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CHAPTER 3

MATERIALS AND METHODS

3.1 INTRODUCTION

This chapter deals with the materials and experimental methods

used in the present research to impart antimicrobial finish to the fabrics. The

material details include fabric particulars, precursors, stabilizing agents for

nano particles preparation and other auxiliaries used for antimicrobial finish.

The methods used are briefly explained in this chapter such as preparation of

nano particles, finishing procedures, characterization and testing methods for

antimicrobial efficiency and fabric properties.

3.2 MATERIALS

The materials used in the present study i.e., the fabrics chosen for

finishing and chemicals and materials used for nano particles preparation and

testing the antimicrobial activity are presented in the following session.

The following figure (Figure 3.1) shows the overall research

methodology adopted in the current research work.

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Purchase of Woven and

Knitted Cotton fabrics

Analysis of the Characteristics of the

Cotton fabrics

1. Breaking Strength

2. Fabric construction

3. Bursting strength

4. Pilling

5. Dimensional stability

Woven Fabrics Knitted Fabrics

Plain

Weave

Honeycomb

Weave

Twill

Weave

Single

Jersey

Double

Jersey

Pique

Synthesis of zinc oxide and copper oxide

nano particles by Wet Chemical method

Characterization of the

nano particles

Application of nano particles on

fabric by Pad – Dry – Cure method

Figure 3.1 (Continued)

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Physical and Functional

Characterization of the finished fabrics

Antibacterial Testing

1. Agar diffusion test –

ATCC 147 (Qualitative

method)

2. Shake flask test –

AATCC 100

(Quantitative method)

Physical Characterization

1. Fourier Transform Infra

Red Spectroscopic analysis

2. Scanning Electron

Microscopic analysis

3. X – Ray Diffraction

Spectroscopic analysis

Microencapsulation of nano particles by ionic gelation method

Nanoencapsulation of nano particles

Product Development

1. Surgical Gloves

2. Cap

3. Napkins

Field Trials for the Developed Products

Synthesis of nano particles composites

Wash Durability Testing

Wash Durability Testing

Wash Durability Testing

Figure 3.1 Overall Research Methodology adopted in the current study

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3.2.1 Fabrics Used in the Present Research Work

Hundred percent bleached, mercerized, cotton woven and knitted

fabrics have been used in this study for antimicrobial finish. Woven fabrics

used for various experiments were plain, honeycomb and twill weave and the

knitted fabrics used were single jersey, double jersey and pique fabric. These

fabrics were procured from textile industry, Tirupur.

3.2.2 Chemicals Used in Different Experiments

Chemicals have been obtained from Himedia, Lobachime, Nice and

Rankem Laboratories, Mumbai, India and Jiangsu Huaxi International

Laboratories, China and these were of the highest purity available. In order to

provide antimicrobial finish, sodium hydroxide, copper sulphate and zinc

nitrate were used as precursors and soluble starch was used as stabilizing

agent. The chemicals used for each process are given in Table 3.1.

Table 3.1Chemicals used for different experiments

S.No. Chemicals used Make Experiment

1. Soluble starch HimediaStabilizing agent – Nano particle

preparation

2.Zinc nitrate / Copper

sulphate

Nzsice /

HimediaPrecursors – Nano particle

preparation3. Sodium hydroxide Nice

4. Sodium lauryl sulphate Rankem

Non – ionic detergent –

Finishing of nano particles on

fabrics

5. Sodium alginate LobachimeMicroencapsulation of nano

particles6. Calcium chloride Rankem

7.Bovine albumin

fractionHimedia

Wall material –

Nanoencapsulation of nano

particles

8. EthanolJiangsu Huaxi

International

Nanoencapsulation of nano

particles

9. Glutaraldehyde NiceHardening agent –

Nanoencapsulation

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3.3 PREPARATION OF ZINC OXIDE AND COPPER OXIDE

NANO PARTICLES

In the present research work, nano particle preparation using zinc

nitrate and copper sulphate was attempted. The prepared nano particles were

microencapsulated using calcium alginate as the wall material. Similarly,

protein solution was used as the wall material, hydrochloric acid for adjusting

the pH and glutaraldehyde was used as hardening agent for the preparation of

nanocapsules.

