FABRICATION OF COMPOSITE NANOFIBER YARN PRODUCED FROM PA AND WOOL NANOPARTICLES

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1 FABRICATION OF COMPOSITE NANOFIBER YARN PRODUCED FROM PA AND WOOL NANOPARTICLES Ali Akbar GHAREHGAHAJI 1, Arezoo RAJABIMEHR 2, Ali ZADHOUSH 2 1 Department of Textile engineering, Amirkabir University of Technology, Tehran, Iran 2 Department of Textile Engineering, Isfahan University of Technology, Isfahan, Iran aghaji@aut.ac.ir Abstract: Producing the yarn from nanofibers has received great attention in recent years and several techniques have been developed in this concern. While composite nanofibres are mainly produced from CNT, there is not any reported work about production of nano fibrous composite yarn with nanopowder of natural fibers such as wool so far. This study aims at improving the hygroscopic properties of nylon 6 nanofibers by introducing wool fiber nanoparticles (WFNP) into PA nanofibres and electrospinning of composite yarns with various contents of WFNP. Also, some physical, mechanical and morphological properties of composite nanofibers and yarns were evaluated. Results shows that WFNP content in the composite PA nanofibre yarn has a governing effect on the mechanical properties of composite yarns such as tenacity, breaking elongation, work of rupture and elastic modulus. Increasing the WFNP content in the composite PA nanofibre yarn could also improve the moisture absorption of nylon nanofibers. Key Words: wool fiber nanoparticles, nylon 6 nanofibers, composite naofibre yarn, mechanical properties, morphology 1. Introduction Natural fibers have played an important role as textile materials from ancient times and still are widely used in the modern textiles industry for their unique properties as high quality textile materials. The whole part of all natural fibers cannot be used during spinning process as spun yarns, because of their short length. Consequently, natural fibers such as wool, silk, cotton or hemp are wasted during processing and final usages. A new way of reusing these fibers has large marketing potential because of their excellent intrinsic properties. Since the protein powder could keep the original properties of the materials without destroying the microstructure, it has been widely applied in modern industries and some hi-tech related fields are developed due to some unique properties [1-3]. To improve some of the synthetic polymers properties such as dye ability, elastic recovery, warmth retention property and moisture retention production of wool powder has been developed. In order to use the discarded protein resources, most of the researchers developed keratin films. These films could be used as packaging materials and replace the daily-used synthetic packaging films which are very difficult to get degraded in nature [4,5]. Electrospinning has emerged as an ideal route for the production of aligned nanotube based nanofibrous nanocomposites. This technique involves applying a high voltage to a polymer solution in a syringe and when the voltage applied reaches a certain threshold limit, the polymer solution overcomes surface tension and ejects a fine jet of liquid from the tip of the needle and deposits on the collector [6,10]. A novel technique of manufacturing continuous yarn by using two oppositely placed metallic needles connected to positive and negative voltage is presented by Li et al. In this technique, fibers coming out of the two needles combine to build in a yarn, which is wound on a cylindrical collector rotating at a high speed [11-13]. Composite nanofiber yarn produced from PA 6 and WFNPs was characterized with SEM, TEM, Fourier transform infrared (FT-IR) and mechanical, physical and morphological properties of composite nanofiber yarn were also examined.

2 2. Experimental 2.1. Materials Using a retrieving waste wool, wool powder was prepared through physical method. After this process, particle size was examined by particle size analyzer which showed that the particles were smaller than 300 nm in diameter. Nylon 6 is used for the synthesis of Wool fiber nanoparticles (WFNPs) based nanofibrous nanocomposites via electrospinning. Nylon is one of the most widely used commercial polymer fibers with a wide range of applications. Nylon 6 solution of 12 wt% concentration was prepared by dissolving the polymer in 98% formic acid. Wool fiber nanoparticles (WFNPs) were dispersed to disrupt possible agglomerate using an Ultrasonic Homogenizer model UP200H (Hielscher) operating at 24 khz. Different masses of WFNP were weighted and added to certain quantities of formic acid. These mixtures were stirred for 1h and kept in an air tight bottle to prevent evaporation of formic acid for a certain period of time. Then, specific amount of Nylon 6 were added to this mixture and stirred for 24h until the polymer was uniformly dissolved in the solvent and viscosity of the solution reached its optimum level. Before the electrospinning process, solutions container WFNPs and Nylon 6 in formic acid sonicated. The final solutions produced contained varying concentrations of WFNP from 0 to 7 wt% in 12 wt% Nylon 6 solution Electrospinning setup Flat-tipped, stainless steel needles were installed in opposite direction at a distance of about 18 cm. Polymer solutions were pumped to needles by two syringes infusion pump. Typical operating regimes were flow rates of 0.24 ml/h. Applied voltages for the two needles was 11kV. When voltages were applied to the needles fed with polymer solution, jets were ejected Characterization SEM analysis The samples were sputter-coated with gold-palladium. Fibers and yarns were examined using a (Phlips XL-30) scanning electron microscopy at accelerating voltage of 5 kv TEM analysis A Transition electron microscopy (TEM) was utilized to qualitatively determine the size distribution and structure of WFNPs in the composite nanofiber on Cu grids for samples of randomly collected fibers, The TEM Philips CM120 was used with an accelerating voltage of 120 kv FTIR analysis Fourier Transform Infrared (FT-IR) spectrometer was carried out on WFNPs, Pa nanofibers and Composite yarn of WFNPs/PA6 by BOMEN (MB-series 100), Hartman & Braun, Canada Mechanical characterization Mechanical properties of composite nanofiber yarns were measured by tensile tester Zwick Measurement of moisture regain

