Indian Journal of Textile Research

Vol. 8, June 1983,48-51

Effect of Yarn Structure on Fabric Stiffness

G S BHARGAVA

Technological Institute of Textiles, Bhiwani 125022

Received 28 January 1983; accepted 7 April 1983

The effect of structure of weft yarn on fabric stiffness has been investigated, keeping the warp yarn, fabric sell and weave

the same. Yarns of the same resultant count, but of seven different structures, first with single Z twisted, second and third 2-ply

and 3-ply single Z and folded Z twisted, fourth and fifth 2-ply and 3-ply single Z and folded S twisted, and sixth and seventh 2­

ply and 3-ply without folding twist, were used. It was observed that the 2-ply yarn with folding twist opposite to single yarn

exhibits maximum weft-wlly fabric stiffness and in general exhibits maximum stiffness. Increase in the number of plies from 2to 3 in folded yarn lowers the warp-way and overall fabric stiffness. In the case of parallel yarns, i.e. yarns without folding twist,

indrease in the number of plies has insignificant effect on warp-way, weft-way and overall stiffness of the fabric. Fabric having

warp and weft of the same twist direction has higher warp-way but lower weft-way stiffness compared to a fabric having warp

and weft of different twist directions, when the number of plies in. the yarn used is the same.

single's twist multiplier. Thus, in all, seven nominalsquare sett fabrics with a construction of 48 x 48,nearly 4.6 oz/yd 2 weight, using the same warp andseven different weft yarns, were prepared employingplain weave.

All the fabric samples were produced on the sameloom under identical conditions. The fabric sampleswere wet relaxed in an open trough containing 0.5;;~

Lissapol-D solution at 40°C for 30 min, rinsed twiceand then dried in relaxed state by spreading on theclean floor at 60°C atmospheric temperature.

Prior to testing, all the fabric samples wereconditioned in standard atmosphere (65 ± 5% RH and20 ±2eC temperature) for 48 hr.

The bending length of warp and weft directions ofeach fabric sample was determined using the Shirleystiffness tester. Ten specimens were tested for eachfabric sample to obtain mean values.

The flexural rigidity of warp and weft directions ofeach fabric sample was calculated using the followingrelation:

Table I-Characteristics of Yarns

Twist direction Twist multiplier

It is well established that the characteristics of a fabric

are dependent mainly on the type of fibre, yarn, weaveand fabric sett used and if the type of fibre, weave andfabric sett are the same, it is decided by the structure of

the yarn used.The aim of the present investigation was to ascertain

the influence of structure of weft yarn in terms ofnumber of plies, the direction of folding twist inrelation to single yarn and no folding twist on fabricstiffness, keeping the resultant count of weft and thequality of warp the same.

Several workers 1 -4 studied the effect of fibre

dimensions on fabric stiffness, but little information isavailable in the literature on the effect of number of

plies in yarn and twist of folding yarn on fabricstiffness.

Materials and Methods

Cotton-Shankar-4 cotton was used for making theyarn and fabric samples. The main characteristics ofthe cotton used were mean fibre length, 1.32 in; fibrestrength (Pressley index), 7.18 Ib/mg; and fibre

fineness~ 3.80 ,ug/in.Yarns'and fabrics-Cotton yarn of 205 count, spun

from Shankar-4 cotton using 3.2 twist multiplier and Ztwist, was used in warp direction. For weft direction,yarns of seven different structures, but the sameresultant count, first 205 single Z twisted, second andthird 2-p,ly (2/405) and 3-ply 0/605) single Z and foldedZ twisted, fourth and fifth 2-ply (2/405) and 3-ply(3/605) single Z and folded S twisted, and sixth andseventh 2-ply (2/405) and 3-ply (3/605) without foldingtwist, i.e, parallel ply yarns, were used (Table I). All thesingle yarns, i.e. 20' , 40' and 605, were spun with 3.8twist multiplier and the folded yarns with 80% of

48

Yarn

ref.

