Dimensional stabilization of cotton plain weft knitted fabric using mercerization treatment

Fibers and Polymers 2009, Vol.10, No.6, 847-854

847

Dimensional Stabilization of Cotton Plain Weft Knitted Fabric

Using Mercerization Treatment

A. R. Moghassem* and M. R. Bakhshi

Faculty of Engineering, Textile Engineering Group, Islamic Azad University, Qaemshahr Branch, 163, Iran

(Received June 26, 2008; Revised October 18, 2009; Accepted November 3, 2009)

Abstract: Investigation on dimensional stability of cotton plain weft knitted fabric manufactured from rotor spun yarn, sub-jected to mercerization treatment has been represented. Several fabric samples were mercerized considering variation in timeof treatment, bath temperature, concentration of alkali solution and also mercerizing tension. Values of constant of course(K

c), constant of wale (K

w), the area geometry constant (K

s) which are indicative of fabric dimensional stability were calcu-

lated after treatment for mercerized samples. Then, these values were compared with those of un-treated samples subjected todry and wet relaxation and also were compared with each other. Based on the effect of each variable itself and their simulta-neous effect, it was concluded that, mercerization treatment and considered parameters had a distinctive influence on dimen-sional stability of the fabric. Mercerized samples had better dimensional stability in comparison with un-treated ones. Acomprehensive experimental analysis showed that, there is meaningful difference between K

s values of the samples mercer-

ized at various conditions. Also, the area geometry constant (Ks) achieved after treatment was higher than that of other relax-

ation methods.

Keywords: Plain weft knitted fabric, Dimensional stability, Mercerization treatment, Relaxation treatment, Area geometry

constant

Introduction

Relationship between loop length and dimensional stability

of plain weft knitted fabric has been studied with respect to

the leaf theory. When a fabric reaches the fully relaxed state,

the minimum amount of energy is generated in its structure

[1]. Similarly a deformed structure tends to get minimum

energy state in which internal forces and couples are in

mechanical equilibrium [2]. However, there is not any

dependence between final shape of the loop and physical

properties of the yarn in these conditions [1].

In addition to the fully relaxed state, two other relaxation

states i.e. dry and wet have been defined for knitted fabric [1].

Studies have shown that, different fibers react in different

ways to these treatments, so that, the equilibrium values of

the geometry constant vary [3].

Different models of loop theory have been assumed on

physical and geometric structure of plain knitted fabric and

many practical investigations have carried out in this regard

[4-7]. Some of the findings were fairly close to the results of

experimental works while others did not show a close

correspondence [8,9]. However, modeling dimensional

properties of plain weft knitted fabric showed that, the

theoretical Ks value (25.986) was higher than the experimental

value for fully relaxed plain weft knitted fabric [10,11].

Since the theoretical Ks value is higher than the

experimental value for fully relaxed fabric, more suitable

relaxation methods should be used in finishing treatment to

raise the practical Ks value, and to achieve the ideal

theoretical state. Among various chemical treatments that

are in existence to improve fabric performance, mercerization

is of major interest to the researchers. Extensive knowledge

and experience on this subject already exists [12-14].

Based on the literature, time of treatment, bath temperature,

concentration of alkali solution, and mercerizing tension are

four main factors in mercerization treatment [15]. The

effects of these factors on the properties of woven fabrics

have been studied by researchers. Previous study showed

that, increasing mercerizing tension leads to the more

tenacity of the product due to improvement in degree of

mercerization. By increasing the tension ratio, tenacity

increases but, there will be a decline in strain [16,17].

However, strong brightness is only achieved under tension.

Highest brightness values are obtained when the shrinkage is

reduced to 0 % but, in this condition the dye-ability of the

product decreases [15].

Concentration of the alkali solution evaluates the number

of alkali substance’s hydrate groups, penetration of the

solution into the fiber and therefore the swelling degree [16].

Temperature has an effect on swelling event. By decreasing

the temperature, the velocity of penetration in the fiber

decreases because of the higher viscosity of the solution [15].

In the present work, mercerization treatment is suggested

for stabilization of cotton weft knitted fabric due to lack of

references for the effects of the process on the properties of

that fabric. The aim of the recent study is increasing

dimensional stability of the fabric using mercerization

treatment instead of other conventional and modern

relaxation methods, study on the effect of bath parameters

on dimensional stability and also introducing mercerization

condition in which the best result (more Ks) is achieved.

