of yarn in weaving. The causes of higher le-vels of thin and thick places in yarn may be foundeither in the raw material or in imperfect prepara-tion processes'. Although a number of studies"?have helped in understanding the process parame-ters affecting the level of thin and thick places inthe yarn, the general level of imperfections in In-dian yarns is many times higher than internationalnorms and is one of the reasons for our relativelypoor share in the export market. Gupta and Vi-jayshanker'' have shown that small fragments ofseed-coats present in the sliver, as a result of un-satisfactory ginning, result in blemishes like neps,thick places and classimat A and B faults in theyarn. In medium count yarns, there is a well-de-fined quantitative relationship between the fre-quency of blemishes in yarn and the percentageseed-coat content in the sliver used to spin theyarn. Further, Gupta et al.9 have shown that mostof the blemishes in fine count yarns originatefrom the short and immature fibre bunches thatare generated during ginning from the immatureseeds and ovules present in the seed cotton itselfand concerted efforts would have to be made toovercome the problem of occurrence of excessiveimmature seeds and ovules in our cottons. Whileanalyzing yarn imperfections, Balasubramanian et

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al." found lack of agreement between mass anddiameter of imperfections, suggesting that thestructure and composition of the imperfectionscould also vary. The thin places were totally freefrom foreign matter and immature ovules, whilefibre cluster and foreign matter contributed 60-90% of thick places. Immature ovules and foreignmatter contributed to about 75% of the totalnumber of neps.

A critical study of the physical properties ofyarn at thin and thick places will provide a clue totheir formation. The way in which the yarn pro-perties are modified at these places compared tothat found in normal portion will facilitate a bet-ter understanding of the contribution of imperfec-tions towards yarn quality. Therefore, in the pres-ent study, different yarn properties like diameter,hairiness, weight per unit length, turns/em, break-ing strength and elongation have been studied atthe thin and thick places and compared with thatfound in the normal portion of yarn.

2 Materials and MethodsDifferent combed cotton yarn samples and pol-

yester/cotton blended yarn samples collectedfrom the mills were used (Table 1).

Samples were run through Uster evenness tes-ter and with the help of yarn imperfection selec-tor 50 thin places (at - 50% sensitivity) and 50

GUPTE and BALASUBRAMANIAN: CHARACTERISTICS OF IMPERFECTIONS IN YARNS

Table 1- Mixing and Blend Percentage of Yam SamplesYarn Count Mix Cotton Percentage Composition of blend

Tex (Ne)

15 Combed (40) A DCH32 83MCU5 17

10 Combed 1(0) A DCH32 83MCU5 17

6 Combed (1001 B Suvin 83DCH32 17

15P/C (40) Blend C Polyester 45 Terene 1.5 d, 45 mmCotton 55 Cotton Mix.A

12 PIC (50) BlendD Polyester 67 Terene l.2 d, 38 mmCotton 33 Cotton Mix. A

10 PIC HT (60) Blend D Polyester 67 Terene l.2 d, 38 mmCotton 33 Cotton Mix. A

PiC - Polyester/Cotton; and HT - High twisted.

thick places (at 3 sensitivity, i.e. + 50%) were col-lected. Without allowing the twist to be lost eachsample was fixed with cellotape on a paper framehaving window size of 1 cm x 7.5 cm. While fixingthe sample on paper frame, thin place/thick placein the yam was kept in the central position of 7.5ern yam length mounted on the paper frame.Then 50 samples were prepared by taking normalyam portions which is a randomly selected por-tion from the bobbins (5 specimens were takenfrom each of ten bobbins every time).

The samples were tested on Projectina for yamdiameter, hairiness and then on Instron for singlethread strength and elongation percentage of thinplaces, thick places and normal portions of yam.Yam hairiness was measured by the method ofSubramanian et al," which is a modification of Je-dryka's method'<. For single thread strength, yamsamples from paper frame were mounted betweentwo jaws of Instron at a gauge length of 7.5 emand the paper frame was cut before testing. Afterthe test, the broken specimen was cut close to thejaw and weighed for yam count and tenacity de-termination. The count was based on 7.5 emlength of yarn in these tests.

For determining the weight per unit length ofnormal, thin and thick places, the yarn was putunder a tension of tex/2 and a length of 1 em wascut and weighed. For thin and thick places the re-spective fault length of 1 cm was cut and weighed.Table 3 shows the actual weight per unit length ofthin and thick places. It is pertinent to mentionhere that the values of yarn count given inTable 7 are based on the weight of 7.5 em length,which includes a thin or thick place. Therefore,there is some difference between the two weights,the weight of thin places in Table 3 being lower

than that in Table 7 and the weight of thick placesin Table 3 being higher than that in Table 7.

