Optimization of process parameters for crease resistant...

Indian Journal of Fibre & Textile Research

Vol. 34, December 2009, pp. 359-367

Optimization of process parameters for crease resistant finishing of

cotton fabric using citric acid

T Ramachandrana

Department of Textile Technology, PSG College of Technology, Coimbatore 641 004, India

and

N Gobi, V Rajendran & C B Lakshmikantha

Department of Textile Technology, K S Rangasamy College of Technology, Tiruchengode 637 215, India

Received 18 December 2008; revised received and accepted 20 February 2009

Citric acid has been identified as a successful non-formaldehyde-based crosslinking agent and the process parameters

used for citric acid finishing treatment on cotton fabric optimized. An experiment has been designed using Box and Behnken

method with three levels and their three variables, such as citric acid as a crosslinking agent, trisodiumcitrate as catalyst and

curing temperature. Regression equations have been obtained to analyse fabric properties of 27 combinations and the

optimum process parameters identified. The optimum process parameters are found to be 20% citric acid, 6%

trisodiumcitrate and 180°C curing temperature. It is observed that the high conc. of citric acid increases the crease recovery

angle and reduces the tensile strength of cotton fabric. Trisodiumcitrate acts as very good catalyst at all curing temperatures.

Keywords: Box-Behnken method, Citric acid, Cotton, Crease recovery angle, Crease resistant finishing,

Regression equation

1 Introduction The creasing behavior of cotton fabric is directly

related to the free hydroxyl groups present in the

amorphous regions, which are bound to each other.

To impart crease resistant finish to the cotton

material, the hydrogen bond formation of the

hydroxyl groups should be either masked or totally

removed. The distance of less than 0.5nm is essential

for hydrogen bond formation. In the amorphous

region, the hydroxyl groups of the cellulose polymer

are far apart and hence hydrogen bond formation does

not take place, so these hydroxyl groups remain

unbound.

A popular and widely used method of imparting the

crease resistant finish is the one in which the hydroxyl

groups of adjacent macro molecules are reacted with

bi-functional chemicals1 forming a crosslink with

elimination of water or methanol molecules. For

example, formaldehyde reacts with the two hydroxyl

groups of cellulose, forming the methylene crosslink.

Formaldehyde has many advantages2 as a crosslinking

agent, including low chemical cost and high finish

durability, whereas this process is notorious for lack

of control, high strength loss of treated cotton and

release of excessive fumes in the atmosphere. It was

found that formaldehyde and hydrochloric acid in the

presence of water can form bichloromethyl ether

(BCME), which is a human carcinogen, irritant and

causes allergy to human beings. Hence, crosslinking

process using formaldehyde has been abandoned.

Some of the formaldehyde-based crosslinking agents

are di-methyl urea (DMU) and di-methyl di-hydroxyl

ethylene urea (DMDHEU).

Rowland et al.3 discussed about the poly carboxylic

acids which react readily with cotton at an elevated

temperature. Citric acid has showed higher reactivity

when applied to cotton in the same way. The di-

carboxylic acids are found to be unsuitable for

crosslinking of cellulose to impart enhanced crease

resistance.

A wrinkle resistant cotton fabric was produced by

photo initiated4, free radical reaction with N-methyl

acrylamide monomer from aqueous solution to form a

poly (N-methyl acrylamide) co-polymer, followed by

crosslinking reactions of the methylol groups of the

co-polymer with cellulose.

Cotton fabrics were oxidized with nitrogen

dioxide5 and sodium periodate, and then crosslinked

—————— aTo whom all the correspondence should be addressed.

E-mail: [email protected]

INDIAN J. FIBRE TEXT. RES., DECEMBER 2009

360

with DMU and DMDHEU by the pad-dry-cure

process. The crease recovery angle increases with

degree of oxidation and further, sodium periodate

oxidation causes the release of strain in cellulose

structure, thereby lowering the loss in tensile strength.

Frick and Harper6 studied the dihydroxy imidazol

idimones as one of the crosslinking agents, and found

that these were not economical and much effective.

