Wool Fabrics with Antibacterial Properties

Abstract

Wool fabric is a suitable medium for growing bacteria under favorable temperature and humidity conditions resulting in wool degradation, skin irritation or infections. Carboxylic groups were incorporated in wool polypeptide chains by grafting acrylic acid initiated chemically with hydrogen peroxide and metallic anions of Cu 2+ .The mechanism of grafting is suggested, and post-treatment with two antibiotics, Neomycin (Ne) and Tetracycline hydrochloride (Te), to obtain antibacterial fibers in relation to Gram-positive and Gram-negative microorganisms. This was confirmed by measuring the inhibition zone of treated wool fabric with the above mentioned antibiotic under various conditions. The modified fabrics showed different activities in relation to the microorganisms being dependent on the type and quantity of added biocide. Post-treated wool fabric displayed excellent bacteriostatic durability on fabric after multiple washing. FT-IR spectroscopy confirmed the ionic interaction between wool and the antibiotic due to the appearance of new bands at 1650 cm-1 corresponding to amide I and band at 1520 cm-1 attributed to amide II. Wool treated with the aforementioned method showed improvement in shrinkage. Changes in surface morphology were also observed.

Full text

RJTA Vol. 16 No. 3 2012
42
* Corresponding author. Tel.: (202) 0101556620; Fax: (202) 33322424
E-mail address: dreman411@yahoo.com (S.H. Abdel-Fattah)
Wool Fabrics with Antibacterial Properties
S.H. Abdel-Fattah
1
and E.M. El-Khatib
1*
1
National Research Centre, Textile research division, Dokki, 12622, Cairo, Egypt
ABSTRACT
Wool fabric is a suitable medium for growing bacteria under favorable temperature and
humidity conditions resulting in wool degradation, skin irritation or infections. Carboxylic
groups were incorporated in wool polypeptide chains by grafting acrylic acid initiated
chemically with hydrogen peroxide and metallic anions of Cu
2+
.The mechanism of grafting
is suggested, and post-treatment with two antibiotics, Neomycin (Ne) and Tetracycline
hydrochloride (Te), to obtain antibacterial fibers in relation to Gram-positive and
Gram-negative microorganisms. This was confirmed by measuring the inhibition zone of
treated wool fabric with the above mentioned antibiotic under various conditions. The
modified fabrics showed different activities in relation to the microorganisms being
dependent on the type and quantity of added biocide. Post-treated wool fabric displayed
excellent bacteriostatic durability on fabric after multiple washing. FT-IR spectroscopy
confirmed the ionic interaction between wool and the antibiotic due to the appearance of
new bands at 1650 cm
-1
corresponding to amide I and band at 1520 cm
-1
attributed to amide
II. Wool treated with the aforementioned method showed improvement in shrinkage.
Changes in surface morphology were also observed.
Keywords: Wool Fabrics, Tetracycline, Neomycin, Acrylic Acid, Grafting, Absorption,
Scanning Electro Microscope, FTIR Spectroscopy
1. Introduction
Different studies have been found in the literature
dealing with chemical modification of wool fibers
to acquire distinguished properties and reliable
applications for various end uses. Wool fabrics
and wool garments provide an excellent
environment for microorganisms to grow because
of their large area and ability to retain moisture
which can deteriorate these materials.
Antimicrobial treatments are rapidly becoming
standard finishes for some categories of textile
products such as medical institutional and
hygienic uses (Purwar & Joshi, 2004).
Antimicrobial finishes prevent microbial attack on
wool and prolong their useful life (Gao &
Cranston, 2008). There are different ways to
prevent the attachment of microorganisms to fiber
surface, including aromatic halogen compounds,
organometalic salts, quaternary ammonium salts
(Ali et al., 2010), iodophores, phenols, urea and its
related compounds (i.e. formaldehyde derivatives)
amines (Lim & Hudson, 2003) and silver
nanoparticles (Abdel-Fattah et al., 2010).
Natural products such as chitin derivatives and its
protonated amino groups on glucose ring are also
used (Achwal, 2003). The aim of this study is to
develop an approach to imparting bioactive feature
to wool macromolecules by incorporating
functional groups, such as carboxylic, into fibers
prior to the treatment with appropriate antibiotics.
Of all such conditions, the graft polymerization is
of prime importance. In the current work, grafting
of wool with acrylic acid initiated chemically and
post-treatment with antibiotics is established.
2. Experimental
2.1 Materials
2.1.1 Fabric
Mill scoured 100% wool fabrics supplied by
Misr-company. (Medhalla El-Kubra) for spinning
and weaving was used for this study.