3.3.1 Preliminary Antibacterial Screening

In order to impart antibacterial activity to the selected fabrics,

various chemicals were coated to the fabric. The antibacterial activity of

various agents such as zinc oxide, commercial antibacterial agent and citric

acid was tested. The antibacterial activities of the above agents were

compared with the nano particles prepared using various precursors and

stabilizing agents like zinc nitrate and / or copper sulphate (5 – 25%), sodium

hydroxide and soluble starch.

3.3.2 Synthesis of zinc oxide nano particles (Yadav et al 2006)

Nano particles were prepared using wet chemical method using

precursors and stabilizing agents. A typical procedure for making nano-zinc

oxide particles was followed as discussed by Yadav et al (2006). The zinc

oxide nano particles were prepared by wet chemical method using zinc nitrate

and sodium hydroxide as precursors and soluble starch as stabilizing agent.

0.1% starch solution was prepared using a microwave oven. 0.1 mol of zinc

nitrate was added to the above starch solution. The resulting solution was then

kept under constant stirring using a magnetic stirrer to completely dissolve the

zinc nitrate. After complete dissolution of zinc nitrate, 0.2 M sodium

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hydroxide solution was added carefully drop-wise along the sidewalls of the

solution vessel with the solution under continuously stirring. The reaction was

allowed to proceed for 2 hr after complete addition of sodium hydroxide.

After completion of reaction, the solution was allowed to settle overnight. The

supernatant liquid was then carefully decanted and the remaining solution was

centrifuged at 10,000 x g for 10 minutes. The nano particles that resulted were

then washed three times using distilled water. Washing was carried out to

remove the by-products and any starch bound to the nano particles. The

washed nano particles were dried overnight at 80 C. Drying helps in the

complete conversion of Zn (OH) 2 to ZnO.

Zn (OH) 2 ZnO + H2O

Zinc hydroxide Zinc oxide + Water

3.3.3 Synthesis of copper oxide nano particles

The procedure adopted for copper oxide nano particles preparation

makes use of copper sulphate and sodium hydroxide as precursors and soluble

starch as stabilizing agent by wet type chemical method. 0.1% starch solution

was prepared using a microwave oven. 0.1 mol of copper sulphate was added

to the above solution. The resulting solution was then kept under constant

stirring using a magnetic stirrer to completely dissolve the copper sulphate.

After complete dissolution of copper sulphate, 0.2 M sodium hydroxide

solution was added carefully drop-wise along the sidewalls of the solution

vessel with the solution under continuously stirring. The reaction was allowed

to proceed for 2 hr after complete addition of sodium hydroxide. After

completion of reaction, the solution was allowed to settle overnight. The

supernatant liquid was then carefully decanted and the remaining solution was

centrifuged at 10,000 X g for 10 minutes. The nano particles that resulted

were then washed three times using distilled water. Washing was carried out

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to remove the by-products and any starch bound to the nano particles. The

washed nano particles were dried overnight at 80 C. Drying

3.4 CHARACTERIZATION OF ZINC OXIDE AND COPPER

OXIDE NANO PARTICLES

In order to determine the size of the nano particles, the synthesized

nano particles were characterized. The zinc oxide and copper oxide nano

particles prepared by the above method were characterized using Jeol Model -

6390 Scanning Electron Microscopy (SEM). The image mode of the

microscopy is secondary electron image, detected by the E. T detector. The

electron gun used in the microscopic analysis accelerated at voltage range of

0.5 – 30 KV and the filament is pre-centered tungsten hairpin filament. The

surface topography of zinc oxide nano particles finished fabric was observed

with a scanning electron microscope (SEM). The physical properties of the

finished fabric were determined and the values compared with those of the

unfinished fabric, which served as the control fabric.