Further, 20 samples each of normal, thin andthick places were tested for twist per unit lengthon twist tester with a gauge length of half an inch.Fibre length was also measured at these places.For this purpose, thin and thick places were col-lected, untwisted and fibres from the respectiveportions were tested for fibre length. Each fibrewas straightened on a glass plate with the help ofa few drops of paraffin oil smeared on the plate.The length of each individual fibre was measuredwith a scale in mm. Five hundred fibres weremeasured for each sample.

3 Results and Discussion

3.1 Yam DiameterTable 2 shows average yarn diameter at normal,

thin and thick places of yarn. It is seen that thediameter of thin places is around 70% of the nor-mal yarn diameter and there is not much variationbetween the samples. The diameter of thickplaces is more than 150% of the normal yam di-ameter and there is variation between the sam-ples.

A thin place recorded with sensitivity - 50%on Uster indicates the presence of yam mass lessthan 50% of the average value which is propor-tional to (tex/Z). Since the yarn diameter is pro-portional to ~ the thin place will have a diameterproportional to ]tex/2 or (0.707) (v~). The diame-ter of thin place will be therefore (0.707) times nor-mal yarn diameter.

On the same basis, sensitivity position 3(i.e. + 50%) for thick places will indicate presenceof yam mass 1.5 times its average value which is

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INDIAN J. TEXT. RES., VOL. 13, DECEMBER 1988

Table 2- Yam Diameter (Actual and Calculated) at Normal, Thin and Thick Places

Actual yam diam (rom) Calculated yam diam (rom) Actualdiamx 100

Normal Thin Thick Thin Thick Calculated diamportion place place place place

Thin Thickplace place

0.1499 0.1040 0.2360 0.106 0.184 98.11 128.54(69.38) (157.44)

0.1289 0.0910 0.2760 0.092 0.159 98.91 173.58(70.67) (214.12)

0.0942 0.0627 0.\732 0.067 0.115 94.14 150.61(66.56) (183.86)

0.1491 0.1006 0.2293 0.106 0.184 94.91 124.62(67.47) (153.79)

0.1235 0.0891 0.2186 0.087 0.151 102.41 144.77(72.15) (177.00)

0.1062 0.0757 0.2229 0.075 0.131 100.93 171.46(71.28) (209.89)

Sample

15 Combed

10 Combed

6 Combed

15 PIC

12P/C

lOP/CHT

P/C- Polyester/cotton; and HT - High twisted.Values in parentheses indicate percentage with respect to normal.

equivalent to a yam diameter (1.225) times nor-mal yam diameter.

The yam diameter values for thin and thickplaces were calculated from the actual diameter ofnormal portion using the above relationships andthe results are given in Table 2. It is seen that theactual diameter values of thin places agree verywell with the calculated values. But the actual di-ameter values of thick places are much higherthan the calculated values. This may be partly be-cause thick portions are undertwisted and are,therefore, more bulky in relation to normal por-tions and the influence of twist on diameter ismore at lower levels of twist than at higher levels.The reduction in diameter with increase in twist ismore prominent at low twists and it decreasesprogressively with increase in twist.3.2 Weight per Unit Length

The actual weight per unit length of the yam atthin and thick places was compared with that ofthe normal portion of yam. Table 3 shows thatthe weight per centimeter of thin places is 60%and that of thick places is around 150% of thenormal portion. Since thin places should includeonly those portions whose weight is less than 50%of the average, the sensitivity level in actual prac-tice is different from that indicated in the instru-ment. Portions up to or even above 60% of thenormal seem to get counted as thin place.

3.3 Turns/emTurns/ cm in normal, thin and thick places are

given in Table 4. It is seen that turnslcm at thin

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Table 3-Weight per Unit Length of Yam at Normal,Thin and Thick Places

Sample Actual wt/cm (l1g)

Normal portion Thin place Thick place15 Combed 164.78 101.90 249.04

(61.84) (151.13)10 Combed 99.04 63.36 155.80

(63.97) (157.31 )6 Combed 59.26 35.00 87.00

(59.02) (146.71)15 PIC 149.84 93.34 216.70

(62.28) (144.66)12 PIC 112.90 69.30 174.20

(61.38) (154.33)lOP/CHT 99.24 60.03 141.50

(60.76) (142.58)

Values in parentheses indicate percentage with respect tonormal.

places are 150% and at thick places 70% of thoseat normal portions of yam. It is, therefore, ob-served that thin places, which have generally 60%of the normal yam weight, are overtwisted to theextent of 150% of the normal yam twist. Similar-ly, thick places, which have 150% of the normalyam weight, get lower twist to the extent of 70%of the normal yam twist.3.4 Yarn Hairiness

Table 5 shows that the yam hairiness at thinplaces is about 35% and at thick places above150% of the normal yam hairiness. For 10 PICyam, which is high-twisted, the hairiness is com-paratively lower. The thick places which have

GUPTE and BALASUBRAMANIAN: CHARACfERISTICS OF IMPERFECfIONS IN YARNS

more than 150% normal yam diameter andweight per unit length are expected to have morehairiness in yam as the number of fibres in across-section is likely to be more. Moreover,these places are soft twisted which would also re-sult in more hairiness. Thus, the increase in incid-ence of thick and thin places will lead to morevariability in hairiness.

