effect of scouring and dyeing on physical properties of ...

~~~~~-C_H_E_M_1c_A_L_P_R_o_c_E_s_s_1N_G_--J~~~~~ EFFECT OF SCOURING AND DYEING ON PHYSICAL PROPERTIES OF THE FABRIC VERNEKAR SHRIKANT, KANADE PRAGNA, BHATTACHARYA SOMESHWAR AND MAIRAL ASHUTOSH Textile Enggineering Department, M S University, Baroda

INTRODUCTION

MATERIALS AND METHODS

RESULTS AND DISCUSSION

A well prepared base fabric is necessary for uniform dyeing. It is a well known fact that the cotton fabric shrinks on wet finishing due to swelling of fibres and so due to dimensional changes the· physical properties of the fabric changes.

Fabric was woven on the loom using 59 tex/2 yarn. (2/20 Ne) characteristics of yarn used are given in Table-1.

Some characteristics of the fabrics (grey ,scoured and dyed) are given in Table-2. The reed x pick is 40 x 36. After the fabric is scoured the

It has been reported that 70% of all the defects of the dyed and finished fabrics could be attributed to imperfect preparation of the fabric 1 • Adams2 emphasized the importance of effective scouring for all cotton and cotton/polyester blended fabrics for subsequent dyeing and finishing. A thoroughly prepared cotton fabric should have total non - cotton content less than 1 .5% and absorbency of less than 2 seconds. Varghese et al have studied the effect of scouring on dyeing of cotton fabrics 3 . They have studied the physical and other properties of ttie fabric (after scouring) . It should be noted that they have not taken into account the change in the crimp percentage in the fabric in explaining the changes in the physical properties of fabric, so attempts have been made here to study the changes in physical properties of the fabrics at each stage i.e., after weaving, scouring and dyeing.

Table - 1 : Yarn Characteristics Yarn count

Tex Ne

59 tex/2 2/20

Breaking load

gms

655

Breaking elongation

O/o

6.95

Twist

TPC TPI TM

5.0 12.72 4.14

Fabric was scoured taking 30gpl NaOH and soap (Lissapol N) 20 gpl. One portion of scoured fabric was dyed in a bath containing 2% shade (direct dye) 15 gpl glauber's salt and soda ash . Air permeability of fabric was measured on Metefem air permeability tester. Breaking load and breaking elongation was measured on lnstron tensile tester. Tearing strength of fabric was measured on lnstron. Bursting strength was determined on Ubique bursting strength tester. Bending length was measured on Shirley Stiffiness tester.

Journal of the Textile Association - Nov.-Dec. 2005

fabric shrinks. The warp and weft crimp increases after the scouring , so threads/cm also increases. There is increase in weight of the fabric in terms of gm/m 2 from 190 to 212 gm/ m2 • (from grey to scoured fabric). This is mainly due to increase in threads /cm. After dyeing also wt/m 2 increases, but not significantly. Also there is increase in thickness of fabric from 0.568 mm to 0.642 mm (after scouring) . Since there is increase in crimp and threads/cm the fabric thickness also increases. After dyeing the fabric thickness is more than grey fabric, but slightly less than scoured fabric. It seems that removal of fat and waxes or dye pick-up has 173

Table - 2 : Characteristics of the Fabric (Reed x Pick : 40 x 36) Grey

1600

Dyed

Scoured

~ 1200

.

:a

Ends/cm

17.09

17.72

18.11

(Ends/inch)

(43.4)

(45)

(46)

l

Picks/cm

15.74

17. 32

16.93

~ 400

(Picks/inch)

(40)

(44)

(43)

Cloth cover factor

26.39

28.16

28.17

Warp crimp%

15

21

22

8

14

13

190

212

219.5

0.568

0.642

0.634

•

800

0 Orey

Weft crimp % Weight (gm/m

2

)

Thickness( mm)

no significant effect on changes in weight/m 2 or thickness of the fabric but dimensional changes have major effect on these parameters.

is attributed to change in cloth cover and swelling on fibres in wet processing.