Therefore knitted fabric were mercerized considering*Corresponding author: [email protected]

DOI 10.1007/s12221-009-0847-5

848 Fibers and Polymers 2009, Vol.10, No.6 A. R. Moghassem and M. R. Bakhshi

variation in time of treatment, concentration of alkali

solution, bath temperature, and also time of treatment. After

treatment the area geometry constant of the samples were

calculated. These values were compared with those of un-

treated samples subjected to dry and wet relaxation and with

each other.

Materials and Methods

The fabric studied was knitted on a Piylong circular

knitting machine (gauge 24 and diameter 30 inch) with

positive yarn feed. It was of 20/1 (Ne) rotor cotton yarn with

turns per meter of 875. Plain weft knitted fabric was

produced with the loop length of 0.294 cm.

Knitted fabric was divided in 26 samples. Two samples

were used for obtaining values of constant dimensional

parameters in wet and dry relaxation states and others were

treated with alkali solution as mercerized fabrics.

In first part of the experiments, six observations with

dimensions of 40 cm×40 cm were taken from each sample.

In the middle of each fabric (156 observations), two square

of 35 cm×35 cm and also 25 cm×25 cm were measured by

means of a template and marked by five points in length

(wale direction) and width (course direction) directions by a

black permanent marker, so that during the mercerization

treatment these marks still remain. Then, mentioned samples

were subjected to the following relaxation treatments [18].

Dry relaxation state; Fabric samples were placed on a flat

surface at room conditions for 24 h after coming out of the

machine to release knitted stresses [18].

Wet relaxation state; Fabric samples were placed in water

at 40o

C for 24 h, rinsed gently by hand and dried on a flat

surface for 24 h at room conditions [18].

Mercerization treatment; After preparing 144 fabric

observations according to the above conditions, some

wooden frames with dimensions of 40 cm×40 cm were

made. Dimensions of the frames were calculated with

respect to the marked dimensions of the fabrics (35 cm×

35 cm) and mercerizing tension according to equation (1)

and Figure 1.

D.W.F=((M.T %+ 100)×35) / 100 (1)

Where:

D.W.F is dimensions of the wooden frame (cm); M.T is

mercerizing tension (%)

Then fabric samples were drawn equally and uniformly in

both course direction and wale direction till marked line

35 cm×35 cm on the fabrics was reached to the dimensions

of (36.75×36.75 cm) or (40.25×40.25 cm) and was fitted to

the line 1 on the frame (Figure 1). Then sample was fixed on

this new position by staples.

Fabric samples were placed in a mercerization bath

respectively. Variation in concentration of alkali solution

(NaoH 99 %), bath temperature, mercerization tension and

also time of treatment were considered during processing.

Specifications of the prepared samples have been shown in

Table 1. After timing, in order to rinsing and neutralization,

fabric sample fixed on the frame was put in water with

Figure 1. A schematic of wooden frame used to fix samples in

mercerization treatment; (1) Line (36.75 cm×36.75 cm) or (40.25 cm

×40.25 cm) marked on the frame to fix samples after applying

mercerization tension and (2) Border lines of the frame.

Table 1. Experimental plan and specifications of the samples

Sample

no.

Specifications of mercerization bath

Temperature

(oC)

Time

(sec)

Concentration

of alkali

solution (gr/lit)

Mercerizing

tension

(%)

1 20 120 200 5

2 20 120 200 15

3 20 240 200 5

4 20 240 200 15

5 40 120 200 5

6 40 120 200 15

7 40 240 200 5

8 40 240 200 15

9 60 120 200 5

10 60 120 200 15

11 60 240 200 5

12 60 240 200 15

13 20 120 300 5

14 20 120 300 15

15 20 240 300 5

16 20 240 300 15

17 40 120 300 5

18 40 120 300 15

19 40 240 300 5

20 40 240 300 15

21 60 120 300 5

22 60 120 300 15

23 60 240 300 5

24 60 240 300 15

25 Dry relaxation

26 Wet relaxation

Dimensional Stabilization of Cotton Plain Weft Knitted Fabric Fibers and Polymers 2009, Vol.10, No.6 849

temperature of 60 oC and then sample was neutralized in a

bath containing Acetic acid 2 % for 4 min.

At next step, fabric sample was rinsed in warm water.