3.5 FINISHING OF COTTON FABRICS WITH ZINC OXIDE /

COPPER OXIDE NANO PARTICLES

The chemically synthesized nano particles were tested by finishing

the cotton fabric with nano particles and then analyzing the antibacterial

activity of the finished fabric by standard methods. Initially a trial procedure

was formulated and and based on it rate of success, coating on the bulk

fabrics were to be done.

A fine-medium weight 100% cotton fabric was used for the purpose

on trial basis. Zinc oxide / copper oxide nano particles were applied to the

fabric by the pad-dry-cure method. The cotton fabric, cut to a size of 30 x 30

cm, was immersed in a solution of 2% zinc oxide nano particles for 5 min and

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then passed through a padding mangle run at a speed of 15 m/min and a

mangle pressure of 15 kgf/cm2. The padded fabric was air-dried and then

cured for 3 min at 140 C in hot air oven. The finished fabric was then

immersed for 5 min in 2 g/l of sodium lauryl sulphate to remove any unbound

nano particles. The fabric was next rinsed 10 times to completely remove any

traces of soap. The fabric was finally dried in ambient air. The antibacterial

activity of the finished fabric was tested qualitaitively and quantitatively. The

same procedure of coating with copper and zinc nano particles and the same

method of antibacterial testing were carried out for the selected bulk fabrics as

the trial method produced valuable results.

3.6 PHYSICAL TESTING OF FABRIC

Since finished product performance relates to the testing of fabric

samples, the textile industry acknowledges the importance of testing to

achieve high quality products. The physical characteristics of both the

untreated and treated fabrics were tested according to the standard methods

mentioned below.

3.6.1 Fabric Construction

In the woven fabric thread count is a measure of the coarseness or

fineness of fabric. The number of weft threads per inch of woven fabric is

referred as picks per inch (or p.p.i.). In general, the higher the picks per inch,

the finer the fabric is. Ends per inch (or e.p.i.) are the number of warp threads

per inch of woven fabric. In general, the higher the ends per inch, the finer the

fabric is. The thread count is the number of threads counted along two sides

(up and across) of the square inch, added together It is measured by counting

the number of threads contained in one square inch of fabric or one square

centimeter, including both the length (warp) and width (weft) threads.

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For the knitted fabrics courses and Wales per cm or inch are

measured by placing an inch or centimeter glass on the fabric, and counting

the number of courses and Wales, which are contained within the area of the

knitted fabric. The mean values of courses/inch and Wales/inch was then

calculated and the product of this mean value was used to determine the stitch

density of the sample, which is usually considered to indicate shrinkage. The

number of course turns present in crosswise direction of knitted fabric in one

inch was determined as course per inch. The number of Wales present in

length wise direction of knitted fabric in one inch was determined as Wales

per inch.

3.6.2 Bursting Strength

This test method describes the measurement of the resistance of

textile fabrics to bursting using the hydraulic diaphragm bursting tester. This

test method is generally applicable to a wide variety of textile products. The

burst strength of a fabric is the amount of force required to rupture a fabric by

distending it with a force (ASTMD 3786-87). The standard test method for

Hydraulic Bursting strength of knitted goods –Diaphragm Bursting strength

test method, ASTM D 3786-87 was performed. This test method utilizes a

pneumatic loading mullen burst tester. The fabrics were conditioned to

standard testing conditions. Five random sites on each fabric were tested on

the Mullen Burst Tester. The burst strength for each test site was recorded in

pounds per square inch and an average value was obtained for each type of

fabric.

3.6.3 Abrasion Resistance

The abrasion resistance property was tested with the help of

Martindale abrasion tester. This apparatus gives a controlled amount of

abrasion between fabric surfaces at comparatively low pressures in

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continuously changing direction. Circular specimens of fabric are abraded

under known pressures under a motion which is the resultant of two simple

harmonic motions at right angle to each other. The resistance to abrasion is

estimated by visual appearance or by finding the loss in mass of the

specimens. The fabric sample was prepared and the initial weight was

measured. Then the fabric was abraded for 50 cycles. After these cycles, the

fabric sample was weighed again. The difference in the two weights (initial

and final) was calculated and the percentage weight loss was calculated.

