1 Study of Surface Modification of Wool Fabrics Using Low Temperature Plasma.

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1 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: , Tehran, Iran. * shahidish@yahoo.com 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 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 80 0C for 80 min and then washing was conducted twice with distilled water at 80 0C 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 O 2, N 2 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 3 0C min -1 up to 80 0C, holding for 30 min at 80 0C. 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. O 2 gas was used for 7 min Sample was placed on the Anode. O 2 gas was used for 7 min Sample was placed on the Anode. N 2 gas

3 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 nm. (The wavelength of Blue dyes is 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 N 2 and O 2 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.

4 Figure1: SEM images of treated and untreated samples 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 O 2 plasma treatment and 3400 cm -1, corresponding to N-H group after N 2 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 O 2 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 O 2 -cathode LTP treated samples.

5 5 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 O 2 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

6 6 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. 5-References: [1] R.Molino, J.P.Espinos, F.Yubero, P.Erra, A.R.Gonzalez-Elipe, XPS analysis if down stream plasma treated wool: Influence of the nature of the gas on the surface modification of wool, Applied Surface Science 252 (2005) [2] W.Xu, G.Ke, J.Wu, X.Wang, Modification of wool fiber using steam explosion, European Polymer Journal, [3] T.Wakida, S.Cho, S.Choi, S.Tokino, M.Lee, Effect of low temperature plasma treatment on color of wool and nylon 6 fabrics dyed with natural dyes. Textile Research Journal, 68(11), 1998, [4] F.Osenberg, D.Theirich, A.Decker, J.Engemann, Process control of a plasma treatment of wool by plasma diagnostics, Surface and Coating Technology (1999) [5] G.Roberts, F.Wood, A study of the influence of structure on the effectiveness of chitosan as an anti felting treatment for wool, Journal of Biotechnology, 89 (2001) 297 [6] R.A.Difelice, J.G.Dillard, D.Yang, Chemical and nanomechanical properties of plasma polymerized acetylene on titanium and silicon, International Journal of Adhesion & Adhesives 25 (2005) [7] D.Sun, G.K.Stylios, Fabric surface properties by low temperature plasma treatment, Journal of Material Processing Technology, 173 (2006) [8] T.Wakida, S.Tokino, S.Niu, M.Lee, H.Uchiyama, M.Kaneko, Dyeing properties of wool treated with Low Temperature Plasma under atmospheric pressure, Textile Research Journal, 63(8) (1993) 438 [9] L.Kravets, S.Dmitriev, A.Gilman, A. Drachev, G.Dinescu, Water permeability of poly (ethylene terphethalate) track membranes modified by DC discharge plasma polymerization of dimethylaniline, Journal of Membrane Science, 263 (2005) 127. [10] H.Gulec, K.Sarioglu, M.Mutlu, Modification of food contacting surfaces by plasma polymerization technique. part 1: Determination of hydrophilicity, hydrophobicity and surface free energy by contact angle method, Journal of food Engineering 75 (2006) 187. [11] F.Huang, Q.Wei, X.Wang, W.Xu, Dynamic contact angles and morphology of PP fibers treated with plasma, Polymer Testing, 25 (2006) 22. [12] P.Chaivan, N.Boonyawan, P.Suanpoot, T.Vilaithong, Low temperature plasma treatment for hydrophobicity improvement of silk, Surface & Coating Technology 193 (2005) 356. [13] J.Yip, K.Chan, K.Sin, K. Lau, Low temperature plasma treated nylon fabrics, Journal of Material Processing Technology, 123 (2002) 5. [14] P.Chaivan, N.Pasaja, D.Boonyawan, P.Suanpoot, T.Vilaithong, Low temperature plasma treatment for hydrophobicity improvement of silk, Surface & Coating Technology 193 (2005) 356. [15] M.Ghoranneviss, B.Moazzenchi, S.Shahidi, A.Anvari, A.Rashidi, Plasma Processes and Polymers, 3 (2006) 316. [16] Y.Chun Liu, Y.Xiong, D.Lu, Surface Characteristics and antistatic mechanism of plasma-treated acrylic fibers, Applied Surface Science, 252 (2006) [17]C.Nastase, F.Nastase, A.Dumitru, M.Ionescu, I.Stamatin, Composites: Part A, 36 (2005), [18] A.Choukourve, A.Grinevich, J.Hanus, J.Kousal, D.Slavinska, H.Biederman, A.Bowers, L.Hanley, Thin Solid Films, 2005 [19] M.Carmen, A.Almazan, J.I.Paredes, M.Perez-Mendoza, M.Domingo-Garcia, F.J.Lopez-Garzon, A.Martinez-Alonso, J.M.D.Tascon, Journal of Colloid and Interface Science 287 (2005) [20] I.Errifai, C.Jama, M.Le Bras, R.Delobel, L.Gengember, A.Mazzah, R.De Jaeger, Surface and Coating

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