Sample was drained in cold water after removing from the

wooden frame and then was dried for 24 h on a flat surface

at room conditions. Due to change in concentration of alkali

solution in the bath, contains of the bath was replaced with

the new solution after 3 treatments. Consequently, 24 fabric

samples and 6 observations in each sample were mercerized

according to the mentioned conditions. Shrinkage or change

in length (wale direction) and width (course direction) of all

the samples after each different relaxation status was

measured (equation (2)) at the area with dimensions of

25 cm×25 cm marked by marker on the samples.

S = ((L1−L2) /L1)×100 (2)

Where:

S is change in length (wale) or width (course) direction of

the fabric after treatment; L1 is dimensions of the sample

before relaxation treatment (25 cm); L2 is dimensions of the

sample after relaxation treatment measured by ruler (cm).

The course and the wale of all the samples were counted at

the 25 cm×25 cm dimension of the fabric marked previously

in all relaxed states. Then, numbers of courses per

centimeter (CPC), numbers of wales per centimeter (WPC)

and stitch density (SD) of all fabric samples were calculated.

The numerical values of constant geometry were calculated

according to Munden’s equations (3) [1] and the results are

shown in Table 2. Statistical analysis was carried out to

analyze the differences between test results for different

groups of samples in 5% level of significance.

CPC = Kc/L WPC = K

w/L SD = K

s/L

2 (3)

Where:

L is the length of the loop; Kc, K

w, K

s are the constants

termed fabric dimensional parameters; CPC is the courses

per centimeters; WPC is the wales per centimeter; SD is the

number of loops per square centimeter.

Results and Discussion

At first part of the research, the effects of each factor itself

Table 2. Values of constants termed dimensional parameters of the samples at different relaxation states

Sample no. Shrinkage (%)

Kc

Kw

Ks

CPC WPC SDC. D W. D

1 14.00 10.00 6.12 3.28 20.10 20.85 11.15 238.57

2 12.00 4.00 5.57 3.28 18.25 18.93 11.15 223.88

3 14.00 6.00 6.05 3.56 21.56 20.57 12.10 249.45

4 14.00 8.80 5.17 3.32 17.15 17.58 11.29 209.99

5 21.20 8.00 6.52 3.70 24.16 22.17 12.60 279.53

6 20.00 6.40 6.03 3.63 21.88 20.51 12.34 252.92

7 18.80 13.20 5.98 4.16 24.88 20.34 14.51 287.86

8 16.00 4.60 6.37 3.44 21.92 21.66 11.70 253.84

9 18.00 10.00 6.75 3.61 24.37 22.96 12.27 277.27

10 13.20 7.20 5.83 3.71 21.62 19.82 12.61 275.02

11 17.20 16.60 6.80 3.55 24.14 23.15 12.09 279.99

12 20.80 7.20 6.27 3.62 22.71 21.33 12.31 251.18

13 20.40 7.20 6.20 3.50 21.70 21.08 11.90 252.45

14 16.00 10.40 6.44 3.31 21.50 21.90 11.25 248.75

15 24.00 8.00 6.29 3.55 22.43 21.39 12.07 259.51

16 24.00 8.00 6.20 3.72 23.11 21.08 12.65 269.23

17 22.40 10.80 6.12 3.76 23.04 20.74 12.78 267.15

18 20.00 10.00 6.10 3.53 21.53 20.74 12.00 249.45

19 22.00 12.00 6.17 3.73 23.07 20.98 12.68 266.92

20 19.60 11.20 6.15 3.68 22.74 20.91 12.51 263.10

21 20.80 14.00 6.66 3.41 22.76 22.65 11.59 265.87

22 14.00 10.60 6.33 3.41 21.59 21.15 11.59 248.75

23 18.80 7.60 6.17 3.62 22.32 21.08 12.31 258.93

24 10.40 3.60 5.96 3.23 19.19 20.27 10.98 222.26

Dry relaxed 18.40 7.60 5.85 3.00 17.55 19.89 10.20 203.63

Wet relaxed 10.40 3.60 5.69 3.22 18.32 19.35 10.95 212.65

C.D: width direction (course direction), W.D: length direction (wale direction).


on dimensional stability of plain weft knitted fabric (Ks

value) were investigated. In this case, one parameter was

selected as a variable and the rest of the parameters were

chosen as constants. Fabric samples were compared for

studying the effect of mercerizing parameters on dimensional

stability according to Table 3. In this part of the work,

statistical analysis was employed (Univariat from General

Linear Model in SPSS 16 software) to assess the statistical

meaning of the main effect of mercerization variables and

their interaction on Ks value. This analysis helps authors

justify findings of the research. The results of the analysis

have been shown in Table 4.