3.6.4 Pilling

Pilling is the formation of clusters of balls of entangled fibers that

appear on the surface of the material as a result of surface abrasion. Pills are

attached to the surface of the fabric giving them an unsightly appearance. ICI

pillbox tester was used to find out the pill formation on the fabrics. For all the

samples, 3000 revolutions were given and the fabrics were assessed for their

grades. Then the fabrics were compared with the pilling standard photographs

for measuring pilling grades.

3.6.5 Dimensional Stability

The dimensional stability of the knitted fabric samples were derived

from lengthwise shrinkage and widthwise shrinkage after laundering. Arial

shrinkage was determined by measuring the sample before and after washing

and the arial shrinkage was calculated by the following equation.

Sa = Slw + Sww – (Slw X Sww) / 100

where Sa - Arial shrinkage

Slw - Lengthwise linear shrinkage (%)

Sww - Widthwise linear shrinkage (%)

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3.7 CHARACTERIZATION OF NANO PARTICLES FINISHED

FABRIC

The characteristics of the nano particles finished fabrics were

tested. The FTIR analysis SEM analysis and X-ray Diffraction Spectroscopic

analysis were performed for studying the nano particle finished fabrics.

3.7.1 FTIR Analysis

FTIR can be used to identify chemicals from spills, paints,

polymers, coatings, drugs, and contaminants. FTIR is perhaps the most

powerful tool for identifying types of chemical bonds (functional groups).

The samples were analyzed for their chemical bonds using FTIR spectroscopy

and the results were compared for further analysis.

3.7.2 Scanning Electron Microscopic Analysis

The surface topography of zinc oxide nano particles finished fabric

was observed with a scanning electron microscope (SEM). The physical

properties of the finished fabric were determined and the values compared

with those of the unfinished fabric, which served as the control fabric.

3.7.3 X-ray Diffraction Spectroscopic Analysis

The X-ray diffraction spectroscopic analysis is a powerful method

by which X-Rays of a known wavelength are passed through a sample to be

identified in order to identify the crystal structure. The wave nature of the X-

Rays means that they are diffracted by the lattice of the crystal to give a

unique pattern of peaks of 'reflections' at differing angles and of different

intensity, just as light can be diffracted by a grating of suitably spaced lines.

The nano particles were characterized for their structure using X-ray

83

diffraction spectroscopy (make: Shimadzu-model XRD 6000). The type of

X-ray tube is Copper and chromium and detector used is scintillation counter.

3.8 ANTIMICROBIAL ASSESSMENT OF TREATED FABRICS

The zinc oxide / copper oxide nano particle finished fabrics were

assessed for their antibacterial efficiency using both the qualitative and

quantitative methods and the results were compared with the untreated cotton

fabrics.

3.8.1 Antibacterial Tests (Qualitative Test–Screening or Presumptive

Test – AATCC 147 1993)

Specimens of the test material including corresponding untreated

controls of the same material were placed in intimate contact with nutrient

agar, which has been previously streaked with an inoculums of a test

bacterium. After incubation, a clear area of interrupted growth underneath and

along the sides of the test material indicated antibacterial activity of the

specimen. A standard strain of bacteria was used, which was specific to the

requirements of the materials under test.

Test bacteria: Staphylococcus aureus (ATCC 6538) and

Escherichia coli (ATCC 11230) were used as standard Gram positive and

Gram-negative organisms respectively.

(i) Culture medium

AATCC bacteriostasis broth / agar medium were used as a growth

medium for evaluation.

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Composition

Peptone : 10 g

Beef extract : 5 g

Sodium chloride : 5 g

Agar : 1.5%

Distilled water : 1000 ml

Heating to boiling was done to dispense ingredients. A pH of

7.0 – 7.2 was adjusted by 1 N sodium hydroxide solution. A quantity of

10.0 0.5 ml of the bacteriostasis broth was dispensed in conventional

bacteriological culture tubes (125 x 17 mm) and sterilized at 103 K Pa

(15 psi) for 15 minutes.