Some of the recent innovations7 in textile finishing are

concerned with low wet pick-up processes. In these

processes, chemicals such as cellulosic crosslinking

agents were applied onto cotton or polyester/cotton

blend fabrics with wet pick-ups of about 10 - 40%;

fogging was selected for the low wet pick-up method.

Dry crease recovery angle (DCRA) has been

markedly increased by increasing the conc. of

crosslinking agent8 and the best results are obtained

with glyoxal. For glyoxal, the DCRA is found to be

291° and for DMDHEU it is 242°. The whiteness

value of glyoxal is 89%, but it is less than that of

DMDHEU.

Andrews Kottes9 used 7% of citric acid as

crosslinking agent and NaH2PO2 as catalyst. He found

that the increase in percentage conc. of catalyst

increases the whiteness index, durable press rating

(DPR), wrinkle recovery angle and breaking strength.

More than 7% of citric acid reduces the whiteness

index and breaking strength.

Dyeing and finishing of cotton fabric in a single

bath with reactive dye and citric acid10

increases the

colour index value and breaking strength. To measure

the crease recovery of jute fabric, citric acid and

BTCA with different catalysts11

were used with the

maximum curing temperature of 160°C.

Sarkar et al.12

discussed about the dimethylol

dihydroxy ethylene urea based inbuilt catalyst as one

type of formaldehyde crosslinking agents which is

used for bacterial resistance finish on cotton fabrics

using natural herbal extracts. Udomkichdecha et al.13

studied the non-formaldehyde durable press finishing

of cotton fabric with the crosslinking agents such as

acrylic and maleic acid. To analyse the particulate

soiling properties of cellulosic fabrics durable press

finished with polycarboxylic acids like citric acid,

1,2,3,4 butanetetracarboxylicacid (BTCA) was used

as crosslinking agent and sodiumhypophosphite

(SHP) was used as a catalyst for both cases14

. A new

type of catalyst15

named primafin NF was used as a

formaldehyde free crosslinking agent and the results

were compared with DMDHEU treated fabrics.

Sodium dihydrogen phosphate (SDP) and SHP were

used as catalysts for simultaneous dyeing and

finishing of cotton fabric using reactive dyes and

citric acid as a crosslinking agent16

.

In the present study, an attempt has been made to

find out the optimum processing parameters used for

citric acid finishing treatment on cotton fabric with

the help of Box and Behnken method.

2 Materials and Methods 2.1 Materials

A bleached and mercerized 100% cotton fabric,

having the specifications plain weave, 40s Ne count

yarn (warp × weft), 53 ends/cm, 25 picks/cm and

120 gsm weight, was used for the study. Crosslinking

agent citric acid, catalyst trisodiumcitrate, wetting

agent Lissopal-N and softening agent silicone

emulsion were used to impart crease resistant finish to

the fabric.

2.2 Methods

To optimize the process parameters, experimental

plan was designed using Box-Behnken method. In

this experimental plan, three levels and their three

variables were selected (Table 1).

The fabric was pretreated in a solution containing

1% HCl for the period of 1 h at room temperature

with the material-to-liquor ratio of 1:10. The

pretreated and dried fabric was padded in a solution

containing citric acid, trisodiumcitrate, wetting agent

(0.1%) and softener (1%), and the wet pick-up was

maintained at 100% (owf).

The padded fabric was dried at 80oC and then the

curing process was carried out at 160°C, 180°C and

200°C for 2 min. The cured fabric was treated with

soap solution (sodium lauryl sulphate 2 gpl) for

5 min, rinsed for 10 min at room temperature and then

dried. Based on the Box and Behnken method, fifteen

trials were conducted (Table 2).