Effect of Mercerizing Tension

Results showed that, dimensional stability of the samples

(Ks value) was decreased with increase in mercerization

tension probably due to improvement in orientation of

molecular chains along fiber axes. This leads to decrease in

penetration of alkali solution into the fiber structure and

hence decreases fiber swelling and consequently Ks values

as can be seen in Figure 2. Decrease in Ks

value due to

increase in mercerizing tension was clear in fabric samples

mercerized in alkali concentration of 200 g/lit and temperature

of 20 oC.

Figure 2 shows the effect of mercerization tension on the

Ks value for various samples. Paired t test was employed in

order to compare Ks value of the samples in each group that

Table 3. Comparing fabric samples in order to study the effect of mercerizing parameters on dimensional stability (Ks) based on the sample

code (Figures 2-5)

Grouping fabric samples in order to compare them for the effect of mercerizing tension on Ks (groups 1-12)

1-2 3-4 5-6 7-8 9-10 11-12

13-14 15-16 17-18 19-20 21-22 23-24

Grouping fabric samples in order to compare them for the effect of concentration of alkali on Ks (groups 1-12)

1-13 2-14 3-15 4-16 5-17 6-18

7-19 8-20 9-21 10-22 11-23 12-24

Grouping fabric samples in order to compare them for the effect of time of treatment on Ks (groups 1-12)

1-3 2-4 5-7 6-8 9-11 10-12

13-15 14-16 17-19 18-20 21-23 22-24

Grouping fabric samples in order to compare them for the effect of bath temperature on Ks (groups 1-8)

1-5-9 2-6-10 3-7-11 4-8-12

13-17-21 14-18-22 15-19-23 16-20-24

Table 4. Results of the Univariat statistical analysis to show main

effect of the mercerization variables and their interaction on

dimensional stability of the samples (Ks)

Tests of between-subjects effects

Dependent variable: Ks

Source

Type III

sum of

squares

dfMean

squareF Sig.

Corrected model 475.134a 23 20.658 118.417 .000

Intercept 69534.174 1 69534.174 3.986E5 .000

CAS 1.904 1 1.904 10.917 .001

BT 117.207 2 58.603 335.929 .000

TT 2.102 1 2.102 12.052 .001

MT 120.158 1 120.158 688.777 .000

CAS*BT 140.689 2 70.344 403.232 .000

CAS*TT .553 1 .553 3.167 .078

CAS*MT 28.214 1 28.214 161.729 .000

BT*TT 9.528 2 4.764 27.309 .000

BT*MT 2.926 2 1.463 8.387 .000

TT*MT .748 1 .748 4.289 .041

CAS*BT*TT 12.902 2 6.451 36.978 .000

CAS*BT*MT 17.423 2 8.712 49.937 .000

CAS*TT*MT .899 1 .899 5.155 .025

BT*TT*MT 2.003 2 1.002 5.742 .004

CAS*BT*TT*MT 17.877 2 8.939 51.238 0.000

Error 20.934 120 0.174

Total 70030.242 144

Corrected Total 496.068 143

C.A.S: Concentration of alkali solution, B.T: bath temperature, T.T:

time of treatment, M.T: mercerizing tension.

Figure 2. Effect of mercerizing tension on dimensional stability of

the samples; ( ) fabric samples mercerized with 5 % tension, and

( ) fabric samples mercerized with 15 % tension.


shown in Figure 2. Details of the statistical analysis have

been shown in Table 5 (section A).

It is observed that, most of the samples show an increase

in Ks value while mercerizing tension decreases. Only in one

group (group 8 in Table 3) mercerized in time of 240 sec and

alkali concentrations of 300 g/lit, inverse effect were

observed. This may be because of structural distortion in the

fibers and respectively the fabric at this condition. Also, this

result shows interactive effect of three mentioned parameters

on dimensional stability of the fabric.