(ii) Maintenance of culture of test organisms:

Using a 4 mm inoculating loop, the culture was transferred daily in

nutrient / bacteriostasis broth for not more than two weeks. At the conclusion of

two weeks, a fresh transplant was made from stock culture. The culture was

incubated at 37 2 ºC (99 3 ºF). The stock cultures maintained on nutrient agar

slants was stored at 5 1 ºC (41 2 ºF) and was transferred once a month to

fresh agar. The purity of the culture was checked by making streak plates

periodically and observed for single species – characteristic type of colonies.

(iii) Test specimens

Test specimens (Antimicrobial treated) and the untreated fabric

samples (control) were taken and were cut into pieces according to convenient

size (20 mm radius) with round shape.

Sterilized nutrient / bacteriostasis agar medium previously sterilized

and cooled to 47 ± 2 ºC (117 ± 4 ºF) was dispensed by pouring 15 ± 2 ml into

each of standard (15 x 100 ml) flat-bottomed Petri dishes. The agar was

85

allowed to solidified and inoculated with a day culture (slant cultures) of the

test organisms. These were placed on to Petri dishes and allowed to harden.

The textile test specimen was placed on the solid agar and attached to it. For

conditioning, the test dish was stored for 24 hours at 5 ºC and then placed in

an incubator. If the fabric curled preventing intimate contact with the

inoculated surface, small sterile glass plates were placed on the ends of the

fabric to hold it in place. The plates were then incubated at 37 ºC for 18-24

hours.

(iv) Evaluation

At the end of the incubation time, the test dishes were observed.

The agar under the sample was also evaluated. This was important if no zones

of inhibition existed. This assessment was made by visual examination as well

as under a microscope with 40 x magnification. The evaluation was made on

the basis of absence or presence of an effect of bacteria in the contact zone,

under the specimen and the possible formation of a zone of inhibition around

the test specimen and the zone of bacteriostasis were measured in mm.

3.8.2 Antibacterial test (Quantitative test- Reference or

Confirmatory test)

Shake flask test (AATCC 100 1993 and JIS L 1902)

Swatches of test and control textile materials already qualitatively

tested for antibacterial activity were evaluated quantitatively. Test and control

swatches were inoculated with the test organisms. After incubation the

bacteria were eluted from the swatches by shaking in known amounts of

neutralizing solution. The number of bacteria present in this liquid was

determined and the percentage reduction by the treated specimen was

calculated.

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(i) Test organisms

Both S. aureus (ATCC 6538) and E. coli (ATCC 11230) were used

for commercial textile samples and only S. aureus was used for all other

treated fabrics.

(ii) Culture medium

AATCC bacteriostasis broth / agar medium were used as a growth

medium for evaluation.

(iii) Maintenance of the culture of test organism

Using a 4 mm inoculating loop, the culture was transferred daily in

nutrient / bacteriostasis broth for not more than two weeks. At the conclusion of

two weeks, a fresh transplant was made from stock culture. The culture was

incubated at 37 2 ºC (99 3 ºF). The stock cultures maintained on nutrient agar

slants was stored at 5 1 ºC (41 2 ºF) and was transferred once a month to fresh

agar. The purity of the culture was checked by making streak plates periodically

and observed for single species – characteristic type of colonies.

(iv) Test specimens

Circular swatches of 4.8 ± 0.1 cm in diameter were cut from the test

fabric. The swatches were stacked in a 250 ml wide mouth glass jar with

screw cap. Swatch of the same fiber type and fabric construction as test

sample containing no antimicrobial finish was used as the control.

(v) Size of the inoculums per sample

About 1.0 ± 0.1 ml of an appropriate dilution of 24-hour culture of

the test organism in nutrient broth was applied. The recovery from the

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untreated control fabric swatches and treated test fabric swatches at 0 contact

time (placed as soon as possible after inoculation) showing a count of

appropriate number of organisms were recorded.