The physical properties of treated and untreated

fabrics were tested by standard testing equipments

and the results are given in Table 2. Shirley crease

recovery tester was used to measure the crease

recovery angle as per ASTM D-1296; electronic

Table 1 Details of process parameters and different levels for

crease recovery finish

Process parameter Different levels

-1 0 +1

Citric acid conc. (X1), % (owf) 10 15 20

Trisodiumcitrate conc. (X2), % (owf) 4 5 6

Curing temp. (X3),°C 160 180 200

RAMACHANDRAN et al.: CREASE RESISTANT FINISHING OF COTTON FABRIC

361

tensile strength tester to measure the tensile strength

of fabric as per ASTM D-5035; Elmendorf tearing

strength tester to measure the tear strength of fabric as

per ASTM D-1424-96; Martindale abrasion tester to

measure the weight loss of cotton fabric due to

abrasion as per ASTM D-4966; vertical strip test

method to analyze the wicking behavior of fabric;

Shirley air permeability tester to measure the air

permeability of fabric as per ASTM D 737-99;

Shirley stiffness tester to measure the flexural rigidity

of the fabric as per ASTM D 1388; and

spectrophotometer (data color) to measure the

whiteness index of fabric as per ASTM DE 313-67.

2.3 Statistical Analysis

Box and Behnken method has been adopted to

formulate the experimental design, in which fifteen

different combinations are formed. This method also

offers the advantage of being rotatable which means

that the fitted model estimates the response with equal

precision at all points in the factor space that are

equidistant from the centre.

A quadratic polynomial was used to analyze the

relationship of each response with the three

independent variables, as given below:

jiij

3

1i

2iii

3

i

1iii

3

1i0 xxbxbxbbY

j

∑∑∑=

<

==

+++=

where b0, bi, bii and bij are the coefficients of the

regression equations; i and j, the integers; and Y, the

response of the dependent variable.

3 Results and Discussion

3.1 Physical Properties

Table 2 shows the various physical properties of

cotton fabric treated with citric acid as crosslinking

agent in the presence of trisodiumcitrate as catalyst at

different curing temperatures. The regression

equations for the various properties are given in

Table 3. It is found that the tensile strength (Y1), tear

strength (Y3), wicking (Y4), crease recovery angle

(CRA) (Y6) and flexural rigidity (Y7) are dependent

on second order polynomial equation. The properties,

such as abrasion resistance (Y2) and air permeability

(Y5), show only linear and interaction or combined

effects on the process variables.

Based on the best fit regression equations, the

values of the physical properties of 27 possible

combinations are calculated (Table 4). For the

Table 2 Physical properties of untreated and treated samples using different process parameters

Process parameters Properties

Sample code

Conc. of

citric acid

%

Conc. of

trisodiumcitrate

%

Temperature

°C

Tensile

strength

kg

Weight

loss

%

Tear

strength

g

Wicking

%

Air

permeability

cc/cm2/s

CRA

(w+f)

deg

Whiteness

index

Over all

flexural

rigidity

mg/cm

Untreated(U1) - - - 86.2 3.62 1184 29.33 27.79 88.10 140.20 1882.30

Treated

T1

10

4

180

83.6

5.30

1192

22.63

26.90

135.80

125.67

2145.33

T2 20 4 180 67.4 7.08 736 25.00 27.46 144.40 126.08 2128.95

T3 15 4 200 59.1 5.76 744 25.98 23.20 133.00 132.25 1675.52

T4 15 4 160 52.3 6.43 808 32.28 27.66 133.40 131.63 1468.16

T5 20 5 200 60.4 4.40 816 26.96 26.26 143.60 121.63 2388.36

T6 10 5 200 67.5 3.62 1024 26.77 27.83 130.00 122.79 2402.10

T7 20 5 160 61.3 4.10 1072 24.01 30.13 139.40 126.39 1951.37

T8 10 5 160 64.8 5.02 1064 24.80 29.25 131.40 132.30 2551.73

T9 15 6 160 54.2 3.81 1180 21.06 28.67 140.80 130.17 2132.86

T10 15 6 200 75.9 6.76 1120 20.86 28.93 142.00 109.97 1665.38

T11 20 6 180 63.9 4.27 1105 25.78 29.81 145.20 136.30 1745.04

T12 10 6 180 70.2 3.80 1098 20.47 27.85 134.60 126.91 2889.39

T13 15 5 180 74.9 4.17 1156 22.24 28.74 133.97 129.27 3257.32

T14 15 5 180 73.8 4.99 1132 20.66 28.63 133.60 128.75 3071.63

T15 15 5 180 67.6 5.70 1099 21.06 29.12 132.40 127.95 3029.59


362

purpose of optimization, the properties such as crease

recovery angle, whiteness index, tensile strength and

tear strength are given in Table 5 with respect to the

ascending order of CRA for 10 samples.

