121201-6969-ijet-ijens.pdf

International Journal of Engineering & Technology IJET-IJENS Vol: 12 No: 01 5

121201-6969 IJET-IJENS @ February 2012 IJENS I J E N S

Advantages of Prewashed 100 % cotton knit fabric over Scoured –

Bleached fabric in deep color Reactive dyeing process.

Asma Begum

Ahsanullah University of Science and Engineering

Department of Textile Engineering

141 – 142 Love Road, Tejgaon Industrial Area

Dhaka - 1208

Abstract : Natural fibre like cotton contains oils , fats , waxes , minerals , leafy matter

and motes as impurities and natural color , all are removed by scouring and bleaching

process from cotton knit fabric which reduces fabric qualities and other properties. So it

is possible to achieve similar or better results from deep color Reactive dyeing of

prewashed fabric to dyeing of Scoured–bleached fabric. Prewash is done with Oleic acid

based wetting agent which is biodegradable, low foaming, lubricant with leveling,

dispersing and emulsifying properties. Examinations have shown higher values of color

fastness to wash, similar rubbing fastness, higher color strength as well as reduction in

weight loss, better strength and softness of fabric can be achieved from prewashed

dyed fabric.

Key Words: Prewash, Burst strength, Bending length, Wash fastness to color, Rubbing.

INTRODUCTION

Cotton fibres mainly consist of cellulose (94%), small amounts of other compounds like

Protein (1.3%0,Ash(1.2%),Wax (0.6%0, Sugar (0.3%), Pigments (Traces) and others

(2.6%).Cotton fabrics are affected by strong acid and boiled in a dilute solution of an

alkali like caustic soda , in the presence of air , the cotton turns yellow and lose strength

slightly. Scouring process removes water insoluble materials such as oils, fats, and waxes

from the cotton fabric. Oils and Fats are removed by Saponification with hot Sodium

Hydroxide solution. Unsaponifiable materials such as waxes and dirt are removed by

Emulsification. Depending on the amount of impurities and the reaction and wash

conditions, the loss in weight of the raw cotton material due to boil – off can reach up to

seven percent or even higher in case of high – impurity cotton. Cotton, like all natural

fibres, has some natural coloring matter, which confers a yellowish brown color to the

fibre. The purpose of bleaching is to remove this coloring material and to confer a white

appearance to the fibre. Hydrogen peroxide is the most useable bleaching agent. It is a



corrosive, oxidizing agent which may cause combustion when allowed to dry out on

oxidizable organic matter. Decomposition is accelerated by metal contamination and

accompanied by the liberation of heat and oxygen, which will support combustion and

explosions in confined spaces. The material is an irritant to the skin and mucous

membrance and dangerous to the eyes. Hydrogen peroxide is a weak acid and ionizes in

water to form a hydrogen ion and a perhydroxyl ion. The perhydroxyl ion is the active

bleaching agent. Hydrogen peroxide can also decompose .This reaction is catalyzed by

metal ions. This reaction is not desired in bleaching because it is an ineffective use of

hydrogen peroxide and causes fibre damage. At PH 10.2 to 10.7 is optimum for

controlled bleaching. Sodium hydroxide is used to obtain the proper PH.

There are risks to get the below problems in Scouring and bleaching process:

1. Harsh handle

2. Yellowing the goods

3. Fibre degradation or reduction in fibre strength

4. Pinholes , broken yarns , tears

5. Resist spots

6. Loss in voluminous character of the material

7. Decrease in the elasticity of the materials

8. Low sewability of the materials

9. Weight loss

Above problems can overcome using oleic acid based product (Humectol C , Clariant) for

cotton washing instead of scouring – bleaching.