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43
2.2.2 Reagents
The main chemicals used in this study were:
Acrylic acid (AA), hydrogen peroxide, copper
sulphate pentahydrate, sodium hydroxide and
glacial acetic acid of reagent grade.; Neomycin
sulphate (Ne) and Tetracycline hydrochloride (Te),
all of pure grade and donated by Nile Company
for Pharmaceutical and Chemical Industries,
Egypt.
2.2 Technical Procedures
2.2.1 Pretreatment by Graft Polymerization
Graft co-polymerization reaction was performed
by introducing wool fabric in a medium
containing the monomer acrylic acid
concentrations (0.02-0.06) mol/l, copper sulphate
0.06 mol/l and hydrogen peroxide concentrations
(0.02-0.08) mequ/l using material to a liquor ratio
of 1:50. Erlenmayer stoppered flask was used for
this purpose. The flask containing the reaction
mixture was placed in a thermostatic water-bath at
60
°
C. The co-polymerization was allowed to
proceed for 30 minutes and the reaction mixture
was shaken occasionally. The graft samples
obtained were removed and washed thoroughly
with hot water to get rid of the homopolymer that
may be formed. The grafted samples were dried in
an oven at 105
°
C for 3 hours and weighed. The
extent polymerization was determined as follows:
Grafting %
=
Wg
-
W
0
-------------
W
0
Where: Wg is the weight of grafted wool
W
0
is the initial weight of the ungrafted
wool.
2.2.2 Carboxyl Content
The carboxyl contents of grafted samples were
determined according to Cirino method (Cirino &
Rowland, 1976).
2.2.3 Antibiotics Treatment
The antibacterial finishing baths were prepared by
treating wool fabrics with 2% (owf) of the
antibiotic at a liquor ratio of 1:25, and the pH
value was adjusted to pH 5. Treatment temperature
and time were 30°C and 45°C for 3 hours. After
the processes were run, the fabric was removed
and the amount of antibiotic sorption by wool was
estimated. The residual antibiotic in the bath was
measured with UV/vis spectrophotometer model
2401 pc. The λ
max
values of Neomycin (Ne) and
Tetracycline (Te) were determined at 256 and 274
nm respectively. The relationships between the
absorbance and concentration were established at
λ
max
for each antibiotic. The amount of antibiotic
taken up by wool was determined as the percent
exhaustion and calculated as follows:
Exhaustion %
=
C
a
-
C
r
x 100
-------
C
a
Where C
a
is the antibiotic concentration in blank
solution and C
r
is the residual antibiotic
concentration in the treatment bath containing the
substrate after treatment.
2.2.4 Antibacterial Test
The antibacterial properties were qualitatively
evaluated against Staphylococcus aureus ATCC
6538, a Gram positive bacterium, Escherichia coli
ATCC 2666 and Pseudomonas aeruginosa a Gram
negative bacteria according to AATCC test method
(100-1999). The zone size (mm) of inhibition of
each sample was determined taking the average of
three individual measurements.
2.2.5 Alkali Solubility
The alkali solubility of wool was tested in an
aqueous solution of 0.1 N sodimhydroxide for one
hour at 65°C using a wool-liquor ratio of 1:100.
Details of the experiment procedure adopted were
described according to (Harris, 1947).
2.2.6 Fabric Shrinkage
Fabric shrinkage was determined after one wash
cycle by measuring the fabric area according to
(AATCC test method 1977).
2.2.7 Fourier Transfer Infrared (FT-IR)
FT-IR spectra of grafted wool and post-treated
with antibiotic were recorded on a Perkin-Elmer
spectrum 1000 spectrophotometer over 4000-400
cm
-1
spectral range using the KBr disk technique.