Effect of Concentration of Alkali Solution

In this part of the work paired t test was used to analyze

difference between Ks value of the samples in groups

Table 5. Results of paired T test to compare Ks value for each group (two samples) in Figures 2-4

Paired T test for mercerizing tension (section A)

Pairs (samples)

95 % Confidence interval of the

difference t dfSig.

(2-tailed)Mean Std.Deviation Std. Error Mean Lower Upper

1-2 1.85667 .25890 .10569 1.58497 2.12836 17.567 5 .000

3-4 4.40500 .26037 .10629 4.13176 4.67824 41.442 5 .000

5-6 2.62333 .86945 .35495 1.71090 3.53577 7.391 5 .001

7-8 3.14000 .51602 .21067 2.59847 3.68153 14.905 5 .000

9-10 2.75000 .34106 .13924 2.39208 3.10792 19.751 5 .000

11-12 1.49833 .43815 .17887 1.03852 1.95815 8.376 5 .000

13-14 .21333 .79731 .32550 -.62339 1.05006 .655 5 .541

15-16 -.68000 .87350 .35660 -1.59668 .23668 -1.907 5 .115

17-18 1.48833 .52213 .21316 .94039 2.03627 6.982 5 .001

19-20 .32833 .39927 .16300 -.09068 .74734 2.014 5 .100

21-22 1.16500 .72511 .29603 .40404 1.92596 3.935 5 .011

23-24 3.13500 .29105 .11882 2.82956 3.44044 26.384 5 .000

Pairs (samples) Paired T test for concentration of alkali solution (section B)

1-13 -1.61500 .44311 .18090 -2.08002 -1.14998 -8.928 5 .000

2-14 -3.25833 .78446 .32025 -4.08157 -2.43509 -10.174 5 .000

3-15 -.87167 .93602 .38213 -1.85396 .11063 -2.281 5 .071

4-16 -5.95667 .46890 .19143 -6.44875 -5.46459 -31.117 5 .000

5-17 1.11833 .67360 .27500 .41143 1.82523 4.067 5 .010

6-18 -.01667 .73940 .30186 -.79262 .75928 -.055 5 .958

7-19 1.80500 .29194 .11918 1.49863 2.11137 15.145 5 .000

8-20 -1.00667 .47626 .19443 -1.50647 -.50686 -5.177 5 .004

9-21 1.61667 .51872 .21177 1.07231 2.16103 7.634 5 .001

10-22 .03167 .48979 .19996 -.48234 .54567 .158 5 .880

11-23 1.87833 .62566 .25543 1.22174 2.53493 7.354 5 .001

12-24 3.51500 .71029 .28997 2.76960 4.26040 12.122 5 .000

Pairs (samples) Paired T test for time of treatment (section C)

1-3 -1.45333 .30657 .12516 -1.77506 -1.13161 -11.612 5 .000

2-4 1.09500 .23054 .09412 .85306 1.33694 11.634 5 .000

5-7 -.72167 .49665 .20275 -1.24286 -.20047 -3.559 5 .016

6-8 -.20500 .68669 .28034 -.92564 .51564 -.731 5 .497

9-11 .17167 .77657 .31703 -.64329 .98662 .541 5 .611

10-12 -1.08000 .67445 .27534 -1.78779 -.37221 -3.922 5 .011

13-15 -.71000 .99886 .40778 -1.75824 .33824 -1.741 5 .142

14-16 -1.60333 .59976 .24485 -2.23274 -.97393 -6.548 5 .001

17-19 -.03500 .60781 .24814 -.67285 .60285 -.141 5 .893

18-20 -.03500 .60781 .24814 -.67285 .60285 -.141 5 .893

21-23 .43333 .59976 .24485 -.19607 1.06274 1.770 5 .137

22-24 2.40333 .42184 .17221 1.96064 2.84602 13.955 5 .000


illustrated in Figure 3. Results of the analysis are shown in

Table 5 (section B). It was concluded that, dimensional

stability of most of the samples increased by increase in

concentration of alkali solution in mercerization bath when

temperature of the bath was low. This improvement is

attributed to the decline in alkali hydration and better

penetration of NaoH into the fibers. Increasing the

concentration of soda in mercerization bath, usually leads to

better dimensional stability, because of less hydrolysis of

alkali and better penetration in oriented and crystalline parts

of the fiber. However, rising temperature and concentration

of alkali solution together will decrease the trend of

dimensional stability improvements probably due to

meaningful interaction between these two parameters and

dimensional stability of the fabric (Table 4).