Oleic acid is a mono unsaturated, straight chain C18 fatty acid (double bond in between

C9 and C10) . It occurs in almost all natural fats. Most oleic acid is obtained from animal

tallow or vegetable oils. It is a yellow to red oily liquid with lard like odour and darkens

on exposure to air. It is immiscible with water but miscible with alcohol, ether and other

organic solvents. It is a solvent for oils, fatty acids and oil soluble compounds. The fatty

acid is obtained from fats by hydrolysis followed by steam distillation and separation by

crystallization or solvent extraction. Filtration from the press cake gives the oleic acid –

triethanolamine soap, which is an emulsifier for mineral oil. After esterifying and

sulphonating, wetting agents and leveling agents can be made from oleic acid. Humectol

C liquid high concentrate is a yellow – brown liquid, preparation based on oleic acid,

anionic, dilutable with water in any proportion which is bio-degradable, low foaming

wetting agent and lubricant with leveling, dispersing and emulsifying properties.



If raw cotton materials are washed with only Oleic acid based product can be get below

advantages:

1. Soft fabric

2. Minimum strength loss

3. Minimum weight loss

4. Less amount of dyes used

5. Less chemicals used

6. Less softener used

7. Short time

8. Easy process

9. Increase production

10. Better fastness

SAMPLE PREPARATION

For this experiment 100 % cotton, 175 GSM, Single Jersey knit fabrics were pretreated

according to Prewashing recipe and Scouring – bleaching recipe and after that Black,

Brown and Red shades were dyed on both prewashed fabrics and Scoured – bleached

fabrics with reactive dyes. After pretreated, weight loss and CIE whiteness were studied.

After dyeing Burst strength, Bending length, Wash fastness to color, Rubbing fastness

tests had done.

EXPERIMENTAL PART

Throughout this study, the following materials were used.

Fabrics : 100 % cotton knit single jersey , 170 GSM

Chemicals & Dyes : Oleic acid based wetting agent (Humectol C liquid high conc,Clariant),

Wetting and detergent (Imerol PCLF, Clariant), Sequestering agent Sirrix 2UD, Clariant ),

Stabilizer ( Stabilizer SOF , Clariant ) , Sodium Hydroxide , Hydrogen Peroxide 50 % ,

Acetic acid , Peroxide killer ( Bactisol ARL, Clariant ), Glauber’s salt, Soda ash, Washing

off agent ( Ladipur SP , Clariant ) , Reactive dyes ( Drimaren yellow CL – 2R, Drimaren

Red CL – 5B , Drimaren Blue HF – RL, Drimaren Black CL – S , Clariant ).

Prewashing recipe: Grey cotton was washed with 0.50 gm/l Humectol C liquid high

concentration at 98 ᵒ c for 40 min and washed and Black, brown, red shades were dyed

on this fabric.



Scouring and bleaching recipe: Treated the fabric with 1.00 g/l Imerol PCLF, 1.00 g/l

Sirrix 2UD, 0.80 g/l Stabilizer SOF, 2.50 g/l Sodium Hydroxide, 2.50 g/l Hydrogen

peroxide 50 % at 98 ᵒ c for 60 min, after hot wash , neutral the fabric and treated with

0.20 g/l Bactosol ARL at 40 ᵒ c for 10 min , wash .

Dyeing: Both type of pretreated fabrics are dyed the below recipes.

Black colour recipe : 5 % Drimaren Black CL –S , 80 g/l Glauber’s salt , 20 g/l Soda ash ,

Isothermal 60 ᵒ c method

Brown color recipe : 2.00 % Drimaren Yellow CL-2R , 0.80 % Drimaren Red CL – 5B , 0.50

% Drimaren Blue HF – RL , 80 g/l Glauber’s salt , 20 g/l Soda ash , Isothermal 60ᵒ c

method.

Red color recipe : 0.60 g/l Drimaren Yellow CL- 2R , 2.00 % Drimaren Red CL – 5B , 0.20

g/l Drimaren Blue HF – RL , 80 g/l Glauber’s salt , 20 g/l Soda ash , Isothermal 60 ᵒ c.

After dyeing cold wash, neutral and soaping had done and normal dried the fabrics.

DATA ANALYSIS

Weight loss:

Weight loss of prewashed fabric is 4 % and Scoured – bleached fabric is 6 %.

CIE Whiteness Index, D65, 10 Deg : Prewashed fabric is 9.01 and Scoured and bleached

is 74.75 .