3.5 Fibre LengthTable 6 shows that mean length and length

CV/o for different samples do not differ much forthin and thick places of yam. For 15 and 10combed samples, the fibres shorter than 16 mmare more at thick places than at thin places ofyarn. For 6 combed sample, there is no differencein the percentage number of fibres shorter than16 mm at thin and thick places.

The other workers have found more short fi-bres at thick places than at thin places of yarn".All the samples used in this study were combedand, therefore, the percentage short fibres is low-er compared to that for carded samples and thismay be one of the reasons why not much differ-ence in short fibre content is seen between thickand thin places in the present study.

3.6 Yarn StrengthSingle thread strength and elongation-at-break

for normal, thin and thick places are given inTable 7. The table also gives the tenacity (g/tex]values calculated from the tex values of the testedsamples. As expected, the breaking strengths ofthin places are lower and those of thick placeshigher than the breaking strengths of normal por-tions. When the strength is corrected for weightper unit length, the thin places are found to beweaker compared to the normal portions in 5 outof 6 cases. The thin places in polyester/cottonblend counts 12 and 10 in particular have a muchlower tenacity than that of the normal portion.This means that some disturbance in the spinningprocess has resulted in the formation of a thinplace and hence the intrinsic strength or tenacityis reduced. The thick places, however, have nearlythe same tenacity as of the normal portion exceptin 6 combed and 12 PIC where the tenacity ofthick place is lower.

Elongation % of thick places is higher than thatof normal portion in cotton yam. This is, how-ever, not true for polyester/cotton blended yarn.

Elongation % for thin places is lower than thatof normal portion, the difference being very

Table 4- Twist Level in Normal, Thin and Thick Places Table 5- Yam Hairiness in Normal, Thin and Thick

Sample Turnslem Places

Sample Hairiness (mm)/10 emNormal portion Thin place Thick place

15 Combed 9.80 14.45 6.77 Normal portion Thin place Thick place

(147.4) (69.1) 15 Combed 45.86 19.11 61.3710 Combed 14.70 22.44 10.00 (41.67) (133.80)

(158.4) (70.6) 10 Combed 39.25 14.11 83.356 Combed 18.66 29.53 12.01 (35.95) (212.36)

(158.3) (64.4) 6 Combed 32.34 13.89 52.2615 PIC 11.34 16.26 9.06 (42.95) (161.60)

(143.4) (79.9) 15 PIC 35.80 11.03 61.4512 PIC 12.87 18.50 8.86 (30.81) (171.65)

(143.7) (68.8) 12 PIC 27.34 9.26 60.1910 PIC HT 17.60 28.39 15.67 (33.69) (220.15)

(161.3) (69.0) 10 PIC HT 27.93 8.53 41.31(30.54) (147.91)



Table 6-Fibre Length at Thin and Thick Places

Sample Thin places

Mean Length Fibres Meanlength CV% <16mm length

0/0

15 Combed 30.28 24.26 5.2 31.4210 Combed 28.95 24.79 3.8 27.466 Combed 30.66 24.40 3.6 31.40

Thick places

LengthCV/o

Fibres<16mm

0/0

25.3726.9822.29

7.610.23.4

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INDIAN 1. TEXT. RES., VOL. 13, DECEMBER 1988

Table 7 -Single Thread Strength and Elongation % in Normal, Thin and Thick Places

Yarn count Breaking load Tenacity Elongation

tex CV'/o

15 CombedNormal portion 15.90 12.18Thin place 12.03 8.54Thick place 18.61 11.51



15 PICNormal portion 14.66 10.22Thin place 10.87 10.10Thick place 16.38 10.25

12 PICNormal portion 10.78 12.81Thin place 8.84 11.54Thick place 13.87 10.30

10 PICHTNormal portion 10.04 14.45Thin place 7.70 11.71Thick place 10.81 10.29

g CV'/o g!tex CV'/o E% CV'/o

288.24 16.66 18.07 8.49 7.53 11.04233.12 10.17 19.42 9.05 7.19 12.09332.40 14.76 17.85 8.49 8.30 9.65

