ANNALS OF THE UNIVERSITY OF ORADEAFASCICLE OF TEXTILES, LEATHERWORK

INFLUENCE OF FABRIC TIGHTNESS ON SPIRALITY OF WEFT-KNITTED PLAIN FABRIC

A.K.M. Mobarok Hossain. 1

1Ahsanullah University of Science and Technology, Dhaka,Bangladesh. mobarok_textech@yahoo.com

Abstract: Global demand for knitted garments is growing at a faster rate than that of woven items.Currently around 50% of clothing needs in the developed countries is met by knit goods. So ensuring the required quality in a knitted fabric is a vital issue for the manufacturer. One of the major problems encountered in knitted fabricis spirality. It affects particularly single jersey fabric and presents a serious problem during garment confection and use. So controlling spirality is a basic requirement for producing quality knitted fabric. Though there are several factors that contribute to knitted fabric spirality, yarn twist and relative tightness of the fabric are said to be the most significant ones. In this work plain jersey fabrics were produced by a Hosiery knitting machine and spirality values were observed for different T.P.I. and tightness factor at relaxed state. It was found that tightness factor has a direct influence on knitted fabric spirality with a high degree of correlation. The work thus gives an idea to deal this problem by controlling the knitting parameters.

Key words: Knitted Fabric, Spirality, Tightness Factor, Yarn Count, T.P.I, Stith Length, Regression

1. INTRODUCTION

Spirality is a distortion of a knitted fabric whereby the wales and courses align at an angle other than 90◦.Terms such as “fabric skew”, “fabric torque” are also used to describe fabric spirality [4]. It is a critical problem for single jersey structure and creates significant problems at the clothing step. Though the general tradition for solving the problem is to follow special method during finishing but this type of prevention does not last longer and therefore not helpful for quality manufacturing.

There are two factors that are responsible for the deviation from 90◦ between courses and Wales. Due to spiral arrangement of the courses in the fabric, multifeeder machines show a distortion from 90◦ in course-wale alignment, which is known as ‘Pattern Drop’.It is a characteristic of the machine rather than the yarn. Deviation from 90◦ can also be caused by twisting of the wales where yarns have residual torque. The term ‘Spirality’ originally refers to such type of deviation [1].

Besides the torque, spirality is also governed by fabric tightness, fibre parameter, yarn formation system and fabric finishing [5]. The influence of fabric tightness can be understood easily from the sense that tightness contols the yarn and loop movement and thus affect any distortion. Fabric tightness of the knitted fabric is generally expressed by Tightness Factor which is a measure of the relationship between the loop length of a knitted fabric and the count of the yarn employed to construct it. The usual formula is:

Tightness Factor ( T.F.) = in SI unit.

As loop length and yarn count are two great knitting parameters, an experimental work on knitted fabric spirality with respect to tightness factor will provide the knowledge to control this problem from the knitter’s side.s

2. EXPERIMENTAL PROCEDURE

The experimental work has been done in the laboratory of Ahsanullah University of Science and Technology. All the test procedure has been performed according to following sequences.

1. Cotton yarn cones of five different counts (20/1 Ne, 24/1 Ne, 26/1 Ne, 30/1 Ne and 32/1 Ne, were taken. Twists per inch (T.P.I.) of these yarns were determined by Quadrant Twist Tester.2. Plain jersey fabric of different stitch lengths were produced by different counts of yarn in a Hosiery knitting machine. In this way a total of twenty (20) samples of different tightness factor were obtained. The produced fabrics are almost free of ‘Pattern Drop’ as the machine is of single-feeder type.Stitch lengths of these samples were measured by HATRA Course LengthTester.3. The samples were subjected to dry relaxation procedure (temperature: 27˚c, relative humidity: 65%, Time: 48hours.) So samples were obtained at dry relaxed state. 4. Spirality of those fabrics were measured very cautiously by protractor (according to the CTI test mehod[1]) and noted against the corresponding tightness factors.5. Relation between fabric tightness and spirality were shown by graphical and statistical analysis

3. RESULTS

Table 1 shows the summarized results obtained through the experimental procedure

Table 1: Spirality values against different tightness factors for the observed knitted samples

Fabric Sample

No.Yarn T.P.I.

Yarn Count (Ne)

Stitch length(mm)

Tightness factor(in SI

unit)

Measured Spirality

1

15.1 20/1

7.88 .69 41°2 6.03 .90 36°3 4.92 1.104 27°4 4.69 1.160 23°5

18.2 24/1

7.76 0.640 48°6 6.08 0.816 38°7 4.96 1.00 31°8 4.82 1.03 27°9

18.5 26/1

8.27 0.576 45°10 6.49 0.734 35°11 5.00 0.953 30°12 4.74 1.005 26°13 19.5 30/1 8.26 0.535 55°

2

ANNALS OF THE UNIVERSITY OF ORADEAFASCICLE OF TEXTILES, LEATHERWORK

14 6.09 0.727 40°15 4.94 0.896 33°16 4.66 0.950 27°17

21.6 32/1

8.32 0.516 46°18 6.49 0.662 40°19 4.95 0.868 35°20 4.74 0.906 31°

4. GRAPHICAL REPRESENTATION OF RESULTS WITH STATISTICAL ANALYSIS

The obtained results were analyzed with the help of Microsoft Excel advanced features (Chart wizard and Data analysis toolpack). Following figures with statistical analysis were obtained for yarns of different T.P.I.

0.69, 41

0.9, 36

1.104, 27

1.16, 23

0

5

10

15

20

25

30

35

40

45

0 0.2 0.4 0.6 0.8 1 1.2 1.4

T.F.