3 Moisture regain of the samples was tested under standard conditions (RH 65% and 20 C). The moisture regain of the samples was defined as follows: Moisture regain (%) = (W2 W1)/W1 100 where W1 and W2 stand for the dry weight and conditioned weight of the samples, respectively. 3. Results and discussions 3.1. FTIR analysis 3.1. FTIR analysis FTIR spectra of composite nanofiber yarn produced from PA and 7% WFNP in concentration, PA nanofiber and wool powder are shown in Fig. 1. There are several absorption bonds in the curves. The bonds 3425,3309 cm -1 is due to the stretching vibration of OH groups in PA and wool fiber and NH group in NHCO- respectively, the bonds at 2922,2852 cm -1 is attributed to the stretch vibration of C-H groups in polyamide chain amino acids of protein polymer. The spectra of the composite nanofiber yarn exhibit absorbing bonds around 1641 (Amide Ι, C=O stretching), 1538 (Amide ΙΙ, secondary N-H bending) and 1254 cm -1 (Amide ΙΙΙ, C-N stretching), which indicate the characteristic vibration bonds of Fig. 1. FTIR spectra of (a) WFNPs,(b) PA s nanofibers, (c)wfnp/pa 6 nanofibers polyamide and protein of wool. Other absorbing bonds around 1428, 1370, 1171, 1074,668 and 584cm -1 were also found in the structure of composite yarn from nanofibers. So, the FTIR spectra of the WFNP/PA6 composite nanofiber yarn show the characteristic absorbing bonds of both wool fiber and PA 6, which indicate that the mixture does not influence the chemical bonds of both the wool fiber and PA 6 and no new steady bonds are formed by simple physical mixing.

4 7th International Conference - TEXSCI 2010 September 6-8, Liberec, Czech Republic 3.2. Morphological characterization Fig. 2 shows some morphological aspects of nanomaterials resulted from SEM images of the nanofibers collected from spinning triangle and the body of final produced yarns containing various concentrations of WFNPs from 0 to 7 wt% in respect to 12wt% nylon 6 solution. Morphological analysis of these images shows that, since the amount of WFNPs concentration is increased, the surface morphology of the fibers become more rougher and morphology of the fibers become rougher and less smooth because nano powder was only partly dispersed in the nanofibers matrix. (a) (b) (c) (d) (e) (f) Fig. 2. (a-c) are SEM images of nylon 6 nanofibers with uniform diameter. (d-f) SEM images of aligned nylon 6 nanofibers containing 7% WFNPs in 12 wt% nylon 6/formic acid at 11 kv voltage, 18cm syringe needles distance and 22cm syringe and collector distance less smooth because wool nano powder was only partially dispersed in the nanofiber matrix. It has been confirmed that, dispersing the WFNPs inside the fibers body and orienting them along the axis of the fibers were reduced. TEM images can show the WFNPs inside the body of the electronspun nanofibers. Fig. 3 shows TEM images of aligned nylon 6 nanofibers containing 7 wt% WFNPs in 12 wt% nylon 6 solution. By these images, some of the nanoparticles inside the body of the fibers were observed which indicate that dispersion hasn t occurred completely. The existence of some crack and uneven areas on the surface of nanofibers probably were due to different absorbance and repellent in the protein and PA polymers. Poor dispersion is attributed to stress resulted from agglomeration of WFNPs at high load concentration and high loading of WFNPs that change the surface tension and viscosity of polymer composite solution.