RJTA Vol. 16 No. 3 2012
44
3. Results and Discussion
3.1 Tentative Mechanisms
Previous studies (Lohani et.al., 1958; Stein &
Guarnaccio, 1959) have disclosed that hydrogen
peroxide, together with metallic ions viz-Cu
+2
,
forms a very effective system capable of initiating
vinly graft polymerization onto various
macromolecules. The results indicate that 0.08
mequ/l of hydrogen peroxide gave maximum graft
yield at any concentrations of acrylic acid. The
results in Table 1 illustrate that at concentration of
acrylic acid 0.02 mol/l, 0.08 mequ/l hydrogen
peroxide and 0.06 mol/l copper sulphate, the graft
yield was 6.1%, at concentration of acrylic acid
0.04 mol/l, he graft yield was 10.0% and at
concentration of acrylic acid 0.06 mol/l, the graft
yield was 13.9% at the same conditions of the
treatments. It seems interesting to establish the
influence of such ions on grafting of wool fabric
with acrylic acid (AA) in presence of hydrogen
peroxide as the initiator. The following reaction
scheme is suggested representing wool by W-H
and monomer as M:
H
2
O
2
 H
+
+ HO
2-
(1)
Cu
2+
+ HO
2-
 Cu
+
+ H
2
O
•
(2)
H
2
O
•
+H
2
O
2

OH
•
+ H
2
O + O
2
(3)
W-H + OH
•

W
•
+ H
2
O (4)
W
•
+ M

WM
•
(5)
OH
•
+ M

M
•
- OH (6)
The tentative mechanisms suggested by the above
reaction scheme show that H
2
O
2
is converted to
•
OH and H
2
O
•
radicals in presence of Cu+ when
H
2
O
2
is present in excess over Cu
+
ions (eq. 1-3).
These radicals attack wool macromolecules
through abstracting hydrogen atom, giving rise to
wool macroradical capable of initiating grafting of
AA (eq.4.). Beside that grafting and homopolymer
chains are propagated through addition of
monomer molecules till the termination step (eq.
5-6).
Table 1. Effect of acrylic acid conc. (0.02-0.06
mol/l) on the graft yield % of wool
fabrics
Conc. of acrylic
acid (mol/l) Graft yield %
0.02
6.1
0.04 10.0
0
.06
13.9
Treatment conditions:Conc. of hydrogen peroxide
0.08 mequl/l, Conc. of copper sulphate 0.06 mol/l,
at 60
°
C for 30 minutes and liquor ratio 1:50.
3.2 Assessment of Antibiotic Addition
The degree of antibiotic addition to modified
fibers can be affected by various conditions,
particularly by the degree of grafting of acrylic
acid (AA) to wool, pH of Neomycin (Ne) and
Tetracycline (Te) are amphoteric in nature, their
sorption on wool is expected to be largely
dependent on the bath pH. Previous studies
illustrate that the isoelectric point of wool and
antibiotic are approximately pH 5 (Choi et al.,
2004).
It is evident from Table 2 that the initial wool has
only a slight quantity of antibiotic added due to
the presence of small quantities of carboxylic
groups (13.2%). Therefore, the grafted fibers
containing numerous carboxylic groups (35.4%)
tend to combine antibiotic much more. However,
their sorption at 30°C was somewhat less than at
45°C. Nevertheless, the sorption values are higher
than those of manufactured fibers such as
polyurethane and polyester (Bide et al., 1993;
Yuan et al., 2001). It is also obvious that higher
temperature generally enhances the sorption rate
to grafted wool (57.6%). These results suggest that
interaction such as hydrogen bonding plays a
greater role in antibiotic sorption, Figure 1
illustrate Chemical structures of antibiotics.
Tetracycline
Neomycin
Fig. 1. Chemical structures of antibiotics