Table - 3 : Physical Preparation of the Fabric

3

Grey

Scoured

Dyed

1590

703

620

Warp

3.91

4.13

4.39

Weft

3.91

4.44

4.39

5.5

6.7

6.6

Warp

43.2

41.6

45

Weft

38

43

41

Warp

18.98

21 .98

23.58

Weft

11.88

15.04

16.63

Warp

2.7

1.8

1.94

Weft

2.94

2.08

2.0

2

Air permeability (m /m /hr) Tearing strength (kg)

Bursting strength (kg/cm

2

)

Breaking load (kg)

Breaking extension (%)

Bending length (cm)

Air permeability of the grey fabric is 1590 m3/m 2/hr and that of scoured fabric is 703 m3/m 2/hr. So there is substantial drop in air permeability (Fig-1 ). This is du~ to the fact that

m 3/m 2 /hr. There is drop in permeability from scoured to dyed fabric but it is not as significant as between grey and scoured fabric. The overall drop in airpermeability

Table - 4 : Tensile Properties of the Yarn Removed from Fabric

Warp

Weft

174

Grey

Scoured

Dyed

Breaking load (gms)

528

566

543


5.35

5.98

6.70

Breaking load (gms)

611

632

541


5.40

5.92

5.99

Dyed

Fig. 1 : Effect of Scouring and Dyeing on Air Permeability of Fabrics

threads/cm are higher in scoured fabric than grey fabric and so cloth cover-factor of scoured fabric is higher, so less air is allowed to pass through fabric and hence there is substantial ·drop in air permeability. Air- permeability of dyed fabric is 620

Physical properties of the grey, scoured and dyed fabrics are given in Table-3.

Scourwd

Tear strength for warp is 3.91 kg grey and 4.13 kgs for scoured fabric. Also tear strength for weft is 3.91 kgs for grey and 4.44 kg for scoured fabric. So there is increase in tearing strength after scouring . Tearing strength depends upon single thread strength and on ability for close grouping of the threads under force of threads4 • So it is necessary to know the effect of sourcing on the individual threads, hence the tensile properties of the threads removed from the fabric (after scouring and after dyeing) were determined and all given in Table - 4. The tensile strength of yarn increases after scouring. (Warp from 528 to 566 gms and weft from 611 to 632 gms). Since tearing strength depends upon the tensile strength of yarn, there is a increase in tearing strength after scouring. After dyeing , there is no specific trend for tearing strength . For warp, tearing strength increases and for weft, it decreases. This may be due to decrease in tensile strength of yarn after dyeing and changes in thread spacing. Breaking load for warp and weft do not show any specific trend for scoured and dyed fabric, J.Varghese et al3 also obtained similar results . Breaking extension of fabric in warp direction of grey, scoured and dyed fabric is 18.98, 21 .98, 23.58 percentage and in weft it is 11 .88 , 15.04, 16.63 percentage respec-


tively. There is increase in breaking extension % of warp as well as weft after scouring and after dyeing (Table - 4) also warp and weft crimp increases after scouring and dyeing so together there is rise in breaking extension of fabric . Bursting strength of grey fabric is 5.5 kg/cm 2 and scoured fabric is 6.7 kg/ cm 2, so there is increase in bursting strength after scouring (Fig.2). after dyeing it is 6.6 kg/cm 2, that means

l·•

{. ii! 4

Fig. 2 : Effect of Scouring and Dyeing on Bursting Strength of Fabrics

there is no significant change after dyeing, it remains almost same. Bursting strength depends upon the crimp% of the warp and weft in the fabric and also on yarn strength and its extensibility. Warp crimp and weft

crimp increases after scouring and hence bursting strength increases. After dyeing warp and weft crimp is not much different than scoured fabric and even though breaking extension of yarn improves after dyeing ; the yarn strength decreases, so the combined effect of all these factors is that there is no significant change in · bursting strength after dyeing. Bending length (in warp and weft direction) is lower after scouring. There is a increase in threads/cm in the fabric after scouring, so it was expected that the stiffiness of fabric will increase. So it is possible that removal of fats and waxes has a effect on the stiffness of the fabric. After dyeing change in bending length do not show specific trend, but bending length is less compared to grey fabric. CONCLUSIONS After scouring there is increase in crimp of warp and weft and hence increase in thread density. So there is increase in weight per sq . meter

and thickness of the fabric. After dyeing, there is no significant change in crimp and so there is no specific or significant change in wt/m 2 thickness of the fabric etc. There is substantial drop in airpermeability of the fabric after scouring due to the increase in cloth cover and swelling of fibres in wet processing. Fabric becomes less stiff after the scouring possibly due to the removal of fats and waxes. Bursting strength improves after scouring of the fabric as there is increase in warp and weft crimp and also due to increase in yarn strength and extension. REFERENCES: 1. Turner G.R, Texttile Chemists and Colorists, 246 (1981). 2. Adams M.D, American Dyestuff Reporter, 19 No. 7 (1978) . 3. Verghese J., Indian Textile Journal, 97 (1984) 4. Booth J.E., Principles of Textile Testing, 436.

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