185.06 14.80 18.48 7.69 8.08 to.78145.00 14.03 16.96 9.63 7.82 11.15228.04 16.01 17.96 9.48 8.99 to.33

114.60 19.19 20.11 13.56 6.21 14.6281.64 12.44 17.90 13.09 6.15 12.78124.22 17.12 17.62 12.25 6.89 10.67

236.06 13.01 16.09 6.52 12.32 20.05169.14 10.14 15.67 11.53 8.52- 15.78259.00 11.51 15.85 8.93 11.38 15.91

282.70 17.16 26.17 9.95 12.60 14.70182.52 12.79 20.79 13.11 9.60 14.53310.32 15.11 22.42 13.05 12.35 11.98

206.42 20.23 20.54 13.09 14.48 15.25136.06 16.79 17.74 16.08 10.58 19.08233.44 17.00 20.60 11.03 13.89 12.82

350

POLYESTER ItOTTON YARNTEX - 12

1.00 No - 50

320

200

160

..

o---THICK PLACES.-NOR"Al PORTIONS

.-THIN PlACES

10 12 U.

ElONGATION, v,

120 LL- _

5 6 16

Fig. l=-Breaking strength and elongation at normal, thin andthick places of yarn

prominent in polyester blend. The lower elonga-tion arises because the break is completed earlierbecause of the lower strength of the thin portion.The drop in elongation from normal to thin por-

196

tion is most marked in polyester/cotton blendedyam. A flatter slope for strength-elongation rela-tionship is also seen in thin places for such yarns(Fig. 1). The same trend is found in 10 PIC and15 PIC yarns. Fig. 1 also shows a good correla-tion between strength and elongation for the threetypes of yarn samples. The correlation coefficientsfor normal, thin and thick places are 0.8443,0.7274 and 0.7925 respectively.

4 Conclusions

4,1 The diameter of thin places is around 70%and that of thick places more than 150% of thenormal yarn diameter. The actual diameter of thinplaces agrees very well with the calculated diame-ter but the actual diameter of thick places is muchhigher than the calculated diameter.4.2 The weight per unit length of thin place(at - 50% sensitivity level) is 60% while that ofthick place (at + 50% level) is around 150% ofthe normal yarn weight, indicating that the Ustercounts as thin places the portions thicker than thedesignated sensitivity level.4.3 Turns/em at thin place are 150'% and that atthick place 70% of the normal value.

GUPTE and BALASUBRAMANlAN: CHARACfERlSTICS OF IMPERFECTIONS IN YARNS

4.4 Hairiness at thin place is 35% and that atthick place 150% of the normal yam hairiness. In-crease in incidence of thick and thin places will,therefore, lead to higher variability in hairiness.4.5 The mean length of the fibres or CV/o of fi-bre length does not show any significant differ-ence at thin and thick places.4.6 Breaking strength of thin places is lower andthat of thick places higher than the normal yamstrength. The tenacity of thin places is also lowerthan that of normal yam, the effect being moreprominent in polyester/cotton blended yam.Thick place, however, has nearly the same tenac-ity as the normal yam.4.7 Elongation % of thick places is higher thanthat of the normal yam in cotton yam. Elongation% of thin place is lower than that of normal yam,the difference being more prominent in polyester/cotton blend.

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Textile Institute, Manchester) 1982, 33.2 Garde A R and Sethi J, Proceedings, 11th joint technolog-

ical conference of Al1RA, BTRA and SITRA (SouthIndia Textile Research Association, Coimbatore)1969,1.

3 PomfretWR, TextMonth, 10(1971)67.4 Subramanian T A, Bandyopadhyay S and Garde A R,

Proceedings, 13th joint technological conference ofAl1RA, BTRA and SITRA (Ahmedabad Textile in-dustry's Research Association, Ahmedabad) 1972, 63.

5 Bandyopadhyay S, Garde A R, Subramanian T A and RajB S,J TextAssoc, 33 (1972) 65.

6 Shankaranarayana K S, Govindarajulu K and Krishnaswa-my N, Proceedings, 14th joint technological conferenceof A l1RA , BTRA and SIrnA (South India Textile Re-search Association, Coimbatore) 1973,55.

7 BaIasubramanian N, Viswanathan K and Gupta K R, Prlrceedings, 17th joint technological conference of Al1RABTRA and SITRA (South India Textile Research As-sociation, Coimbatore) 1976,41.

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9 Gupta A K, Shah P H and Subramanian T A, Proceed-ings, 27th joint technological conference of ATIRABTRA, SITRA and NITRA (Northern India Textile Re-search Association, Ghaziabad) 1986,21.

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