EFFECT OF FIBRE QUALITY INDEX ON SPIRALITY OF WEFT

KNITTED FABRICS Prof.V.KRISHNAKUMAR, Kumaraguru College of Technology

e-mail : Kitcha27@yahoo.com

Dr.B.S.DASARADAN, PSG College of Technology

Dr.V.SUBRAMANIAYAM, Director, Jaya Engg. College

1 INTRODUCTION

The main factor, which is responsible for spirality in weft-knitted

fabric, is yarn twist liveliness. Twist liveliness is a yarn property which gives an

indication of torsional energy present in the yarn. It is dependent on the yarn

twist; the maximum value of twist liveliness occurs for higher twist content.

Since spirality appears generally in knitted fabrics produced from single yarns,

it was decided to produce a range of single yarn samples from cotton having

different FQI values with different twist factors with a view to investigating the

effect of FQI,twist and twist liveliness on spirality.

2 MATERIALS AND METHODS

2.1 Raw Material details

For the study 4 types of Cotton were used. The Specifications of

Cotton are given in Table 1.

TABLE 1 COTTON SPECIFICATIONS

S.No. Description Sample A Sample B Sample C Sample D

1. Raw Material Cotton (single yarn cone form)

Cotton (single yarn cone form)

Cotton (single yarn cone form)

Cotton (single yarn cone form)

2. Cotton Variety LRA S4 LK MECH

3. Station Guntur Gujarat Adoni Chitoor

4. Fibre parameters

a) 2.5% span length (mm)

26.9 28.7 26.7 26.3

b) 50% span length (mm)

13.5 14.3 13.7 13.6

c) Uniformity Ratio

0.5 0.498 0.51 0.52

d) Fineness Value (Micrograms/inch)

3.6 3.2 3.7 3.5

e) Strength (g/Tex)

21 22 21 22

f) Trash % 4.6 3.9 4.3 4.5

g) Maturity 0.82 0.84 0.83 0.81

2.2 Yarn production

The cotton was passed through a blow room, carded on a card

equipped with metallic wire. The carded sliver was passed through 2 draw

frame passages. Thereafter it was passed through simplex and spun to 30s

(19.68 tex) with 3 TM levels viz. 3.2,3.5 & 3.8 in a ring frame.

2.3 Fabric production

All the fabrics knitted are of single jersey type. Each yarn was

used to knit a length of knitted fabric. The following weft knitting machines were

used for the production of fabrics. A 17" diameter single jersey machine with 24

feeders, 24 gauge, with total number of needles 1284 and speed 24 rpm; this

was employed for knitting 30s yarn. The machine had a positive feed device.

The Particulars of Weft knitted fabrics are given in table 2.

TABLE 2 PARTICULARS OF WEFT-KNITTED FABRICS

Knitting - process parameters

Wales/inch 30

Course/inch 36

Stitch length (cm) 0.2

TIGHTNESS FACTOR (Tex0.5 cm-1) 14.1

2.4 Spirality Testing

For measuring spirality, the pillow case method as suggested by

AATCC-179 2001. Standard was used; In this, from a specimen consisting of

two layers of 380 x 380 mm, pairs of 250 x 250 mm were marked perpendicular

to the length of the specimen. A line is drawn through each of the four sets of

adjacent benchmarks so that a square is formed. The specimen was tumble

washed in a tumbler and then relaxed on the table before measuring spirality.

3 RESULTS AND DISCUSSION

3.1 Yarn quality parameters

Table 3 gives the relevant characteristics of the Yarn samples

produced for the study.

TABLE 3

YARN CHARACTERISTICS

Yarn Parameters Sample A Sample B Sample C Sample D

Count 30.03 30.04 30.29 30.38

Lea Strength (lbs) 62 63 71.5 64

C.S.P. 1861 1898 2166 1940

Count CV% 0.894 0.921 0.921 0.987

Strength CV% 4.561 4.273 4.715 3.56

U% 9.33 9.13 8.14 9.22

Thin places 0.0 0.0 0.0 0.0

Thick places 6.3 5.9 0.0 5.0

Neps 30.0 32.0 7.5 22.5

Total 36.3 37.9 7.5 27.5

TPI 21.9 22.295 21.56 21.22

TPI CV% 2.95 2.56 3.264 3.112

3.2 Effect of Twist level on Twist Liveliness Using Twist Liveliness tester the twist liveliness value was checked in all the

samples on the details are given in Table 4.

TABLE 4 YARN TWIST LIVELINESS VALUE (cm)

Sample Twist Liveliness (cm) at 3.2 T.M

Twist Liveliness (cm) at 3.5 T.M

Twist Liveliness (cm) at 3.8 T.M

A 19.69 25.99 28.96

B 17.82 21.54 23.56

C 23.14 27.69 30.76

D 19.62 22.24 27.71

The results reveal that there is almost a linear relationship between the

level of twist and twist liveliness values. With increasing T.M value the twist

liveliness values increase. The reason for this linear variation is due to the

amount of energy stored in twisting. Higher the twist liveliness, greater will be

the energy stored

3.3 Effect of Raw Material on Twist Liveliness

The influence of FQI value of raw material on Twist liveliness was

also studied. The details are given in Table 5.

TABLE 5

YARN TWIST LIVELINESS VALUE (cm)

T.M Values Sample A (LRA)

FQI-64.3

Sample B (S4)

FQI -81.21

Sample C (LK)

FQI-64.15

Sample D (MECH)

FQI-69.63

3.2 19.69 17.82 23.14 19.62

3.5 25.99 21.54 27.69 22.24

3.8 28.96 23.36 30.76 27.71

For the given twist level, the twist liveliness values show variation.

From the study it is found that the yarn produced from a cotton having a higher

FQI (S4) shows minimum twist liveliness value whereas the coarse fibre a

lower FQI shows higher Twist liveliness value. This reveals that coarser the

fibre, the twist liveliness value will be more. And also, the resistance offered by

the coarser fibre in twisting is more.

3.4 The Effect of Twist Liveliness on Spirality.

The Knitted fabric samples were washed, tumble dried and relaxed

to measure spirality angle as mentioned above. The values of spirality in

degrees are tabulated in Table 6.

TABLE 6 EFFECT OF TWIST LIVELINESS ON SPIRALITY

A B C D

T.M 3.2 3.5 3.8 3.2 3.5 3.8 3.2 3.5 3.8 3.2 3.5 3.8

Twist Liveliness (CM)

19.69 25.99 28.96 17.82 22.24 27.71 23.14 27.69 30.76 19.62 21.54 23.55

Spirality (Degree)

4.2 6.5 7.3 3.6 6.1 6.9 5.9 7.1 7.3 4.9 5.1 5.6

From the table 6 , It is clearly observed that higher the twist liveliness

value, the severity of spirality also becomes higher. For twist liveliness value of

17.82, the spirality is 3.6, for the maximum twist liveliness value of 17.82, the

spirality is 3.6 and for the maximum twist liveliness value of 30.76 the spirality is

4 CONCLUSION

The Study reveals that the twist liveliness value is linearly varying

with the amount of twist present in yarn in all the samples irrespective of FQI

values. As for as raw material is concerned fibre having higher FQI value

results in lower twist liveliness which finally resulted in decresed spirality of

weft knitted fabrics. The Fibre with FQI value of 81 .21 and with 3.2 TM level

resulted in minimum spirality of 3.6o among all the samples.

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