chapter 9 nano silver finishing of copper core...

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CHAPTER 9

NANO SILVER FINISHING OF COPPER CORE YARN

FABRIC TO IMPROVE THE EMSE

9.1 INTRODUCTION

Nanotechnology protective treatment is the latest trend in textile

finishing and has been proved to be a useful technology in improving the

performance of textiles. In this present work, the electromagnetic shielding

effectiveness of silver nanofinish copper core yarn fabrics were studied and

explained in this chapter. The silver nanoparticles were applied on woven

plain fabric by pad-dry process. Silver nanoparticles were applied on copper

core yarn woven plain fabric using three different variables namely

concentration, application temperature and curing time. Sixteen samples were

taken for application of silver nanoparticles and testing by using Factorial

Design method of analysis. The electromagnetic shielding effectiveness

values for different applying conditions were measured, tabulated and

discussed in this chapter.

9.2 RESULT AND DISCUSSION

9.2.1 Surface morphology of Silver Nano-particles - SEM

Lower levels of magnification (2500 X) of copper core yarn cotton

fabric samples, treated with nano-silver (20 ml/l), showed clear images of

fibres with surface level cracks associated with them, in the middle of the

fibre and, the inherent convolutions of the cotton fibres (Figures 9.1 and 9.2).

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Treatment with the suspensions of nano-silver resulted in the deposition and

firm attachment of silver particles over the surface of the fabrics. However,

such deposits appeared to be concentrated in certain places, which obviously

could result in agglomeration of the particles. Surface deposits of nano-

particles, concentrated in the localized way, over the fabric surface can be

expected to scatter the electromagnetic interference rays rather than resulting

a uniform reflection. The samples treated with higher concentration levels of

silver nano-particles showed higher deposits on to the surface of fibres than

the samples treated with low concentration levels (Figure 9.2). The difference

in concentration levels are expected to have different levels of influence on

the electromagnetic shielding effectiveness against electromagnetic

interference.

Magnification at higher levels (15000 X), for the samples treated

with low and high concentration levels of nano-particles, revealed the surface

deposits of that were mainly aggregated to an extent of ~ 500 nm (Figure 9.3).

Also, the deposits were found to be high near the asperities, surface cracks

and cross-over points between the fibres, which could exercise additional

holding by trapping the nano-particles, compared to the smooth surfaces of

the fibres. The significant amounts of nano-particles that appeared to be

present throughout the fibre surface, are expected to have considerable

influence on the electromagnetic shielding properties of the fabrics. When

such depositions are present in the fabric samples with the yarns made of

conductive core yarns, more attenuation can be expected from those samples.

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Figure 9.1 Samples treated with low concentration of silver nano-

particles - SEM

Figure 9.2 Samples treated with high concentration of silver nano-

particles- SEM

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Figure 9.3 Deposits of Silver Nano-particles at higher magnification

levels (15000 X) - SEM

9.2.2 Antibacterial Effects of Silver Nano Finished Fabric

Nanosized silver particles in colloidal solution had excellent

antibacterial effect on all specimens against gram-positive and gram-negative

bacteria. Table 5.4 shows the antibacterial effect of nanosized silver colloidal

solution on processed fabric. It is found that the bacterial reductions of all

samples were very excellent against E-coli.

In this study, the applications of silver Nanoparticles were

investigated by growing E.coli on agar plates. When Nanoparticles were

present on agar plates, they could completely inhibit the bacterial growth.

However, inhibition depends upon concentration of silver Nanoparticles.

In contrast, silver Nano particles in liquid medium, even at higher

concentration, caused only delayed growth of E.coli. The concentration of

nano particles decreases, allowing resumed growth of bacterial cells.

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It is well known that outer membrane of E.coli cells is

predominantly constructed from tightly packed lipopolysaccharides

molecules, which provide an effective permeability barrier. It is clear that

treated bacteria also showed significant changes in and damages in the

membranes. The fabrics padded through 30 ml/l silver colloidal solution also

had better bacterial activity than the samples treated with 20 ml/l and 10 ml/l

solution at 22°C as shown in the Table 9.1. Results obtained in the

antimicrobial test shows that, silver concentration at 10 ml/l and temperature

at 22°C the antimicrobial activity increases with increase in curing time. The

higher bacterial inhibition also obtained at 30 ml/l and 22°C with the increase

in curing time. The bacterial inhibition at 20°C is very less when compared to

22°C and 24°C with increase in curing time as shown in the Table 9.1.

Table 9.1 Antimicrobial Activity of Nano Silver finished Fabrics

S.No. X1 in ml/l X2 in °C X3 in min Antimicrobial activity Diameter of clearance

in mm 1 20 22 3 7 2 30 22 1.5 14 3 30 24 1.5 3 4 30 20 3 2 5 30 20 4.5 1 6 20 24 1.5 2 7 20 20 4.5 1 8 20 24 4.5 2 9 20 20 1.5 1 10 30 24 4.5 3 11 10 24 3 6 12 10 24 1.5 6 13 10 20 3 2 14 30 24 3 6 15 10 22 4.5 9 16 10 22 1.5 8 17 Untreated Fabric 0

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Hence it is understood that the damages due to bacterial effect of

any sensitive equipment is very much minimized.