A 24-hour culture of the test organism was shaken and allowed to

stand for 15 - 20 minutes before preparing the inoculums. The swatches were

placed in a sterile Petri dish. Using a micropipette, inoculation was done

making sure that there was even distribution of the inoculums. The swatches

were then transferred aseptically to the jar. The jar tops were closed tightly to

prevent evaporation. Immediately after inoculation about 100 ml of

neutralizing solution (sterile distilled water) was added to each of the jars

containing the inoculated untreated control swatches, the inoculated treated

test swatches and the uninoculated treated swatches. The jars were shaken

vigorously for one minute. The serial dilutions were made with water and

plated (in duplicate) on nutrient agar. Additional jars containing inoculated

untreated control swatches and jars containing inoculated treated test

swatches were incubated at 37 ± 2 ºC (99 ± 3 ºF) for 18 - 24 hours. Similar

jars were incubated for 1 - 6 hours to provide information about the

bactericidal activity of the treatment over such periods. After incubation,

about 100 ml of neutralizing solution was added to jars containing untreated

control swatches and jars containing treated test swatches. The jars were

vigorously shaken for 1 minute. Serial dilutions were made and plated (in

duplicate) on nutrient agar. All the plates were incubated for 48 hours at 37 ±

2 ºC (99 ± 3 ºF).

(vi) Evaluation

The bacterial counts were reported as the number of bacteria per

sample (swatches in jar) not as the number of bacteria per ml of neutralizing

solution. The percentage reduction of bacteria by the treated specimens were

calculated using the following formula,

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100 (B-A) / B = R

Where, R - % reduction

A - the number of bacteria recovered from the inoculated treated

test specimen swatches in the jar incubated over the desired

contact period.

B - the number of bacteria recovered from the inoculated treated

test specimen swatches in the jar immediately after inoculation

(at ‘0’ contact time).

The bacteriostatic and bactericidal effects were calculated by using the

following formula

Growth control F = Mb - Ma

General activity (Bacteristatic activity) L = Ma - Mc

Specific activity (Bactericidal activity) S = Mb - Mc

where Ma - initial concentration of cells (both treated and untreated

control)

Mb - final concentration of cells in control sample after 18 hours

Mc - final concentration of cells in test sample after 18 hours

The percentage reduction of bacteria by the treated specimen

against each test organism was reported.

3.9 STANDARDIZATION OF FINISHING CONDITIONS

In order to standardize the finishing conditions in the pad-dry-cure

method, the padding mangle was run at different pressure conditions and at

different rpm. The nano particles were finished on the fabric at various

89

conditions by maintaining constant pressure and varying the rpm and by

maintaining constant rpm and varying the pressure. The various finishing

conditions employed were 15-kgf/cm2

pressure (15 m/min and 20 m/min

rpm), 20-kgf/cm2

pressure (15 m/min and 20 m/min rpm) and 25-kgf/cm2

pressure (15 m/min and 20 m/min rpm). The finished fabrics were tested for

their antibacterial activity and the best finishing condition was standardized.

3.9.1 Optimization of nano particle Concentration

The prepared nano particles were finished on the fabric at various

concentrations (0.5 - 3.5 %) on the cotton fabric and the antibacterial activity

of the finished fabrics were determined in order to standardize the optimum

concentration to be used.

3.10 WASH DURABILITY TESTING

The nano particles finished cotton fabric was analyzed for their

wash durability by subjecting the sample to washing and testing its

antibacterial efficiency. The cotton fabric finished with the nano particles by

pad - dry - cure method was subjected to washing by industrial machines and

the antibacterial activity of the washed fabric was assessed by AATCC 147

test method.

3.11 MICROENCAPSULATION OF NANO PARTICLES

(Chowdary and Srinivasa 2003)

Microencapsulation is a process in which tiny particles or droplets

are surrounded by a coating to give small capsules many useful properties. A

microcapsule is a small sphere with a uniform wall around it. The material

inside the microcapsule is referred to as the core, internal phase, or fill,

whereas the wall is sometimes called a shell, coating, or membrane. The

90

process of microencapsulation was adopted to provide long term antibacterial

durability to the fabrics finished with nano particles.

