Relationships Between Solution Conductivity and Current of Jet in Electrospinning Baturalp Yalçınkaya1, Funda Cengiz-Çallıoğlu1, Fatma Yener 2, Oldrich Jirsak2 1 2
Süleyman Demirel University, Eng.&Arch. Faculty, Textile Eng. Dept., 32260, Isparta, Turkey
Technical Univ. of Liberec, Textile Eng. Faculty, Nonwoven Dept., Liberec 46117, Czech Republic
[email protected]
Abstract In this research, relationships between Poly (vinyl alcohol) (PVA) solution conductivity and current of jet in electrospinning were analysed. It was also determined the effects of PVA polymer and sodium chloride (NaCl) salt concentration on the conductivity of solution and current of jet during electrospinning. According to the results, conductivity of solution and current of jet increased with PVA and NaCl concentration. It was observed that there is a strong relationship between solution conductivity and jet current. During the experiments three different jet regimes were observed such as stable jet, stable jet with polymer drops and multiple jets. And fiber morphology was affected from type of jet regime.
Keywords: PVA, conductivity, jet regime, current, nanofiber.
Objective The aim of this study is analysing the relationships between PVA solution conductivity and current of jet in electrospinning. Also, effects of PVA polymer and NaCl salt concentration on the solution conductivity and jet current were investigated. For all solutions, jet regimes were analysed and associated with fiber morphology. Material and Method PVA (M=13x104) was used as polymer and distilled water used as solvent. Solutions were prepared at various concentrations such as 9-12-15 wt % PVA. Also the solution has 12 wt % PVA concentration, includes various concentration of NaCl salt such as 0,1-0,2-0,5-1 wt %. PVA and NaCl concentrations were chosen from previous works [1]. Then, conductivity of PVA solution was determined. All solutions were spun by needle electrospinning process and current apparatus was connected to collector of this method.
Current test was done with HP Hewlett Pack 34401A multimeter. The electric current of solution jet during the electrospinning was determined by ohmic resistor (9841Ω) in series between collector and ground. Electric current was calculated using Ohm’s law. Pokorny and Jirsak was suggested measurement method of jet current during electrospinning firstly. They measured the current via oscilloscope for understanding the theoretical description of electrospinning [2]. As can be seen in Table 1, the same process parameters were applied during the electrospinning process.
Table 1. Spinning conditions of PVA polymer solution
Voltage (kV)
Distance(cm)
25
16
Needle Dia. Outer/Inner (mm) 0,6 (0,33)
Feed Rate (ml/h)
Temp. (°C)
Relative Humidity (%)
0,5
25
30
Digital camera was used to observe jet regimes during the electrospinning process. And then, SEM images were taken by Phenom FEI to analyse fiber morphology.
Result and Discussion Table 2 shows all results of solution conductivity, jet current and type of jet regime.
Table 2. The results of solution conductivity, electric current of jet and type of jet regime.
Sample
Conductivity (mS/cm)
9 % PVA
1,49
12 % PVA
1,65
15 % PVA
1,98
12 % PVA 0,1 % NaCl 12 % PVA 0,2 % NaCl 12 % PVA 0,5 % NaCl 12 % PVA 1,0 % NaCl
5,6 10,2 20,8 33,0
Jet current (micro A) 0,815411
Type of Jet Regime a
2,140455
a
3,057792
a
3,669351
a
3,74792
b
3,873204
c
4,892468
c
From the results of Table 2, solution conductivity and jet current increase with PVA polymer and NaCl salt concentration. Therefore we can say that current of jet is directly related with solution conductivity. This result is compatible with literature [3].
During the electrospinning process, three types of jet regimes were observed; (a) stable jet regime (b) stable jet regime with polymer drops and (c) multiple jet. Various jet regime pictures and fiber morphology incident to these jets are given in Figure 1.
a)
b)
c)
Figure 1. Various type of jet regimes and fiber morphology incident to these jets (x1.000) a) 12 % PVA (25 kV) b= 12 % PVA + 0.5 % NaCl (20 kV) c= 12 % PVA + 1.0 % NaCl (25 kV).
As Samatham et al indicated that each jet regime has different fiber morphology. Stable jets with polymer droplets have beads formation on the surface while multiple jet regimes have thicker fiber diameter [4]. Our results are in the same direction with Samatham’s work.
Conclusion In conclusion, there is a strong relationship between solution conductivity and jet current during electrospinning. Solution conductivity and jet current increase with PVA polymer and NaCl salt concentration. Also, three different types of jet regimes were observed and associated with fiber morphology.
References [1] Dao, A.T. and Jirsak, O., 2009. Effect of Sodium Chloride on the Needle Electrospinning of Poly (vinyl alcohol), Nanocon 2009, 20-22 October, Roznov pod Radhostem, C.R. [2] Pokorny, P. and Jirsak, O., 2010. Measurement of Electric Current During Electrospinning, ‘TexSci10’, 6–8 September, TU, Liberec, C.R. [3] Bhattacharjee, P.K., Schneider, T.M., Brenner, M.P., McKinley, G.H. and Rutledge, G.C., 2010. On the Measured Current in Electrospinning, J Appl Phys, 107, 044306. [4] Samatham, R., Kim, K.J., 2006. Electric Current as a Control Variable in the Electrospinning Process, Polymer Engineering and Science, 46, 954–959.