5 Fig. 3. TEM image of nylon 6 nanofibers containing 7% WFNPs in 12 wt% nylon 6 solution Mechanical properties Assessment of mechanical properties indicates that with an increase in the powder content, the composite nanofibers yarn will become more and more weakened. This is attributed to the addition of wool powder, which has disturbed the regular and uniform internal structure of PA nanofibers yarn. When WFNPs content in the structure of PA 6 yarn was increased, because of moisture absorbed by fibers, it is probable that the fibers were swollen and consequently amount of the stress concentration sites were increased and tensile strength was dropped Moisture regain: The results of this work showed that Moisture absorption of WFNP/PA 6 is greater than that of PA 6 nanofibers. The moisture regain (Table 1) of the nanofibers of PA 6 increased obviously from 5.73% of the pure PA 6 to 12.44% of composite nanofiber yarn with 7 wt% nanoparticles. 4. Conclusions Table 1. Moisture absorption of WFNPs/PA nanofibers at 20 C and, 65% R.H. sample Moisture regain (%) 12% PA % WFNP/PA % WFNP/PA % WFNP/PA % WFNP/PA Producing the yarn from nanofibers has received great attention in recent years and several techniques have been developed in this concern. While composite nanofibres are mainly produced from CNTs, there is not any reported work about production of nano fibrous composite yarn with nano particles of natural fibers such as wool so far. This study could achieve production of a new generation of composite nanifiber yarns from wool nano particles. The results show that: - Converting the wool fibers into nano particles in powder form is feasible by appropriate mechanical processing. Particle size analyzer confirmed nano size of the resultant powder.

6 - The yarns from nanofibers containing 12% W/W polymer and (0-7)% WFNPs in formic acid were spun. Experiments showed that higher contents of WFNPs disturbs the electrospinning process. - Study on the effect of using of wool fibre nanoparticles with various concentrations on morphology of nanofibers is carried out by manipulation of Scanning Electron Microscope (SEM) micrographs and Transmission Electron Microscopy (TEM). The results confirms the morphological changes in the interstructure and surface of PA nanofibers. - Fourier Transform Infrared (FTIR) is carried out on nano materials. Results showed that no probable structural change has occurred in WFNPS. - Assessment of moisture regain of composite yarns revealed the effect of WFNPs content, i.e. hygroscopic properties of nylon 6 nanofibers is improved by introducing higher amounts of wool fiber nanoparticles (WFNPs). - Results shows that WFNP content in the composite PA nanofibre yarn has a slight detrimental effect on the mechanical properties of composite yarns such as tenacity. References 1. Hu, J. Y., Li, Y.,Chang, Y. F., Yueng, K. W., Yuen, C. W., Physicochem. Eng., Vol. 300, 2007, pp Xu, W., Wang, X., Li, W., Peng, X., Liu, X., Wang, X., Macromol. Mater. Eng., Vol. 292, 2007, pp J. R. Barone, W. F. Schmidt, C. F. E. Liebner, J. Appl. Polym. Sci., Vol.97, 2005, pp Xushan, G., Yan, T., Ying, C., Shuangyan, H., Huashuai, C., Mengjuan, Q., Mel. Int., Vol. 4, 2006, pp K. Yamauchi, H. Hojo, Y. Yamamoto, T. Tanabe, Mater. Sci. Eng. C, 23, 2003, pp Haung, Z. M., Zhang, Y. Z., Kotaki, M., Ramakrishna, S., Composite Sci. & Tech., 2003, Vol.63 No.15, pp Babel, A., Li, D., Xia, Y. N., Jenekhe, S. A., Macromol., Vol. 38, 2005, pp Subbiah, T., Bhat, G. S., Tock, R. W., Parameswaran,S., Ramkumar, S. S., J. of Appl. Polym. Sci., Vol. 96, 2005, pp , 9. Greiner, A., Wendorff, J. H., Angew. Chem. Int. Ed., Vol. 46, 2007, pp , 10. Bazbouz, M. B., Stylios, G. K., J. of Applied Polymer Science, Vol. 107, 2008, pp , 11. Pan, H., Li, L., Hu, L. and Cui, X., Polymer, Vol. 47, 2006, pp Jose, M. V., Steinert, B. W., Thomas, V., Dean, D. R., Abdalla, M. A., Price, G., Janowski, G. M., Polymer, Vol. 48, 2007, pp Bazbouz, M.B., Stylios, G. K., Eur. Polym. J., Vol. 44, 2008, pp. 1-12