3.2 Influence of Process Parameters on Crease

Recovery Angle

Influence of process parameters on crease recovery

angle have been elaborately discussed in three

Table 3 Regression equations for various properties

Property Regression equation R R2 F-ratio

Tensile strength, kg Y= -7.193 X1 -68.774 X2 +3.176 X3 +0.067X12 +0.076X2

2 -0.013X32

+0.644X1X2 +0.006X1X3 +0.324X2X3 0.994 0.586 110.42

Weight loss, % Y= 0.821X1 -0.089X2-0.009X3 -0.118X1X2-0.001X1X3+0.007X2X3 0.968 0.297 45.74

Tear strength, g Y= -61.106X1-250.428X2 +24.894X3 -0.885X12-36.854X2

2-

0.093X32+25.307X1X2-0.309X1X3+2.018X2X3

0.996 0.826 191.5

Wicking, % Y= 0.189X1 +3.616X2+0.183X3 +0.038X12-0.486X2

2 +0.000X32 +0.050X1X2

+0.008X1X3 -0.009X2X3 0.988 0.289 56.64

Air permeability

cc/ cm2/s

Y= 2.449X1 +0.299X2+0.1113X3-0.003X1X2-0.013X1X3+0.006X2X3 0.999 0.630 1112.3

Crease recovery, deg Y= -3.080X1 -23.029X2+2.220X3 +0.092X12+3.006X2

2-

0.006X32+0.020X1X2+0.007X1X3-0.029X2X3

1.000 0.814 2679

Flexural rigidity

mg/cm

Y= -444.386X1 +4.581.389X2-56.831X3-0.987X12-520.696X2

2-0.088X32-

36.317X1X2+3.373X1X3+7.018X2X3 0.974 0.515 251.7

Whiteness index Y= -5.770X1 +24.793X2 +1.465X3 +0.016X12+0.821X2

2-

0.002X32+0.514X1X2+0.015X1X3-0.235X2X3

0.999 0.613 749.45

Table 4 Calculated values of response for various process parameters

Process parameters Properties

Sample

No.

Citric

acid

conc.

%

Trisodiumcitrate

conc., %

Temperature

°C

Tensile

strength

kg

Weight

loss

%

Tear

strength

g

Wicking

%

Air

permeability

cc/cm2/s

CRA

(w+f)

