P-8
Proceedings of the 3rd International Conference on the Frontiers of Plasma Physics and Technology (PC/5099)
1
Study of Surface Modification of Wool Fabrics Using Low Temperature
Plasma.
Sheila Shahidi *, Mahmood Ghoranneviss, Bahareh Moazzenchi, Abosaeed Rashidi
and Davood Dorranian.
Plasma Physics Research Center, Science and Research Campus, Islamic Azad
University, P.O.Box:14665-678, Tehran, Iran.
* E-Mail: [email protected]
Abstract
Modern textile treatments seek to obtain the optimum level of beneficial effect by modifying only
the fabric surface. Low Temperature Plasma (LTP) is nowadays an intensively investigated superficial
treatment of wool.
Owing to the selective modification of wool surface, LTP leads to the formation of new surface
group. Plasma treatment of wool is confined to the fabric surface, leaving the bulk properties unchanged.
In this work, plasma produced by DC glow discharge in a cylindrical glass tube evacuated up to 10-3
torr by mechanical pumps. The surface Characterization was performed using XRD, FTIR and SEM
imaging, so allowing the selection of treatment parameters for reproducible, efficient and stable surface
modification. The absorption time were utilized to analyze the result of the treated samples. The changes in
these properties are belived to be related closely to the inter-fiber/ inter-yarn frictional force induced by
LTP treatment.
This experimental work suggests that the changed properties induced by LTP can affect an
improvement in certain textile products.
1-Introduction:
Keratin fibers, like wool or human hair, can be considered as natural composite materials,
where keratinous protein is the main basic constituents [1]. Wool is high-quality protein
fiber and is widely used as a high-quality textile material [2]. It is well known that
surface characteristic of fibers play an important role in the functional and aesthetic
properties of their fabrics, and many surface modifications by chemical treatments are
able to improve textile properties [3]. Felting is an undesirable feature of woolen clothes.
It occurs as a result of the directionally dependent frictional coefficient of the wool fibers.
To reduce felting, this directional dependency must be reduced. Nowadays, this is done
by treating the wool in a chlorine-containing solution. During this treatment, the outer
surface of the wool, which mainly consists of approximately three-quarters protein and
one-quarter lipid, is etched [4, 5]. However, this procedure has to be replaced because of
environmental care [4]. Plasma pretreatments are environmentally benign and energyefficient processes for modifying the surface chemistry of materials [6-9].
Plasma treatment, as a clean, dry and environmental friendly physical technique, opens
up a new possibility in this field [10-15]. Plasma treatment can usually induce the
following processes: dehedrogenation and consequent unsaturated bond formation
trapped stable free radicals formation, generation of polar groups through post plasma
reaction, and generation of increased surface roughness through preferential amorphous
structure ablation processes [16].
In this research work, the surface of wool fabrics are etched and oxidized by the oxygen
in the plasma, this etching is necessary to improve the felting behavior of the wool.
2
2-Experimental:
2-1-Preparation of wool fabrics:
Wool plain woven fabrics (Iran Merinus Co, Iran) were used in this work. The fabrics
were weaved by 20 denier (1 denier = 0.1 g km-1) warp and weft yarns composed of 36
filaments. For sample preparation, size residue and contamination on the fabrics were
removed by conventional scouring processes, which the fabrics were washed with 0.5 gl-1
sodium carbonate and 0.5 gl-1 anionic detergent solution (dilution ratio to water =1:10) at
800C for 80 min and then washing was conducted twice with distilled water at 800C for 20
min and once at ambient temperature for 10 min.
2-2-LTP Treatment
The DC magnetron sputtering reactor was used to treat the wool fabrics, and nonpolymerizing reactive gases, such as O2, N2 and Ar were used to modify the wool surface.
In the reaction chamber, a sheet of wool fabric was placed on the anode or cathode.
Details of samples are shown in Table 1. Before the process started air and old gases had
to be pumped out by the vacuum pump, thus almost a vacuum level was created in the
reaction chamber. Afterwards, plasma gas was introduced into the reaction chamber.
Discharge voltage was 500V, discharge current was 200 mA and the inter-electrode
distance was 35 mm. The pressure remained at 0.02 Torr for the entire glow-discharge
period.
2-3-Characterization Tests:
The morphology of the LTP treated wool was observed using a scanning electron
microscope (SEM, LEO 440I). All the samples were coated with gold before SEM
testing. We evaluated wettability by measuring the time it takes for 4 distilled water
dropped on the fabric to absorb.
