EFFECT OF CONCENTRATION AND SALT ADDITIVE ON TAYLOR CONE STRUCTURE. Baturalp YALCINKAYA, Fatma YENER, Funda Cengiz-Çallıoğlu, Oldrich JIRSAK

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1 EFFECT OF CONCENTRATION AND SALT ADDITIVE ON TAYLOR CONE STRUCTURE Baturalp YALCINKAYA, Fatma YENER, Funda Cengiz-Çallıoğlu, Oldrich JIRSAK Nonwoven Department, Faculty of Textile Engineering, Technical University of Liberec, Studentska 2, 46117, Czech Republic, Abstract: One of the most important parameter is Taylor cone structure on the roller electrospinning method such as number of Taylor cone and life of jet. During electrospinning process, these parameters are affected directly spinning performance or efficiency. In this work we prepared Polyurethane / Dimethylformamide (DMF) polymer solutions and their tetraethylenamonyumbromur (TEAB) salt solutions. Then, we spun solutions via roller electrospinning. During the process we recorded roller surface and determined Taylor cone number and life of jet (in second). As a result we understood that life of Taylor cones are depended on number of Taylor cone. Whilst Taylor cone numbers were high, the life of jet had been low. Key words: Roller electrospinning, PU, TEAB, Taylor cone structure. 1. INTRODUCTION The phenomenon of electrospinning is an issue of a tug of battle solution between electrostatic and capillary forces. When a small volume of conductive liquid exposed to an electric field, the shape of liquid starts to deform from the shape caused by surface tension alone. As the voltage is increased the electrostatic force starts to over comes the surface tension and a cone shape begins to form with convex sides and a rounded tip. This approaches the shape of cone called as Taylor cone [1]. Recently, a new technology has been developed by Jirsak [2] that is based on highly productive jet creation from free liquid surfaces by self-organisation. This technology is called roller electrospinning under the brand name of Nanospider. The cylinder rotates in a polymer solution tank. The electrostatic field organised between the cylinder and a grounded collector enables the self-organisation of jets along the upper surface of the cylinder and, hence, fibers collect on the supporting material. There are lots of parameters that affect the electrospinning process. These can be divided as system and process parameters. Viscosity, concentration, net charge density (conductivity), surface tension of the polymer fluid and molecular weight can be shown as system parameters. Applied voltage, flow rate of polymer solution, distance between capillary end and collector, ambient parameters and motion of collector can be shown as process parameters. In this work firstly effect of concentration and additives on the number of cones was investigated. Then number of Taylor cone was associated with life time of a cone. Polyurethane (PU) was used as polymer. The aim to choose PU is, it has a good spinnability on roller electrospinning system and Polyurethane (PU) is thermoplastic polymer having excellent mechanical properties and water insolubility. PU is a pure polymer and has many application area such as filtration, medical application, biosensors, protective clothes, antimicrobacterial fibers, etc. [3-7]. 2. EXPERIMENTAL In this work polyurethane (PU) polymer, molecular weight is 2g/mol was used as a polymer and dimethylformamide used as a solvent. Solutions were prepared at various concentrations such as

2 wt % PU and tetraethyleneammonium bromide (TEAB) salt was added in different concentrations such as wt %. All solutions were prepared under the same conditions and measured conductivity of solutions than spun to nanofibers via roller electrospinning method. In this method, there is a roller which is connected to high voltage supplier and top of the roller there is a collector which was grounded. Taylor cones are created on the roller surface towards to collector (Fig 1). Fig. 1: Schematic diagram of roller electrospinning method Digital camera was used to observe these Taylor cones and life of jet on the roller surface in course of spinning (Fig. 2). Fig. 2: Picture of Taylor cones on the roller surface Optimum process parameters such as roller speed, roller length, distance between the electrodes, voltage etc. were applied during the spinning process (Table 1). Table 1: Process parameters of roller electrospinning Mechanical Parameters Process Parameters Environmental Parameters Roller Length (cm) Roller Speed (rpm) Supporting Material Speed (cm/min) Distance Between Electrode (cm) Voltage (kv) Humidity (%) Temperature ( C) 14,