deg

Whiteness

index

Over all

flexural

rigidity

mg /cm

1 10 4 180 81.21 4.75 1085.82 26.43 26.186 132.10 133.46 1468

2 20 4 180 65.94 6.44 665.34 27.32 27.156 142.30 128.12 1580

3 15 4 200 64.34 5.67 757.52 26.47 25.471 133.48 130.19 1446

4 15 4 160 69.06 5.51 963.48 25.39 27.871 131.52 128.99 1532

5 20 5 200 68.57 5.37 821.89 25.51 26.025 140.20 124.89 1455

6 10 5 200 76.20 5.06 1051.1 25.72 27.685 128.40 122.09 1580

7 20 5 160 59.13 5.13 1008.9 26.39 30.785 138.00 130.09 1711

8 10 5 160 69.16 4.42 1114.54 23.40 27.245 129.00 133.29 1476

9 15 6 160 56.03 4.04 1130.52 21.52 30.159 136.90 135.22 1700

10 15 6 200 77.23 4.76 1086.00 21.88 28.239 136.54 117.62 1633

11 20 6 180 72.31 4.06 1166.16 23.60 29.654 146.72 130.09 1701

12 10 6 180 74.70 4.73 1080.50 21.71 28.744 136.12 125.15 1704

13 15 5 180 71.79 5.00 1058.44 24.30 27.935 134.00 127.99 1528

14 10 5 180 77.88 4.74 1120.02 24.56 27.465 131.10 128.49 1532

15 20 5 180 69.05 5.25 952.61 25.95 28.405 141.50 128.29 1587

16 15 4 180 71.90 5.59 897.70 25.93 26.671 134.90 130.39 1493

17 15 6 180 71.83 4.40 1145.46 21.70 29.199 139.12 127.22 1671

18 10 4 160 78.97 4.57 1120.70 25.09 26.086 129.42 133.56 1417

19 20 4 160 62.50 6.46 762.02 27.58 29.656 138.22 125.22 1709

20 15 5 160 62.47 4.78 1083.86 23.94 29.015 131.20 131.29 1562

21 10 4 200 73.05 4.93 976.54 27.77 26.286 129.98 131.76 1511

22 20 4 200 58.98 6.42 494.26 27.06 24.656 141.58 129.42 1444

23 15 5 200 70.71 5.22 958.62 24.66 26.855 132.00 123.09 1486

24 20 6 160 55.91 3.80 1075.80 24.22 31.914 143.80 136.59 1820

25 10 6 160 59.50 4.27 1034.66 20.73 28.404 134.60 134.65 1643

26 10 6 200 79.50 5.19 1051.94 22.69 29.084 132.84 114.05 1756

27 20 6 200 78.31 4.32 1045.23 22.98 27.394 144.84 121.99 1573


363

combinations of process parameters such as influence

of citric acid and trisodiumcitrate, influence of citric

acid and temperature and influence of trisodiumcitrate

and temperature.

3.2.1 Influence of Citric Acid and Trisodiumcitrate

Figure 1 (a) shows the influence of citric acid and

trisodiumcitrate on crease recovery angle. Initially the

crease recovery angle is less with low conc. of

chemicals. Crease recovery angle decreases with the

increase in trisodiumcitrate conc. at the same conc. of

citric acid. Then, the CRA gradually increases with

the increase in conc. of citric acid.

3.2.2 Influence of Citric Acid and Temperature

Figure 1(b) shows the influence of citric acid and

temperature on crease recovery angle. The increase in

citric acid conc. and curing temperature directly

increases the crease recovery angle. But the maximum

conc. of citric acid and lower curing temperature

show lower crease recovery angle and vice-versa.

3.2.3 Influence of Trisodiumcitrate and Temperature

Figure 1(c) shows the influence of trisodiumcitrate

and temperature on crease recovery angle. The low

conc. of trisodiumcitrate and different levels of curing

temperatures show high crease recovery angle.

Gradual increase in conc. of trisodiumcitrate reduces

the crease recovery angle and after increasing

5% conc. of trisodiumcitrate, again it gradually

increases. At high curing temperature and high conc.

of trisodiumcitrate, the best results are obtained than

at low curing temperature with high conc. of

trisodiumcitrate.

The crease recovery angle of woven cotton fabric

for different combinations is given in Table 4. It

shows that the crease recovery angle is high (146.72°)

when the fabric is treated with the high conc. of citric

acid (20%) as a crosslinking agent and trisodium

citrate (6%) as a catalyst. The variation in curing

temperature also shows the significant difference in

the crease recovery angle. A combination of low

curing temperature (160°C) and high citric acid conc.

(20%) shows significant change in crease recovery

angle. The curing temperature of 180°C shows the

best result than the other two levels.

The results show that the crease recovery angle of

cotton fabric is increased by increasing the conc. of

Table 5 — Process parameters and other properties for cases having higher CRA

Sample

No.

Citric acid

conc., %

Trisodiumcitrate

conc., %

Temperature

°C

CRA (w+f)

deg

Whiteness

index

Tensile

strength, kg

Tear strength

g

1 20 6 180 146.72 130.09 72.31 1166.168

2 20 6 200 144.84 121.99 78.31 1045.230

3 20 6 160 143.80 136.59 55.91 1075.808

4 20 4 180 142.30 128.12 65.94 665.344

5 20 4 200 141.58 129.42 58.98 494.264

6 20 5 180 141.50 128.29 69.05 952.61

7 20 5 200 140.20 124.89 68.57 821.89

8 15 6 180 139.12 127.22 71.83 1145.463

9 20 4 160 138.22 125.22 62.50 762.024

10 20 5 160 138.00 130.09 59.13 1008.93

Fig. 1 Influence of (a) citric acid and trisodium citrate, (b) citric acid and temperature, and (c) trisodium citrate and temperature on

crease recovery angle


364

citric acid and curing temperature and the

trisodiumcitrate acts as the best catalyst at all conc. of

citric acid and curing temperature. The average value

of increase in crease recovery angle is more than

50%, whereas it is around 30% in the case of existing

DMDHEU treatment13

.