RJTA Vol. 16 No. 3 2012
45
Table 2. Effect of treatment temperatures on the extent of antibiotic exhaustion % (Antibiotic concentration
2% (o.w.f.), 3hrs, L.R. 1:25 at pH 5) and Carboxyl content of untreated and treated wool fabrics
Graft yield % Type of modified
wool Carboxyl content
meq/100g wool Exhaustion %
30
°
C
45
°
C
- W-UNT. 13.2 20.8 27.2
6.1
W-PAA-Ne
W
-
PAA
-
Te
14.8
40.20
31.30
43.20
37.50
10
W-PAA-Ne
W
-
PAA
-
Te
18.8
47.30
37.20
50.70
42.30
13.9 W-PAA-Ne
W-PAA-Te
35.4 50.70
45.40 57.60
54.30
Where : W-UNT represents untreated wool
W-PAA-Ne represents wool grafted with acrylic acid and reated with neomycin
W-PAA-Te represents wool grafted with acrylic acid and treated with tetracycline
3.3 Some Properties of Grafted Wool Fabrics
with Acrylic Acid
3.3.1 Inhibition Zone
It is evident from the data in Table 3 that the
antibiotics used are characterized by quite biocide
effects on the Gram-positive and Gram-negative
microorganisms. This is determined by quite large
zones which reach 39 mm for the Gram positive
and 35.4 mm for the Gram negative. This may be
attributed to incorporation of carboxylic groups
which tend to combine with the antibiotics to
provide fibers with biocide properties and to
disrupt the cell membrane of microbes through the
physical and ionic phenomenon. It was also
noticed that there is a correlation between the
extent of exhaustion % and inhibit zone.
Table 3. Inhibition zone of untreated and treated wool
Graft yield % Type of modified
wool
Inhibition zones of growth (mm)
Staphylococcus
aureus
Escherichia
coli
Pseudomonas
aeruginosa
- W-UNT. Infected completely
Infected completely
Infected completely
6.1 W-PAA-Ne
W
-
PAA
-
Te
30
25
28
20
23
19
10.0 W-PAA-Ne
W
-
PAA
-
Te
35
32
30
25
30
22
13.9 W-PAA-Ne
W
-
PAA
-
Te
39
33
35
31
30
25
Where: W-UNT represents untreated wool
W-PAA-Ne represents wool grafted with acrylic acid and treated with Neomycin.
W-PAA-Te represents wool grafted with acrylic acid and Treated with Tetracycline
3.3.2 Washing Fastness of Antimicrobial
Activity on Wool
Table 4 shows the results of antimicrobial resistant
of wool samples grafted with polyacrylic acid (AA)
and treated with antibiotic (Te, Ne) after five
washing cycles in a washing machine according to
AATCC test method 61-1994. It is evident from
the results that ungrafted samples have no effects
on both Gram-positive and Gram-negative
organisms, whereas (Ne) and (Te) added to the
grafted samples show that antibacterial effects are
maintained for five washes. These results reveal
that strong ionic bonds between Neomycin or
Tetracycline and carboxylate anion on wool
macromolecules confer such as antimicrobial
function (Sun, 2001) depending on the type and
quantity of added antibiotic.
3.3.3 Alkali Solubility and Fabric Shrinkage
Previous studies (Abdel-Fattah et al., 1974;
Hebeish et al., 1974) found that alkali solubility of
wool before and after grafting indicates that