No.

W

IZ2Z3Z

2S

3S

2P3P

Yarn count

Nominal ActualSingleFoldedSingle

20'(warp)

19.15'Z-3.2

20'(weft)

18.85'Z-3.8

2/40'(weft)

18.25'ZZ3.8

3i60'(weft)

18.35'ZZ3.8

2/40'( weft)

18.85'ZS3.8

3/60'(weft)

18.75'ZS3.8

2/40'(weft)

19.95'Z 3.8

3,60'(weft)

19.10'Z-3.8 Folded

3.04

3.043.04

3.04

BHARGAVA: EFFECT OF YARN STRUCTURE ON FABRIC STIFFNESS

Flexural rigidity (dyne em) = 0.0981 W L 3

where W is the weight (gjm2) of the fabric; and L, the

bending length in em.

The fabric flexural rigidity per thread was' also

calculated for warp and weft directions of each fabric

sample to have a sound basis of comparison.

To observe the general effect of yarn structure on the

fabric stiffness, the overall flexural rigidity of each

fabric sample was calculated taking the geometrical

mean of warp and weft values as follows:

On comparing the warp-way bending length,

flexural rigidity and flexural rigidity per thread of I Z,

2Z and 3Z fabrics separately, it is found that 2Z fabrichas maximum values for these characteristics, while 3Z

fabric has minimum values. This shows that the use of

2-ply weft yarn having Z over Z twist results in higher

warp-way flexural rigidity as compared to single- and

3-ply weft yarns having Z over Z twist. This may be due

to greater bending resistance and frictional component

in 2-ply weft yarn compared to single- and 3-ply weft

Go = (Gl x G.z)Jwhere Go is the overall flexural ngidity, dyne em; G I'the warp-way flexural rigidity, dyne em; and G 2' the

weft-way flexural rigidity, dyne em.

Table 2~Significance of Difference Among the BendingLength Values of Different Fabric Samples

Warp-way

Fab~icIZ2Z3Z2S3S2P3PResults and Discussion

ref. No.Table 2 shows the significance of difference among

IZS,S,NSS,NSNSthe warp-way bending length values and weft-way

2Zs,NSS,SIS5

bending length values of different fabric samples. It is

3ZS,SIS,S,

observed that the differences in warp-way bending

2SSIS5NS

lengths are insignificant in the case of the following

3SS,S,

2PNS

fabric combinations: IZ with 2S, 2P and 3P; 2Z with 3P2S; 2P with 3P; and 2S with 3P. The differences in weft- Weft-wayway bending lengths are insignificant in the case of the

IZS,SISIS5NSNSfollowing fabric combinations: I Z with 2P and 3P; and

2ZS,S,S,SIS,3S with 2P.The-remaining fabric combinations exhibit

3ZS,SISISI

significant differences.

2SSIS,SI

The bending length, flexural rigidity and flexural

3SNSS5

rigidity per thread for both warp and weft directions

2PS5

3Pand the overall fabric flexural rigidity for all the seven SI . Significant at I;:, level;S5 . Significant at 5% level;and NS, Non-fabric samples are given in Table 3. significant.

Table 3-Bending Length and Flexural Rigidity Values of Experimental Fabrics

(Nominal construction, Reed x Pick: 48 x 48)