3.11.1 Selection of Core and Wall Materials

The nano particles were used as the core material and sodium

alginate was used as the wall material and microencapsulation was carried out

by ionic gelation method.

3.11.2 Microencapsulation by Ionic Gelation Process

Microcapsules containing nano particles were prepared employing

sodium alginate. 3% sodium alginate was prepared and added 2% nano

particles. This was sprayed into calcium chloride solution by means of a

sprayer (Figure 3.2). A spray gun attached to an air compressor was used as

sprayer for this purpose. The droplets were retained in calcium chloride for 15

minutes. The microcapsules were obtained by decantation and repeated

washing with iso propyl alcohol followed by drying at 45 °C for 12 hours.

The microcapsules were then used for finishing on the selected fabrics.

3.11.3 Microscopic Examination of Microcapsule

Microcapsules prepared by ionic gelation method were examined

under the 400X objective of light microscope to study the structure and

stability of the microcapsules.

3.11.4 Fabric Treatment by Exhaustion Method

The fabric sample was finished with the prepared microcapsules

according to the following recipe. The fabric was immersed for 30 minutes.

After 30 minutes, the fabric was removed, squeezed and dried at 80 – 85 ºC in

the oven for 5 minutes and cured at 150 ºC for 2 minutes. Figure 3.2 shows

the sprayer used for microcapsule preparation.

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Recipe

2% Nano particles solution: 10 ml

Temperature of bath : 50 ºC

M: L ratio : 1:20

Citric acid : 8.0%

Time :30

minutes

3.12 NANOENCAPSULATION OF NANO PARTICLES (Weber

et al 2000)

The encapsulation or absorption in capsules of active lipophilic

ingredient is widely used in the fields of cosmetology and dermatology.

Nanocapsules are typically vesicular systems in which an active ingredient is

confined to an aqueous or oily cavity surrounded by a single polymeric

membrane. Nanoencapsulation facilitates better-controlled release and

targeted delivery functions than other techniques. This is an emerging market

and holds a great future potential.

Figure 3.2 Sprayer used for

microcapsule preparation

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3.12.1 Selection of Wall and Core Material

The nano particles prepared were encapsulated using bovine

albumin fraction as the wall material and the nano particles as the core

material.

3.12.2 Procedure

The nano particle enclosed bovine serum albumin protein nano

particles were prepared by coacervation process followed by cross-linking

with glutaraldehyde. The sprayer used during microencapsulation technique

was not used for the nanoencapulation process. The nano particles were

incubated with the required protein solution (2% W/V) for an hour at room

temperature. The pH of the solution was adjusted to 5 .5 by 1M HCL using

digital pH meter. Then ethanol was added to the solution in the ratio of 2:1

(V/V). The rate of ethanol addition was carefully controlled at 1 ml per

minute. The coacervate so formed was hardened with 25% glutaraldehyde for

2 hours to allow cross-linking of protein. Organic solvents were then removed

under reduced pressure by rotary vacuum evaporator and the resulting

nanocapsules were purified by centrifugation at (10,000 rpm) at 4 ºC. Pellets

of nanocapsules thus obtained were then suspended in phosphate buffer (pH -

7.4; 0.1 M) and each sample finally was lyophilized with mannitol (2% W/V).

The prepared microcapsules and nanocapsules were finished onto the fabrics

and the antimicrobial activity was tested as mentioned in section 3.8.1.

3.13 COMPARISON BETWEEN THE MICROENCAPSULATED

AND NANOENCAPSULATED FINISH

The microcapsules and nanocapsules of the zinc oxide / copper

oxide nano particles were finished on the fabrics by pad-dry-cure method. The

finished fabrics were then used for analysis. A comparative study was made

on the antimicrobial activity between the microencapsulated and

nanoencapsulated fabrics.

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3.14 ZINC AND COPPER OXIDE COMPOSITE NANO

PARTICLE PREPARATION

The zinc oxide nano particles and copper oxide nano particles were

combined together to increase the antibacterial activity by preparing

nanocomposites. Zinc and copper oxide nano particles were prepared as

mentioned in section 3.3.2 and the two nano particles were combined in

various propositions (1:1, 1:2, 2:1) and the finished fabrics were tested for

their antibacterial activity according to the test methods given in section 3.8.

