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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
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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