It seems that, rising temperature and amount of alkali

agent loosens the fiber structure, hydrates more alkaline and

distorts the molecular chain orientations and then the final

result is a decline in dimensional stability factor (Ks). This

trend can be seen in Figure 3 for groups 9, 11, 12. For fabrics

in these groups mercerization was carried out at temperature

of 60 oC and time of 240 sec. Two mentioned parameters

accompanied by concentration of alkali solution had interactive

effect on dimensional stability. It can be observed in Figure 3

that in temperature of 60 oC and time of 240 sec, less value

of alkali concentration (200 g/lit) was required to increase

dimensional stability of the fabric.

Effect of Time of Treatment

Mercerization process will be completed by increasing

time of treatment. However, required time to achieve

complete mercerization purposes is different for a sample

according to the concentration of alkali solution, bath

temperature and also fabric type [15,16].

In this study increasing time of treatment usually leads to

obtain higher amounts of Ks which results in more

dimensional stability improvement. However in some groups,

increasing time caused a decline in Ks probably due to

interactive effect of bath temperature, alkali concentration

and time of treatment on dimensional stability of the fabric

(Table 4).

As shown in Figure 4 in some samples adding time results

in better dimensional stability. But comparing dimensional

stability factor (Ks) between groups 3, 11, 12 shows that,

increasing time of treatment in high concentration of alkali

agent and high temperature conditions leads to structural

distortion and less dimensional stability. These samples were

mercerized in temperature of 40-60 oC and alkali concentration

of 300 g/lit.

Effect of Bath Temperature

As mentioned before, by reducing temperature, the viscosity

of solution increases; however the penetration of solution in

the fiber decreases. Raising temperature leads to loosening

the fiber structure and more diffusion of solution, in addition

to the decline in viscosity [13]. Therefore a suitable

Figure 3. Effect of concentration of alkali agent on dimensional

stability of the samples; ( ) fabric samples mercerized in 200 g/lit

concentration of alkali agent and ( ) fabric samples mercerized in

300 g/lit concentration of alkali agent.

Figure 4. Effect of time of treatment on dimensional stability of

the samples; ( ) fabric samples mercerized in 120 sec and ( )

fabric samples mercerized in 240 sec.

Figure 5. Effect of bath temperature on dimensional stability of the

samples; ( ) fabric samples mercerized at 20 degree centigrade

temprature, ( ) fabric samples mercerized at 40 degree centigrade

tempratue, and ( ) fabric samples mercerized at 60 degree

centigrade temprature.


temperature can be obtained in mercerization treatment to

improve fabric properties.

Figure 5 shows the effect of bath temperature on

dimensional stability of the samples. Analysis of variance

(ANOVA test) and Tukey multiple rang test were used to

study statistical meaning of the difference between and

within Ks value for the samples shown in Figure 5 respectively.

The results of the analysis have been represented in Table 6.

It is observed that, in most of the samples raising

temperature from 20 oC to 40 oC adds and improves the

dimensional stability of the fabrics but more increase in

temperature leads to decline in Ks value. Comparing

dimensional stability for group 7 shows that increasing bath

temperature from 20 to 40o

C increases dimensional stability

of the samples and leads to higher Ks values. A temperature

of 40 oC is usually the most proper temperature in which the

highest dimensional stability is obtained.

However, since more value was considered for tension

(15 %) in mercerization process for fabric samples in groups 3,

rising temperature more than 40 oC is mandatory to increase

Ks value and dimensional stability. In these samples more

time of treatment (240 sec) was used to achieve purpose of

the mercerization. It is probably attributed to the improvement

in orientation of molecular chains along fiber axes in higher

tension.