The functional groups on the surface of samples were examined using FTIR
spectrometer (Bomem MB-100, made in Canada).
For dyeing process, aqueous solutions, containing 3.0 wt. % of the dye were employed
for dyeing wool fabrics. The bath ratio was 1:100 (1 g of fiber in 100 ml of dye solution).
The following dyeing condition was adopted: Initial temperature 40 0C, followed by a
temperature increase of 30Cmin-1 up to 80 0C, holding for 30 min at 800C. 5 g/lit of acetic
acid for pH adjustment, were added for anionic dyeing processes. After dyeing, the
fabrics were rinsed with cold-hot-cold water and then dried at room temperature.
Table 1. Description of samples.
Sample
No1
No2
No3
No4
Description
Sample was placed on the cathode. Ar gas
was used for 7 min
Sample was placed on the cathode. O2 gas
was used for 7 min
Sample was placed on the Anode. O2 gas
was used for 7 min
Sample was placed on the Anode. N2 gas
was used for 7 min
3
Color intensities of the dyed fabrics were measured by using a UV VIS-NIR Reflective
Spectrophotometer, over the range of 350-500 nm. (The wavelength of Blue dyes is 380480 nm, so this area was chosen for investigation). And the reflection factor (R) was
obtained. The relative color strength (K/S value) was then established according to the
following Kubelka-Munk equation, where K and S stand for the absorption and scattering
coefficient, respectively [15, 16]:
K/S: {(1-R)2/2R}
3-Results and Discussion:
3-1-Scanning Electron Microscopy (SEM):
The SEM analysis of surface morphology reveals slight changes whish occur on the
surface of wool fibers as a result of plasma modification. The rising parameters of LTP
treatment (time and power) lead to a slight increase in these changes causing a rounding
of scales, microcracks, recesses and tiny grooves, all caused by the etching of the
material . SEM micrographs of wool fibers after plasma modification are shown in figure
1.
As It can be seen in Figure 1, the scale of samples which were put on the cathode were
destroyed more than other samples. It showed that by putting samples on the cathode the
rate of etching is increased and it can help to anti felting of wool fibers. For N2 and O2
plasma treatment, that, samples where put on the anode, minimal damage occurs to the
scale structure as a result of the glow discharge treatment.
The most important effect of LTP treatment of wool is the change in the character of the
wool fiber surface from hydrophobic to hydrophilic and anti felt.
Figure1: SEM images of treated and untreated samples.
4
3-2-FTIR:
FTIR was used to examine the functional groups of the corresponding samples
investigated in Fig 2. As shown in Fig 2, only slight increase in absorbance at 1720 cm-1
(C=O bond) after O2 plasma treatment and 3400 cm-1, corresponding to N-H group after
N2 plasma treatment can be noticed. [17-20]
After Ar plasma treatment that samples were placed on the cathode no significant difference
in the FTIR spectra between original and plasma-treated samples (curve (a), (d)).
Figure2: FTIR spectra of samples
3-3-Dye ability of wool samples:
As it can be seen in Figures 3, the reflection factor of dyed LTP treated samples were
less than dyed untreated sample.
The results show that the O2 and Ar-Cathode plasma treatment are more effective in
increasing the dye exhaustion of wool with anionic dye. Furthermore, the colors achieved
much more brilliant shades with the LTP treatment. As it can be seen the K/S value of
LTP treated samples is more than original one, however, this value is more for Ar and
O2-cathode LTP treated samples.
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Figure 3: Reflection spectroscopy of untreated and treated samples.
3-4-Water Drop test:
The quality of water repellency of the samples were evaluated by water drop test in
which drops of controlled size were placed at a constant rate upon the fabric surface and
the duration of the time required for them to penetrate to the fabrics were measured. The
results are shown in Table 2 in which the absorption times have been recorded for
different treated and original samples. As seen after LTP treatment the water absorption
time is much decreased. However this time is very low for O2 –cathode LTP treatment.
Table 2: Absorption time of treated and untreated samples.
Sample
Untreated
No1
No2
No3
No4
Absorption time
20 min
5 sec
1 sec
2 sec
3 sec
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4-Conclusion:
In this research work, the surface of wool samples were changed both physically and
chemically by using LTP treatment. The situation of wool samples in LTP reactor is very
important factor. By putting samples on the cathode and using oxygen as a working gas,
the wet ability and dye ability of wool samples were increased.
It is promising that, this technology which has been known for a long time and is being
used in different branches of industry, in the near future will conquer textile industry as
well.
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