9.2.3 Influence of Concentration, Temperature and Curing Time on

S3 Values (EMSE)

The Factorial Design for three variables at three levels, along with

the S3 (EMSE) values (i.e. electromagnetic shielding effectiveness) are given

in Table 9.2.

Table 9.2 Electromagnetic Shielding Effectiveness of Silver Nano

Finished Copper Core Yarn Fabric

X1 X2 X3

Electromagnetic Shielding Effectiveness at different frequencies S3 (EMSE)

200

MH

z

300

MH

z

400

MH

z

500

MH

z

600

MH

z

700

MH

z

800

MH

z

900

MH

z

1000

M

Hz

20 22 3 23 29 27 28 30 34 34 38 39 30 22 1.5 26 28 30 31 34 39 41 44 45 30 24 1.5 28 30 32 32 38 41 43 45 46 30 20 3 29 32 35 39 39 42 44 47 48 30 20 4.5 31 37 40 43 43 45 47 50 52 20 24 1.5 21 22 25 26 29 32 34 37 38 20 20 4.5 25 25 28 29 31 35 35 39 41 20 24 4.5 26 27 29 29 32 37 39 42 43 20 20 1.5 21 21 24 25 26 31 33 36 37 30 24 4.5 35 39 45 48 40 50 52 42 57 10 24 3 19 20 22 23 23 26 31 34 35 10 24 1.5 18 18 21 21 23 25 31 33 34 10 20 3 19 19 21 21 22 25 29 33 34 30 24 3 32 38 42 45 47 48 52 52 55 10 22 4.5 20 20 23 25 25 30 32 35 36 10 22 1.5 17 18 20 20 22 25 39 32 34

Untreated 14 16 19 20 21 23 27 28 31

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Table 9.3 Regression and Correlation Co-efficient For EMSE

Frequency In MHz

Regression equation for EMSE (S3)

Correlation co-efficient

200 -1.6535459+0.5594*x1+0.4435*x2+1.5904*x3 0.99100

300 -6.997644+0.72771*x1+0.5745*x2+1.94181*x3 0.97664

400 -9.97445+0.77362*x1+0.733386*x2+2.2264*x3 0.97299

500 -8.85820+0.8565*x1+0.6276*x2+2.59429*x3 0.96363

600 -2.504692+0.8441*x1+0.55779*x2+1.4399*x3 0.97776

700 -4.70532+0.87466*x1+0.727708*x3+1.9958*x3 0.99318

800 0.824345+0.70327*x1+0.89503*x2+1.12046*x3 0.97770

900 20.596712+0.6552*x1+0.1462*x2+0.1462*x3 0.97840

1000 3.27035+0.7768*x1+0.77328*x2+1.9364*x3 0.98706

The influence of concentration, temperature and curing time on S3

(EMSE) values at various frequencies ranges of 200, 300, 400, 500, 600, 700,

800, 900 and 1000 MHz are shown in the Figure 9.4a to 9.12c. It was found

that the concentration and curing time had significantly influenced the electro

magnetic shielding effectiveness.

The influence of concentration and temperature on S3 (EMSE)

values for a curing time at 4.5 min was studied. The S3 (EMSE) values

increase with increase in concentration of silver nanoparticles. This can be

attributed to the fact that the number of Nano Silver particles in the fabric

increases, so that a greater amount of absorption and reflection of electro

magnetic waves occur, which leads to more electro magnetic shielding

effectiveness. The combined effects of concentration and temperature on S3

(EMSE) values indicate that the lowest concentration and temperature gives

lower S3 (EMSE) values, which indicates the reducing electro magnetic

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shielding effectiveness. The influence of concentration and curing time on S3

(EMSE) values for a temperature at 24°C. With the increase in curing time,

the S3 (EMSE) values increase. This is because of the higher curing time, the

silver nanoparticles compactly bound with the surface of the yarn and fabric,

which leads to have better electromagnetic shielding effectiveness. The

influence of temperature and curing time on S3 (EMSE) values at 30ml/l was

studied. The S3 (EMSE) values did not increase with increase in temperature,

compared to increase in concentration and temperature. The influence of

concentration and curing time on the S3 (EMSE) values for a temperature

240C was shown in the Figure 9.4c, 9.5c, 9.6c, 9.7c, 9.8c, 9.9c, 9.10c, 9.11c

and 9.12c. From the above contours, the best results were found between 0.5

to 1.0 level of concentrations (30ml/l), followed by 0 level (concentrations

22 ml/l) and the worst results for -0.5 to -1.0 level (concentrations 20 ml/l).