Simultaneous Effect of All the Variables on Dimensional

Stability of the Fabrics

The results of investigation on simultaneous effect of all

the variables on dimensional stability of the fabrics are

shown in Table 2. Value of the area geometry constant (Ks)

which is related to SD or the number of loops per square

Table 6. Analysis of variance (ANOVA test) and results of Tukey,s procedure multiple range test to compare the Ks value in samples with

different bath temperature (Figure 5)

ANOVA test Tukey test: subset for alpha=0.05

Group: 1-5-9 Sum of squares df Mean square f Sig. Sample N 1 2 3

Between groups

Within groups

Total

39.821

4.073

43.894

2

15

17

19.911

0.27273.333 0.000

1

5

9

6

6

6

20.10 24.16

24.37


Between groups

Within groups

Total

39.843

8.259

48.101

2

15

17

19.921

0.5536.182 0.000

2

6

10

6

6

6

18.4521.88

21.62


Between groups

Within groups

Total

34.295

3.293

37.588

2

15

17

17.148

0.22078.110 0.000

3

11

7

6

6

6

21.56 24.14

24.88


Between groups

Within groups

Total

83.149

6.671

89.020

2

15

17

41.574

0.44593.486 0.000

4

8

12

6

6

6

17.15 21.92

22.71


Between groups

Within groups

Total

5.805

3.130

8.934

2

15

17

2.902

0.20913.911 0.000

13

21

17

6

6

6

21.71 22.76

23.04


Between groups

Within groups

Total

0.299

3.570

3.869

2

15

17

0.150

0.2380.629 0.547

22

14

18

6

6

6

21.59

21.50

21.53


Between groups

Within groups

Total

1.793

4.259

6.052

2

15

17

0.897

0.2843.158 0.072

23

15

19

6

6

6

22.32

22.43

23.07


Between groups

Within groups

Total

54.664

3.077

57.740

2

15

17

27.332

0.205133.261 0.000

24

20

16

6

6

6

19.19 22.74

23.11


centimeter is obtained from multiplying Kw by K

c and show

the number of loops per one square centimeter. If the sample

has high shrinkage along length (wale) and width (course)

directions, the number of loops per area in the fabric increases.

Statistical analysis showed that, sample No.7 had the

highest amount of Ks that is 24.88. This sample has the

highest shrinkage along course and wale directions. High

shrinkage is the result of carrying out mercerization process

at the temperature of 40o

C

and in 5 % of tension accompanied

by 240 sec time of treatment. Probably, high temperature

and low tension leads to more loosening in fiber structure of

the sample and therefore more penetration of soda solution

with less viscosity which produces more swelling and

shrinkage. Increase in Ks gives more dimensional stability

and the fabric achieves a more normal condition.

Also, analysis showed that, the mean value of Ks has no

significant difference among samples No.5, 9, 7, and 11. It

means that, the equal dimensional stability or Ks value can be

obtained in easier mercerization condition in comparison

with the status used for sample No.7. Sample No.5 is

mercerized in 200 g/lit of alkali concentration and at 40 oC

with 5 % tension and in 120 sec; it has proper process

conditions (Ks=24.12) compared with sample No.7 but, the

difference in Ks value and dimensional stability between two

samples is not meaningful statistically.

Finally the results confirm that, the mercerization process

improves a various properties in a plain weft knitted fabric in

addition to the improvements it can make in fabric shrinkage

and dimensional stability, close to theoretical analysis.

Compared with other dimensional stability improvement

methods, in which the Ks value was raised to 24.35 [18],

mercerization treatment is highly considerable as a method

for dimensional stabilization of cotton plain weft knitted

fabric. More investigation is in progress concerning a wider

domain of variables in order to increasing the Ks factor and

achieving more accurate results.

Conclusion

In this research, mercerization treatment has been used as

a suitable and effective method to improve dimensional

stability of plain weft knitted fabric. Knitted fabric 26

samples were mercerized by considering variation in time of

treatment, bath temperature, concentration of alkali solution

and mercerization tension. After treatment values of constants

termed fabric dimensional parameters were calculated. Then

obtained values were compared with those of un-treated

ones subjected to dry and wet relaxation.

Study shows that, decrease in mercerization tension led to

increase in dimensional stability of the fabrics. Increasing

the concentration of soda in mercerization bath, usually led

to better dimensional stability, but rising temperature will

decrease the trend of dimensional stability improvements.

Increasing time usually led to achieve higher amounts of Ks.

A temperature of 40 oC is usually the most proper

temperature in which the highest dimensional stability is

obtained. However mentioned trend for the effect of the

variables on dimensional stability was quashed due to

interactive effect of the parameters and dimensional stability.

Also, research showed that, the highest amount of Ks (24.12)

can be obtained in alkali concentration of 200 g/lit, 40 oC

with 5 % tension and in 120 seconds.

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Dimensional stabilization of cotton plain weft knitted fabric using mercerization treatment

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