3.3 Influence of Process Parameters on Whiteness Index

Influence of process parameters on whiteness index

has been elaborately discussed in three combinations

of process parameters, such as influence of citric acid

and trisodiumcitrate, influence of citric acid and

temperature and influence of trisodiumcitrate and

temperature.



trisodiumcitrate on whiteness index. The low conc. of

citric acid and trisodiumcitrate gives higher whiteness

index value. However, low conc. of citric acid and

high conc. of trisodiumcitrate give maximum value of

whiteness index. High conc. of citric acid and

trisodiumcitrate reduces the whiteness index. From

this, it is evident that the conc. of citric acid decides

the whiteness index.


Figure 2 (b) shows the influence of citric acid and

temperature on whiteness index. It is apparent that

low conc. of citric acid and curing temperature shows

good whiteness index, whereas high curing

temperature with low conc. of citric acid reduces the

whiteness index.

The whiteness is slightly increased while

increasing the conc. of citric acid and curing

temperature. It is found that 180°C is the optimum

curing temperature, where the whiteness index is

maximum. Any further increase in the curing

temperature has resulted in drastic reduction of

whiteness index. High conc. of citric acid and high

curing temperature drastically reduce the whiteness

index.


Figure 2 (c) shows the influence of trisodiumcitrate

and temperature on whiteness index. It is clear that

there is a linear relationship between trisodiumcitrate

and whiteness index. Low conc. of trisodiumcitrate

with high curing temperature gives good whiteness as

against high conc. of trisodiumcitrate and low curing

temperature that does not affect the whiteness. Hence,

the change in whiteness is mainly due to the curing

temperature.

Table 4 shows that the whiteness index of the

cotton fabric is not affected by the catalyst and it is

inversely proportional to the citric acid conc. and

curing temperature. Low conc. of citric acid (10%)

Fig. 2 Influence of (a) citric acid and trisodium citrate, (b) citric

acid and temperature, and (c) trisodium citrate and temperature on

whiteness index


365

and low curing temperature (160°C) at different levels

of trisodiumcitrate show the insignificant effect on

whiteness of cotton fabric. The whiteness index of

cotton fabric treated with 15% citric acid and 6%

trisodiumcitrate at 180°C curing temperature show

more than 90% retention and it is greater than that of

other conventional crosslinking agents8.

3.4 Influence of Process Parameters on Tensile Strength

Influence of process parameters on tensile strength

has been elaborately discussed in three combinations

of process parameters such as influence of citric acid

and trisodiumcitrate, influence of citric acid and


temperature. 3.4.1 Influence of Citric Acid and Trisodiumcitrate


trisodiumcitrate on tensile strength. The tensile

strength of treated fabric gradually reduces as the

conc. of citric acid increases. The influence of

trisodiumcitrate is insignificant even at high conc. of

citric acid, whereas low conc. of citric acid and

trisodiumcitrate gives high tensile strength.

At low conc. of citric acid and high conc. of

trisodiumcitrate, there is moderate strength retention.

It shows that the crosslinking reaction is activated and

bond formation has been increased while increasing

the conc. of trisodiumcitrate.



temperature on tensile strength. With the increase in

curing temperature and at low conc. of citric acid,

there is a gradual increase in tensile strength which

reaches the maximum value (180°C), and beyond

180°C the tensile strength gradually comes down. The

formation of crosslinks is responsible for the

reduction in tensile strength of the fabric.

High conc. of citric acid with gradual increase in

temperature up to 180°C also increases the tensile

strength of the fabric. At the same time, a gradual

reduction is noticed beyond 180°C. This reduction in

tensile strength is due to the release of hydrochloric

acid and the hydrolysis of cellulose. The structural

damage of cotton fabric is moderate at low conc. of

citric acid for all levels of curing temperature. 3.4.3 Influence of Trisodiumcitrate and Temperature


and temperature on tensile strength. The effect

of trisodiumcitrate on tensile strength is insignificant.