The influence of the curing time on the S3 (EMSE) values for a

temperature 20oC and concentration 30ml/l, were shown in the Figure 9.4a,

9.4c, 9.5a, 9.5c, 9.6a, 9.6c, 9.6a, 9.6c, 9.7a, 9.7c, 9.8a, 9.8c, 9.9a, 9.9c, 9.10a,

9.10c, 9.11a and 9.11c. From the contours the best results were found

between 0.5 to 0.1 level of curing times (4.5 minutes), followed by 0 levels

(curing time 3 minutes) and the worst results for -0.5 to -1.0 level (curing time

1.5 minutes). It can be observed from the Table 9.2, that the Nano silver

finished fabrics have better electromagnetic shielding effectiveness than the

untreated fabrics of copper core yarn fabrics. It was also found that the

electromagnetic shielding effectiveness of silver nano finished fabrics was

improved by approximately 20 to 55 % that of the untreated copper core yarn

fabric, which depends upon the concentration and curing times. The

maximum electro magnetic shielding effectiveness of silver Nano finished

fabric (concentration 30ml/l, curing time 4.5 minutes and temperature 24oC)

was obtained in the range of 48 to 57 dB in a frequency range of 500 to 1000

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MHz. It is also found that with an increase in frequency, the electro magnetic

shielding effectiveness increases as shown in Table 9.2.

The regression equations were framed using the co-efficient obtained

in the Factorial Design experimental designs to assess the electromagnetic

shielding effectiveness of various frequency level (Table 9.3).Various

equations framed in this exercise , appeared to ‘fit’ in a better way with the

actual values obtained at those frequencies, expressed by the higher

correlations values . However, at higher frequency levels, 900 and 1000 MHz,

some other factors also might have contributed to the ‘calculated value’, since

the constant values obtained in these equations were high.

Concentration (ml/l)

Figure 9.4(a) Effect of concentration and Temperature on EMSE

(200MHz)

Tem

pera

ture

(°C

)

226

Tim

e (m

in)

Temperature (°C)

Figure 9.4 (b) Effect of Temperature and Time on EMSE (200MHz)

Tim

e (m

in)

Concentration(ml/l)

Figure 9.4 (c) Effect of Concentration and Time on EMSE (200 MHz)

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Tem

pera

ture

(°C

)



(300MHz)

Temperature (°C)

Figure 9.5(b) Effect of Temperature and Time on EMSE (300MHz)

Tim

e (m

in)

228

Tim

e (m

in)


Figure 9.5 (c) Effect of Concentration and Time on EMSE (300MHz)

Tem

pera

ture

(°C

)



(400MHz)

229

Tim

e (m

in)

Temperature (°C)


Tim

e (m

in)


Figure 9.6(c) Effect of Concentration and Time on EMSE (400MHz)

230

Tem

pera

ture

(°C

) C

C


Figure 9.7(a) Effect of concentration and Temperature on EMSE (500MHz)

Temperature (°C)


Tim

e (m

in)

231

Tim

e (m

in)


Figure 9.7(c) Effect of Concentration and Time on EMSE (500 MHz)

Tem

pera

ture

(°C

)



(600MHz)

232

Tim

e (m

in)

Temperature (°C)


Tim

e (m

in)


Figure 9.8(c) Effect of Concentration and Time on EMSE (600MHz)

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(700MHz)

Temperature (°C)


Tim

e (m

in)

Tem

pera

ture

( °C

)

234


Figure 9.9 (c) Effect of Concentration and Time on EMSE (700 MHz)



(800MHz)

Tim

e (m

in)

Tem

pera

ture

(°C

)

235

Temperature (°C)




Tim

e (m

in)

Tim

e (m

in)

236



(900MHz)

Temperature (°C)


Tem

pera

ture

(°C

) Ti

me

(min

)

237





(1000MHz)

Tim

e (m

in)

Tem

pera

ture

(ºC

)

238

Temperature (°C)




Tim

e (m

in)

Tim

e (m

in)

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The three optimum process parameters obtained from the graphs

are analyzed for highest occurrence of each process parameter and one set of

process parameters are obtained i) To find out the optimum level of each

variable, ii) To find out best trial. The process parameters for optimum results

of antimicrobial and Electromagnetic shielding effectiveness are shown in the

Table 9.4.

Table 9.4 optimum process parameters

For antimicrobial activity For EMSE values

Optimum levels

Concentration : +1 Concentration: +1

Temperature : 0 Temperature : 0

Curing Time: +1 Curing Time: +1

Over All Concentration: +1, Temperature: 0, Curing Time: +1

9.3 CONCLUSIONS

The Nano silver finished fabrics were produced using Copper/Cotton

core spun yarns and Factorial Design has been used in this present work to

analyse the effects of different combinations of process parameters. 16 trials

were derived from Factorial Design rather than 27 trials and is an added

advantage. The detailed regression analysis shows that the concentration,

temperature and curing time are highly significant in electromagnetic

shielding effectiveness of silver nano finished fabric. The electromagnetic

shielding effectiveness of silver nano finished fabrics were improved by

approximately 20 to 55% that of the untreated copper core yarn fabrics. The

process parameters for optimum results of antimicrobial and electromagnetic

shielding effectiveness were also identified.

chapter 9 nano silver finishing of copper core...

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