53.50

64.27

63.04

63.92

77.20

73.30

55.64

Overall flexuralrigidity, dyne cm

0.78

0.57

0.77

0.81

0.69

0.98

Weft

0.96

1.63

1.88

2.20

2.32

1.38

1.92

Warp2.00

Flexural rigidityper thread, dyne cm

39.84

38.44

39.51

33.28

29.52

49.19

Weft

47.96

Flexural rigidity,dyne cm

74.46

93.07

103.12

104.00

134.70

121.20

Warp112.00

WeftWarp

Bending length, cm

WeftWarp

IZ

2S

3S

Fabric Yarn typeref. No.*

2P

3P

20' 20' 1.99 1.50

(Z, Single) (Z, Single) (3.57)t (4.21)20' 2/40' 2.06 1.24

(Z, Single) (ZonZ, 2-ply) (3.11) (4.34)20' 3/60' 1.85 1.31

(Z,Single) (ZonZ, 3-ply) (3.03) (3.73)20' 2/40' 2.0 I 1.52

(Z,Single) (SonZ,2-ply) (2.76) (2.97)20' 3/60' 1.77 1.42

(Z,Single) (SonZ, 3-ply) (3.98) (3.46)20' 2/40' 1.97 1.43

(Z, Single) (Parallel) (4.31) (3.53)20' 3/60' 1.99 1.45

(Z, Single) (Parallel) (4.35) (3.61)

*Fabric reference number is just as yarn reference number and depends on the type of yarn used as weft in the preparation of the fabricsample.tThe values given in parantheses are CV%.

2Z

3Z

..

49

INDIAN J TEXT RES, VOL. 8, JUNE 1983

Fig. I-Overall flexural rigidity of IZ. 2Z and 3Z fabrics

Fig. 2-0verall flexural rigidity of IZ, 2S and 3S fabrics

•1Z 2Z 3Z

FABRIC

80

>' 80I- 0<!)0::--' E70

<f U 0:::::>'"xCw>---,lJU.60

--'--'<f0::W> 500 1 Z

2P3PFABRIC

>I-o<!)

0::

-' E 70<f U

<r '":::> Cx >,~lJ

U. 60

,; 80I­oQ0::

--' E 70~ u:::> '"x Cw>­--'lJU. 60--'--'<f0::W>o 50

-'--'<f0::W

2i 50

Fig. 3-0verall flexural rigidity of IZ, 2P and 3P fabrics

1Z 25 35FABRIC

maximum weft-way values along with the highest

value for overall fabric flexural rigidity (Fig. 4). Thisshows that the use of 2S yarn as weft would lead toimproved fabric stiffness as compared to 2Z or 2Pyarn.

On comparing the data for fabrics 3Z, 3S and 3P. itis observed that both warp-way and weft-way bendinglength, flexural rigidity and flexural rigidity per threadare maximum in 3P fabric. The warp-way values areminimum in 3S fabric, whereas the weft-way values areminimum in 3Z fabric. This shows that the use of three

parallel fine yarns. compared to twisted' yarn of thesame resultant count, leads to good fabric stiffness.This is further confirmed, as the value of the overall

flexural rigidity of 3P fabric is quite high compared tothe values for 3Z and 3S fabrics (Fig. 5).

yarns. On comparing the weft-way values of the samefabrics"it is found that I Z fabric has maximum valuesfor thel above characteristics, while 2Z fabric hasminimum values. This shows that increase in the

number; of plies in weft yarn, keeping the folding twistdirection and the resultant count the same, does notadd to stiffness of the fabric in the weft direction.

However, I Z fabric exhibits maximum overallfaocic flexural rigidity (Fig. I) among I Z, 2Z and 3Zfabrics. This clearly indicates that the use of single weftyarn is better in comparison to folded weft yarn havingmore plies and the same direction of folding twist.

On comparing the warp-way bending length,

flexural: rigidity and flexural rigidity per thread of IZ,2S and 3S fabrics, it is observed that 2S fabric has

maximl./m values for these characteristics, while 3Sfabric has minimum values. On comparing the weft­

way va~ues of the same fabrics, it is observed that 2Sfabric a~so has maximum values for these characteris­tics, while 3S fabric has minimum values. This shows

that the use of 2-ply, S over Z twist, weft yarn hasgreater effect on both warp- and weft-way stiffness ascompared to single and 3-ply, S over Z twist, foldedweft yarns. This may be due to greater bendingresistance and frictional component in the testdirection. The minimum stiffness in 3S fabric, in bothwarp and weft directions, may be due to the attainmentof morei circular shape in comparison to that in single­and 2-jply yarns and the resulting lower bendingresistance in the test direction.