Burst Strength Test:

Table 1

Prewashed dyed fabric

Shade Name Time in second Burst strength kpa Average kpa

Black 21.17 680

Brown 21.22 690 690

Red 21.3 700

Table 2

Scoured – bleached dyed fabric

Shade Name Time in second Burst strength kpa Average kpa

Black 20.18 620

Brown 20.25 630 633.33

Red 20.12 650

From above two tables it is clearly studied that prewashed fabrics are stronger than

scoured – bleached fabrics.



Bending Test: (BS3356 BS 9073 Part 7 and ASTM D 1388 )

Shirley Stiffness Tester m/c

Bending length is a property of a fabric related to stiffness. It is the length of the fabric

that will bend on its own weight to a definite extend. A high value of bending length

corresponds to a stiff fabric and vice versa.

Table 3

Prewashed dyed fabrics, wales direction

Shade Name Ends Bending length

in cm Average

In cm Face UP Face Down

Black 1st 2.15 1.35 1.763

2nd 2.15 1.40

Brown 1st 2.13 1.10 1.64

2nd 2.13 1.20

Red 1st 2.11 1.20 1.615

2nd 2.05 1.10

Table 4

Prewashed dyed fabrics, courses direction


in cm Average


Black 1st 1.15 1.75 1.413

2nd 1.05 1.70

Brown 1st 1.05 1.65 1.375

2nd 1.10 1.70

Red 1st 1.00 1.64 1.33

1st 1.05 1.60



Table 5

Scoured – bleached fabrics, wales direction


in cm Average


Black 1st 2.25 1.80 2.05

2nd 2.25 1.75

Brown 1st 2.15 1.65 1.888

2nd 2.15 1.60

Red 1st 2.25 1.60 1.925

2nd 2.30 1.55

Table 6

Scoured – bleached fabrics, courses direction


in cm

Average

In cm

Face UP Face Down

Black 1st 1.45 1.70 1.60

2nd 1.45 1.80

Brown 1st 1.30 1..60 1.45

2nd 1.35 1.55

Red 1st 1.25 1.50 1.40

2nd 1.35 1.50

From above 3, 4, 5 and 6 tables we studied that prewashed fabrics are softer than

scoured – bleached fabrics due to bending lengths are less in both directions of

prewashed fabrics than scoured – bleached fabrics.

Table 7

Wash fastness to color (ISO105CO6C2S Method)


Shade

Name

Shade

Change

Staining on Multi fibre

N CT CO PA PES PAC WO

Black 5 4.8 4.6 4.5 4.9 4.7 4.8

Brown 4-5 4.7 4.4 4.5 4.7 4.6 4.7

Red 4-5 4.7 4.5 4.5 4.6 4.7 4.8



Table 8

Wash fastness to color test: (ISO105CO6C2S)

Scoured – bleached dyed fabrics

Shade

Name

Shade

Change

Staining on multi fibre

N CT CO PA PES PAC WO

Black 5 4.6 4.5 4.4 4.6 4.6 4.7

Brown 4 4.6 3.8 4.2 4.4 4.5 4.6

Red 4-5 4.7 4.6 4.6 4.7 4.7 4.8

Table 9

Rubbing Fastness test: (ISO / AATCC ) , Grey scale to staining

Prewashed dyed fabrics

Shade name Rubbing GS Value GS Rating

Black Dry 4.85 5

Wet 2.34 2-3

Brown Dry 4.94 5

Wet 4.21 4

Red Dry 4.95 5

Wet 4.22 4

Table 10

Rubbing Fastness test: (ISO / AATCC ) , Grey scale to staining

Scoured – bleached dyed fabrics

Shade Name Rubbing GS Value GS Rating

Black Dry 4.88 5

Wet 2.89 3

Brown Dry 4.95 5

Wet 4.49 4-5

Red Dry 4.96 5

Wet 4.30 4



From tables 7, 8, 9 & 10 we can say that dyeing with reactive dyes on Prewashed &

Scoured – bleached fabrics completed properly that means fixation of reactive dyes on

both fabrics are done fully.