Sp

iral

ity(

in d

egre

e)

Figure2: Tightness factor vs. spirality with trend line for 20/1 Ne (T.P.I. =15.1)

Table 2: Statistical analysis for figure2

Regression StatisticsMultiple R 0.983416456R Square 0.967107926Adjusted R Square 0.950661889Standard Error 1.826043269Observations 4

0.64, 48

0.816, 38

1, 31

1.03, 27

0

10

20

30

40

50

60

0 0.2 0.4 0.6 0.8 1 1.2

T.F.

Sp

iral

ity

( in

deg

ree)

Figure3: Tightness factor vs. spirality with trend line for 24/1 Ne (T.P.I. =18.2)

Table 3: Statistical analysis for figure3

Regression StatisticsMultiple R 0.992195933R Square 0.98445277Adjusted R Square 0.976679154Standard Error 1.405168408Observations 4

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ANNALS OF THE UNIVERSITY OF ORADEAFASCICLE OF TEXTILES, LEATHERWORK

0.576, 45

0.734, 35

0.953, 30

1.005, 26

0

5

10

15

20

25

30

35

40

45

50

0 0.2 0.4 0.6 0.8 1 1.2

T.F.

Sp

iral

ity

(in

deg

ree)

Figure4: Tightness factor vs. spirality with trend line for 26/1 Ne (T.P.I. =18.5)

Table 4: Statistical analysis for figure4

Figure 5: Tightness factor vs. spirality with trend line for 30/1 Ne (T.P.I.=19.5)

Table 5: Statistical analysis for figure5

Regression Statistics

Multiple R 0.990427276R Square 0.980946189Adjusted R Square 0.971419284Standard Error 2.03982253Observations 4

Regression StatisticsMultiple R 0.97612939R Square 0.952828586Adjusted R Square 0.92924288Standard Error 2.182730576Observations 4

0.516, 46

0.662, 40

0.868, 35

0.906, 31

0

5

10

15

20

25

30

35

40

45

50

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

T.F.

Sp

iral

ity

(in

deg

ree)

Figure 6: Tightness factor vs. spirality with trend line for 32/1 Ne (T.P.I.=21.6)

Table 6: Statistical analysis for figure6.

Regression StatisticsMultiple R 0.983418659R Square 0.967112259Adjusted R Square 0.950668389Standard Error 1.439419207Observations 4

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ANNALS OF THE UNIVERSITY OF ORADEAFASCICLE OF TEXTILES, LEATHERWORK

0

10

20

30

40

50

60

0 5 10 15 20 25

Yarn T.P.I.

Sp

iral

ity

( in

deg

ree)

)

LOWER

HIGHER

FABRIC TIGHTNESS

♦ Spirality Value

Figure 6: Summarized graphical representation showing the relationship between spirality and tightness factor for yarns with different T.P.I. 5. DISCUSSION ON RESULTS:

1. From the obtained graphical diagrams it was found that tightness factor (T.F) has a direct influence on spirality,i.e. spirality increases due to decrease of tightness factor and spirality decreases due to increase of tightness factor.It may be also commented that for the same yarn count if stitch length is increased then spirality will be increased and vice-versa.It may also be commented that for the same stitch length if yarn count is increased then spirality will be decreased and vice-versa.

2. The values of spirality were too high as fabric tightness values were very low(less than 1 in most cases). However in commercial production environment, fabrics are generally knitted with optimum tightness factor (near 1.5) and the amount of spirality is generally controlled within 10°. [2]

3. For all cases, R2 values were obtained within the range 0.95-.98 indicating a high degree of correlationship between the tightness factor (T.F.) and the spirality. Standard error (Se) values are also found within acceptable limits. These express the ‘goodness of fit’ of the drawn trendline[3].So any value of spirality for different tightness factors for a given T.P.I. may be guessed very accurately from the obtained trendline.

4. The summarized figure (Figure 6) represents the whole results in a concise form showing the relationship between spirality and tightness factor for yarns with different T.P.I.

6. CONCLUSION :

The work shows that knitted fabric spirality increases or decreases according to decrease or increase in fabric tightness. So it is possible to control spirality by changing the tightness factor of a knitted fabric. But as tightness factor also influence fabric dimension and performance i.e. width, G.S.M and

shrinkage; controlling spirality by changing tightness factor must be done very carefully so that other quality parameters do not exceed acceptable limits. Otherwise the knitter should consider knitting fabric with yarns of lower T.P.I.It should be remembered that this type of distortion can not be eliminated but must be controlled within the acceptable limit.Acknowledgments :

The present work was executed at the Knitting and Q.C.Laboratory of Ahsanullah University of Science and Technology, Dhaka. The author would like to thank the laboratory stuff and the students taking the project work under his supervision in Spring10 semester for their co-operative hands.

REFERENCES

[1]. Cotton Technology International : The STARFISH Apprroach to High Quality Cotton Knitgoods, User-Manual Version 88:1, U.K.1988[2]. Brackenbury, T.: Knitted Clothing Technology, 1st Edition, and Blackwell Science Limited U.K. 1992[3]. Eppen, G.D., Gould, F.J., Schimdt,C.P., Moore, Jeffrey H., Weatherford, Larry R. : Introductory Management Scienc, 5th edition, Prentice Hall Inc., USA, 1998 .[4]. Badr, Alaa Arafa, El-Helw, Elsayed, El-Hawary,Ibrahim, Mito,Abo Baker,Elmogahzy, Yehia, Farag, Ramsis: Dimensional stability of Cotton fabric with emphasis on spirality: between the theory and the practice,Beltwide Cotton Conferences, Nashville,Tennessee, January 8-11, 2008[5].Das,Subrata : Causes and Remedial Measures of Spirality in Knitted Fabrics, http://www.fibre2fashion.com/industry-article/16/1567/causes-and-remedial-measures-of-spirality- in-knitted-fabrics1.asp

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