The increase in curing temperature upto 180°C

gradually increases the tensile strength at different

conc. of trisodiumcitrate. At the same time, there is no



tensile strength


366

significant change in tensile strength. The influence of

trisodiumcitrate conc. on tensile strength is

insignificant.

Table 4 shows the interactive or combined effect of

the variables on tensile strength of the fabric. Lower

conc. of citric acid (10%) and trisodiumcitrate (4%)

with optimum curing temperature of 180°C gives

higher tensile strength (81.21 kg). Hence, 4% of

trisodiumcitrate is enough to obtain maximum crease

recovery angle and tensile strength. The average

tensile strength retention is found to be approximately

80%, which is similar to that observed by

conventional DMDHEU treatment13

.

3.5 Influence of Process Parameters on Tear Strength

Influence of process parameters on tear strength

have been elaborately discussed in three combinations

of process parameters such as influence of citric

acid and trisodiumcitrate, influence of citric acid and


temperature.


Figure 4(a) shows the influence of citric acid and

trisodiumcitrate on tear strength. The tear strength of

fabric is proportionately increased by the increase in

conc. of citric acid and trisodiumcitrate.



temperature on tear strength. The tear strength of

fabric is gradually increased up to the optimum curing

temperature of 180°C and reduces thereafter. High

conc. of citric acid and curing temperature reduce the

tear strength as observed for tensile strength.



and temperature on tear strength. Low curing

temperature with different levels of trisodiumcitrate

do not affect the tear strength. At optimum

temperature (180°C), the strength retention is more

but high curing temperature reduces the tear strength

drastically.

It is observed from Table 4 that the tear strength of

cotton woven fabric is not affected by the

trisodiumcitrate and that it is inversely proportional to

the conc. of citric acid and curing temperature. Higher

curing temperature (200°C) and higher citric acid

conc. (20%) significantly reduce the tear strength of

fabric. The tear strength retention of fabric is around

90%, whereas in the case of DMDHEU treatment it is

around 80% (ref. 15)

Table 4 shows the effect of process parameters on

different properties. Air permeability, wicking

behavior, abrasion and flexural rigidity show

insignificant effect with respect to various process



tear strength


367

parameters. The objective of the study is to obtain the

maximum crease recovery angle of fabric with

optimum values for tensile strength, whiteness index

and tearing strength. Based on the values of crease

recovery angle the variables are sorted out in Table 5.

It is observed that the optimized process parameters

are 20% citric acid conc.; 6% trisodiumcitrate conc.;

and 180°C curing temperature in order to obtain better

properties of the fabric.

4 Conclusions Citric acid is found to be one of the most effective

crosslinking agents for crease resistant finish. High

conc. of citric acid and trisodiumcitrate shows excellent

crease resistance, whereas at higher conc. of citric acid

the whiteness index reduces. The optimum curing

temperature of 180°C gives best crease recovery angle.

At 160°C curing temperature and 4% citric acid with

different levels of trisodiumcitrate, better whiteness

index is obtained. Hence, the whiteness index of fabric

is not affected by the catalyst. Tear strength of the

fabric is also not affected by the trisodiumcitrate.

Hence, trisodiumcitrate is one of the best catalysts to

reduce the yellowness which is given by citric acid and

also it gives good tear strength retention. High curing

temperature and high conc. of chemicals reduce the

tensile strength drastically. The tensile strength

retention is around 90% at 180°C curing temperature.

Lower curing temperatures, 15% of citric acid and 5%

of trisodiumcitrate show good abrasion resistance.

Wicking and air permeability values are found to be

insignificant with respect to process parameters. It is

concluded that 20% of citric acid, 6% of

trisodiumcitrate and 180°C curing temperature are the

optimized process parameters to achieve better fabric

properties.

Industrial Importance: The study suggests the

combination of process parameters to obtain

optimized fabric properties with reduced cost of the

process.

Acknowledgement The authors are thankful to the Principal and

management of the PSG College of Technology, K S

Rangasamy College of Technology, and to the

Defence Research and Development Organisation

(DRDO), New Delhi, for providing the

financial support to carry out this project

(ERIP/ER/0604354/M01/991 dt. 10.08.2007).

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