3.14.1 Synthesis of Nanocomposites

Nano particles were prepared using wet chemical method using

precursors and stabilizing agents. A typical procedure for making nano-zinc

oxide and nano-copper oxide particles are as follows. The zinc oxide nano

particles were prepared by wet chemical method as discussed by Yadav et al

(2006) using zinc nitrate and sodium hydroxide as precursors and soluble

starch as stabilizing agent. 0.1% starch solution was prepared using a

microwave oven. 0.1 mol of zinc nitrate was added to the above solution. The

resulting solution was then kept under constant stirring using a magnetic

stirrer to completely dissolve the zinc nitrate. After complete dissolution of

zinc nitrate, 0.2 M of sodium hydroxide solution was added carefully drop-

wise along the sidewalls of the solution vessel with the solution under

continuously stirring. The reaction was allowed to proceed for 2 hr after

complete addition of sodium hydroxide. After completion of reaction, the

solution was allowed to settle overnight. The supernatant liquid was then

carefully decanted and the remaining solution was centrifuged at 10,000 X g

for 10 minutes. The nano particles that resulted were then washed three times

using distilled water. Washing was carried out to remove the by-products and

any starch bound to the nano particles. The washed nano particles were dried

overnight at 80 C. Drying helps in the complete conversion of Zn (OH)2 to

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ZnO. Similarly, copper oxide nano particles were also prepared using copper

sulphate and sodium hydroxide as precursors and soluble starch as stabilizing

agent. The prepared nanocomposites were nanoencapsulated by method as

given in section 3.12. The nanoencapsulated nanocomposites were finished on

the fabric and the antibacterial activity was analyzed.

3.15 DEVELOPMENT OF MEDICAL TEXTILE PRODUCTS

The nanoencapsulated nanocomposites finished cotton fabric with

the maximum antibacterial activity was chosen for the medical product

development. The products developed were surgical mask, medical napkin,

and surgical cap. The developed products were then tested for their efficiency

by analyzing the antibacterial activity of the used products. The antibacterial

activity of the used fabric both after washing and sterilization were tested and

the results were compared by field trials where a team of three health care

professionals validated the developed products after usage. The construction

details of the medical products are presented below. The antibacterial

activities of the developed products were assessed by standard methods

AATCC 147 test method.

3.15.1 Surgical Mask

(i) Fabric Dimension

Length - 9”

Width - 7.5”

(ii) Steps of Construction

1. The pattern was placed over nano particle finished cotton

fabric and the pattern was transferred on to the fabric.

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2. Fabric strips of half-inch width were folded into half and

sewn around the edges of the masks to make the edge strong

and to make it look even.

3. Small cords of elastic were attached to the top and bottom

seams of the masks so as to adjust the mask to the face of the

wearer.

Figure 3.3 Surgical mask

3.15.2 Medical Napkins

(i) Fabric Dimension

Length - 12”

Width - 7”

(ii) Steps of Construction

1. The nano particle finished cotton fabric was cut in to a

rectangle of 12” X 7”.

2. The four sides of the fabric were folded and stitched evenly to

get a napkin.

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Figure 3.4 Medical Napkins

3.15.3 Surgical cap

(i) Fabric Dimension

Length -27’

Width -27”

(ii) Steps of Construction

1. The finished fabric was cut in to 24 inches in diameter.

Folded over the edges of the fabric 1/2 an inch and ironed.

2. Hemmed the fabric circle all the way around, tucking the raw

edges under as it is sewn. Left an opening of about 1 inch.

3. A piece of elastic measuring ¾ the of the head circumference

measurement was cut.

4. Threaded the elastic through the hem of the fabric through the

1-inch opening, gathering the fabric as it was stitched. Sewed

the two ends of the elastic together and hands sewed the

opening in the hem closed.

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Figure 3.5 Surgical cap