The overall fabric flexural rigidity of 2S fabric ismaximum (Fig. 2) and this is due to the increasedvalues of flexural rigidity in both warp and weftdirections.

A comparison of the results for IZ, 2P and 3Pfabrics reveals that though the difference of the effectof chaQ.ged weft structure on bending lengths isinsignificant (Table 2). increased values of warp andweft flexural rigidity and flexural rigidity per thread areobtained using single Z twisted yarn, i.e. in 1Z fabric. Itis also observed from Fig. 3 that lZ fabric exhibitsmaximum value for overall flexural rigidity, whereas2P and 3P fabrics show nearly equal (Fig. 3), butappreciably lower values than lZ fabric. This trendshows that single yarn having Z twist is better for use asweft cOJ1lpared to fine parallel yarns having no foldingtwist, of the same resultant count, from the point ofview oflfabric stiffness in general.

On comparing the values of bending length, flexuralrigidity land flexural rigidity per thread of 2Z, 2S and2P fabrics separately, it is observed that 2Z fabricexhibits maximum warp-way values and minimumweft-way values for these characteristics, whereas 2Sfabric shows intermediate warp-way values and

50

BHARGAVA: EFFECT OF YARN STRUCTURE ON FABRIC STIFFNESS

Fig. 4-0verall flexural rigidity of 2Z. 2S and 2P fabrics

3Z 35 3PFABRIC

Fig. 5-0venill flexural rigidity of 3Z. 3S and 3P fabrics

AcknowledgementThe author is grateful to Shri M.K. Singhal and Shri

K.K. Agarwal for carrying out experimental work andto Prof. R.C.D. Kaushik, Director. TIT, Bhiwani, for

permission to publish this article.

(2) Square sett constructed fabric after wet­

relaxation treatment exhibits higher warp-waystiffness compared to weft-way stiffness.

(3) Warp-way stiffness is highest in the fabric having2-ply Z on Z weft yarn and is lowest in the fabrichaving 3-ply S on Z weft yarn.

(4) Weft-way stiffness is highest in the fabric having2-ply S on Z weft yarn and is lowest in the fabric having2-ply Z on Z weft yarn.

(5) Use of 3-ply weft yarn produces least stiff fabricand is independent offolding twist direction in relationto single yarn twist direction.

(6) In 2-ply weft yarn construction, Z on Z twistbrings down the fabric stiffness, while S on Z twistenhances the fabric stiffness.

(7) Use of 2-ply S on Z weft yarn produces fabric ofmaximum stiffness, and increase in ply, keeping theresultant count the same, leads to flexible fabric.

(8) Increase in the number of plies in the case ofparallel yarns, i.e. yarns having no folding twist, hasinsignificant effect on the bending length of fabric.However, in generaL the value of overall flexural

rigidity increases with increase in the number of plies.

2Z 25 2PFABRIC

;:- 80o':!a::

;:t ~ 70a::=> '"x. CUJ>'--'ulL.

--'--'<J:

a::UJ>o

~ 80o<,2

0::

;J E 700:: u=> '"XcUJ>.--'ulL. 60--'--'<J:

0::UJ>o 50

From the results for all the fabric samples, it isobserved that 2S fabric shows the maximum overall

flexural rigidity (77.20) and as such the use of two-foldyarn with S over Z twist is comparatively better forproviding better feel to the fabrics.

Conclusions

(1) Change in the structure of weft yarn has a markedinfluence on warp-way stiffness and marginalinfluence on weft-way stiffness.

ReferencesI Dowlene R P. Text Res J. 36 (1966) 80.

2 Cooper 0 N E. J Texl II/.H. 51 (1960) T 317.3 Cooper I:? N E. Texl Res J. 30 (1960) 150.4 Skelton J. J Text 11/.11.57 (1966) T 505.

51

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