Table 11

Color Strength data: (Spectro photometric)

Prewashed

Standard

Scoured

bleached

Batch

Strength

%

Standard

Strength

%

Batch

CMCDE DL Da Db Dc MI

Black Black 100 91.86 1.61 1.08 -0.13 -0.91 0.91 0.24

Brown Brown 100 85.56 1.16 1.13 -0.99 -0.84 -1.20 0.30

Red Red 100 88.56 1.07 1.47 -0.09 -0.89 -0.20 0.34

From above table it is observed that scoured – bleached batch fabrics are lighter than

prewashed standard fabrics.

RESULTS

Figure 01

Burst Strength

580

600

620

640

660

680

700

720

Black Brown Red

Prewashed kpa

Sc.-bleached kpa



In this figure, it is clearly observed that prewashed fabrics are stronger than scoured –

bleached fabrics .

Figure 02

Bending Length, in cm

In this figure it is clearly seen that prewashed fabrics are softer to scoured – bleached

fabrics.

Figure 03

Wash fastness to color (ISO105CO6C2S Method)


0

0.5

1

1.5

2

2.5

Black

Brown

Red

4.1

4.2

4.3

4.4

4.5

4.6

4.7

4.8

4.9

5

5.1

Black Brown Red

N

CT

CO

PA

PES

PAC

WO



Figure 04

Wash fastness to color( ISO105CO6C2S Method )

Scoured – bleached dyed fabric

From Figure 3 & 5 it is clearly understood that both fabrics are dyed properly with

reactive dyes for deep colors.

Figure 05

Color Strength

0

1

2

3

4

5

6

Black Brown Red

N

CT

CO

PA

PES

PAC

WO

75

80

85

90

95

100

105

Black Brown Red

Standard

, Prewash

Batch , Sc.-

bleached



In this column chart, it is clearly studied that prewashed fabrics need less dye-stuffs

compared to scoured – bleached fabrics to match any shade.

CONCLUSION

In this study, grey cottons were prewashed with oleic acid based product and same time

same fabrics were scoured and bleached with related recipe and after treated Burst

strength were studied, it was observed that the strength of prewashed fabrics are

higher than scoured – bleached fabrics. In this experiment, bending length, wash

fastness to color, rubbing fastness and color strength were observed and it was found

that wash fastness to color and rubbing fastness data are similar, that means both

fabrics were dyed properly. In this study also it was found that color strength values of

prewashed fabrics are higher than scoured and bleached fabrics, it means that

prewashed fabrics need less dye –stuffs to match any shade .There are further scope to

dye many different shades with different percentages on prewashed fabrics. In bulk

production, deep color dyeing required more time than light color dyeing. Prewashed

fabrics required less time to dye deep color compared to scoured–bleached fabrics. So

easily it is possible to deliver more productions with prewashed fabrics. In case of

prewashed fabrics required less softener in finishing stage due to they are already soft.

In the other hand, scoured – bleached fabrics required high amount of softener due to

they are stiff. So it is suggested that same experiment can be done for medium shades.

REFERENCES:

[1] Dr. V. A. Shenai, Technology of Textile Processing, Chemistry of organic textile

chemicals. P.192-196.

[2] Dr. Charles Tomasino, Chemistry & Technology of Fabric Preparation &

Finishing.

[3] Dr. V. A. Shenai, Technology of Textile Processing , volume III, Technology of

Bleaching and Mercerizing P.82, p. 253-285.

[4] Dr. V.A. Shenai, Technology of Textile Processing, volume I, Textile Fibres P. 31-

37.

[5] Textile Progress Published by Taylor & Francies,2006, volume 35 no.4,

Subcription No. 922361905.p.30-50

[6] Dr. V. A. Shenai, Technology of Textile Processing, Volume II, Chemistry of Dyes

and Principles of Dyeing. P.495-557

[7] J.E.Booth,B.Sc.F.T.L, Principles of Textile Testing. p.284-286

[8] B P Saville [8] Physical testing of Textiles. P.154-160,p.204-246

[9] Clariant literature ( Dyes & Chemicals ).

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