RJTA Vol. 16 No. 3 2012
46
grafting has occurred. Table 5 illustrates that the
degree of solubility decreased as the polymer yield
increased. This can be ascribed to the formation of
diffusion barrier of grafted chains for the
solubilizing agent to penetrate into the fibers. The
polypeptide chain of wool is protected.
Table 4. Inhibition zone of untreated and treated wool fabric after five washing cycles
Graft yield %
Type of modified wool
Inhibition zones of growth (mm)
Staphylococcus
aureus Escherichia
coli Pseudomonas
aeruginosa
- W-UNT. Infected completely
Infected completely
Infected completely
6.1 W-PAA-Ne
W
-
PAA
-
Te
27
23
24
18
20
13
10.0 W-PAA-Ne
W
-
PAA
-
Te
30
29
27
22
26
20
13.9 W-PAA-Ne
W
-
PAA
-
Te
29
26
31
27
22
20
Table 5. Alkali solubility and area shrinkage of grafted wool with acrylic acid (AA)
Substrate Graft
%
Alkali Solubility
%
Area Shrinkage
%
Untreated Wool
-
16
9.6
Poly acrylic acid
Grafted Wool
6.1 7.0 7.3
10.0
6.0
5.1
13.9
4.0
3.8
In Loheni et al (1958), felting shrinkage is found
to be a result of cuticles scales of wool that
overlap during friction or washing. Grafting of
wool with polymers leads to the coverage of these
scales and thus avoids shrinkage.
From the results presented in Table 4, it is clear
that the antifelting properties improved with the
increase of grafted PAA on wool.
3.3.4 Surface Morphology
The above result is also verified by observing the
scanning electron micrographs Figure2. SEM
images of untreated wool fabric are presented in
figure 2a. The images of wool fabrics treated with
poly AA-Ne are given in Figure 2b. The treated
samples had smoother surface in comparison with
untreated sample.
3.3.5 Fourier Transfer Infrared (FT-IR)
Spectra
Wool grafted with (AA) and untreated wool fibers
were investigated by infrared spectroscopic
analysis. Figure 3 indicates the following
characteristics. The bands at 1066 cm
-1
and 1760
cm
-1
correspond to carbonyl group stretching.
Appearance of a new band at 1650 cm
-1
amide I
corresponds to CO stretching. Furthermore, the
appearance of a band at 1520 cm
-1
amide II
corresponds to NH bending due to NH
2
deformation (i.e. CONH
2
). This indicates the
formation of ionic interaction between antibiotic
and carboxylate anion on wool macromolecules
(Lambert et al., 1987).
This may confirm that grafting with (acrylic acid)
and treatment with antibiotics produce some
changes in the characteristic bands of wool.
- Untreated woolen fabric b- Wool-poly AA-Ne
Fig. 2. Scanning electron microscope of a-
untreated fabric, b- wool-poly AA-Ne
(initiator H
2
O
2
-CuSO
4
)

RJTA Vol. 16 No. 3 2012
47
Wave number cm
-1
Fig. 3. IR. spectra of (A) utreated wool, (B) wool
treated with PAA (Te) and (C)wool
treated with PAA-Ne
4. Conclusion
Wool can be a suitable medium for growing
bacteria under favorable temperature and humidity
conditions resulting in wool degradation, skin
irritation or infections.
Carboxylic groups were incorporated into wool
fabric by grafting acrylic acid (AA) initiated
chemically with hydrogen peroxide and metallic
ions Cu
2+
and post-treatment with two antibiotics
Neomycin (Ne) and Tetracycline hydrochloride
(Te) to obtain antibacterial fibers in relation to
Gram-positive and Gram negative microorganisms
(Staphylococcus aureus, Escherichia Coli and
Pseudomonas aeruginosa). This was confirmed
by measuring the zone of inhibition treated wool
fabric with the above mentioned antibiotic under
various conditions. Higher temperature enhance
sorption rate to grafted with acrylic acid (AA)
wool. There is a correlation between the extent of
sorption percent and inhibition zone depending on
the type of added antibiotics.
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