3 Number of Cones (#) Conductivity (ms/cm) , Brno, Czech Republic, EU 3. RESULT AND DISCUSSION Polymer solution properties have an important role on resultant polymer. Adding salt increases the number of ions in the polymer solution as a result conductivity increases. The result of conductivity of PU solutions are shown in Fig ,5 1,5 %15 PU %17,5 PU %2 PU Fig. 3: Conductivity of PU polymer solutions. Conductivity has a positive effect on spinnability of fiber due to higher electrostatic field. Concentration and addition salt affected the number of cones and life time of one jet. Number of cones increased proportionally with concentration and conductivity as indicated in Fig %15 PU %17,5 PU %2 PU Fig. 4: Number of cones vs. concnetration. There is a direct relation between number of cones and fabric throughput. When the number of cone increases on the same area of roller, the amount of material which is transporting to collector increases. More material means higher throughput. However when the amount of feeding rate not change and number of cones increase, the life time of jet decreases due to finishing of polymer solution source on the surface of roller very quickly (Fig. 5).

4 Life of Jet(sec) , Brno, Czech Republic, EU %15 PU %17,5 PU % 2 PU Table 2. Spinning performance of PU solutions. Fig. 5: Life of jet vs. concentration. PU Concentration (%) TEAB concentration (%) 15,3125,468,6836 Spinning Performance (g/min/m) 17,5,9563,98 1, ,189 1,2235 1,3394 Fabric throughput (spinning performance) is tabulated in Table 2. 15% wt. PU was not able to spin on roller electrospinning system while 17.5 and 2% wt. had very low performance that was not calculated. On the other hand, adding salt increases spinning performance drastically. As we mentioned above spinning performance and number of cones are directly proportional while inverse proportional with life of jet. 4. CONCLUSIONS Roller electrospinning method depends on a wide range of independent and dependent parameters. Taylor cone number is one of the dependent parameter and in this study effect of polymer and additive concentration on life of jet and fabric performance was investigated. The Taylor cone number increase with salt and polymer concentration (conductivity) increase. A large quantity of Taylor cone is needed more polymer solutions on the roller surface. During process feed rate of polymer solution was kept constant. Consequently life of jet (in second) decrease with Taylor cone number increase. In addition fabric performance increase with Taylor cone number increases.

5 ACKNOWLEDGEMENTS This work was supported by Technical Universty of Liberec, Textile Faculty. The authors greatfully acknowledge to laboratory workers in Nonwoven Department for providing all device. LITERATURE [1] TAYLOR, S., "Disintegration of Water Droplets in an Electric Field". Proc. Roy. Soc. London. Ser. A, 1964, 28 (1382): 383. [2] JIRSAK O., SANETRNIK F., LUKAS D., KOTEK V., MARTINOVA L., CHALOUPEK J., "A Method of Nanofibres Production from a Polymer Solution Using Electrostatic Spinning and a Device for Carrying Out the Method". European Patent: 24, EP 1 ( ). [3] KIMMER, D., VINCENT, I., PETRÁŠ, D., LOVECKÁ,L., ZATLOUKAL, M., SLOBODIAN, P., OLEJNÍK, R., LANGER, J., TUNKA, M., ŠOUKAL, J., From Synthesis to Application. Polyurethane Nanofibers Developed in Spur a.s., Nanocon 29. [4] HAN, J.H., TAYLOR, J.D., KIM, D.S., KIM, Y. S., KIM, Y.T., CHA, G.S., NAM, H., Glucose Singh Biosensor with a Hydrophilic Polyurethane (HPU) Blended with Polyvinyl Alcohol/Vinyl Butyral Copolymer (PVAB) Outer Membrane, Sens. Actuators B, 27, 123, 384. [5] HAINS, N., FRISCIC, V., GORDOS, D., Testing Electrostatic Properties of Polyurethane Coated Textiles Used for Protective Clothing, Int. J. Cloth. Sci.Technol., 23, 15, 25. [6] YAO, C., LI, X., NEOH, K. G., SHI, Z., KANG, E. T., Surface Modification and Antibacterial Activity of Electrospun Polyurethane Fibrous Membranes with Quaternary Ammonium Moieties, 28, J. Membr. Sci., 32, 295. [7] GORJI, M., JEDDI, ALI. A. A., GHAREHAGHAJI, A. A., Fabrication and Characterization of Polyurethane Electrospun Nanofiber Membranes for Protective Clothing Applications, Journal of Applied Polymer Science, 212, Vol. 125,