2C13
Effect of ZnO nanoparticles on the electrospinning of poly(vinyl alcohol) from aqueous
solution: influence of particle size
T. Jamnongkan, R. Shirota, S. K. Sukumaran, M. Sugimoto* and K. Koyama
Graduate School of Science and Engineering, Yamagata University, Yonezawa, 992-8510 Japan.
* E-mail: sugimoto@yz.yamagata-u.ac.jp
organic materials, such as good processability, andAbstract
We have investigated the electrospinning ofaqueous

PVA

solutionswithsuspended

ZnO

inorganic materials, such as thermal stability andchemicalresistance.

Someresearchers

havenanoparticles. ZnO nanoparticles of three different

successfully

diameters (20, 70 and 100 nm) were used in the study.

composited with inorganic materials such as silica,Interestingly, we found that increasing the diameter ofgold and silver for biomedical applications. One suchsuspended ZnO nanoparticles was accompanied by amaterial

isZnO

especiallydecrease in the diameter of the electrospun fibers.

nanoparticles.

ZnO

not only exhibits superior

FTIR indicated that the ZnO nanoparticles wereantimicrobial activity, but is also nontoxic to humans

merely suspended in the aqueous PVA solution

and is environmentally friendly [3]. Owing to these

without any chemical bonding between the ZnO

reasons, we expect that nanofibers made from PVA

nanoparticles and the PVA chains. Shear rheometry ofwith

the suspensions indicated that, over the relevant range

antibacterial properties and hence be potentiallyof shear rates, all of the samples exhibited essentiallyattractive for applications such as wound dressings.

produced

addedZnO

nanofibers

innanoparticles

fromthewillPVA

formofpossess

Newtonian behavior. However, the viscosity increasedwith a decrease in the diameter of the ZnO

Experiment

nanoparticles. We consider that the effect of theWe have investigated the electrospinning ofnanoparticles on the diameter of the electrospun fibers

PVA solutions with suspended ZnO nanoparticles ofis through their effect on the viscosity of thethreesuspension.

electrospinning process, the electrical voltage in thedifferent

particlediameters.

Duringtherange of 10-25 kV was applied and the tip-to-collector
Introduction
Electrospinning has received a lot ofdistance was varied between 5 and 15 cm for eachattention in recent years because it is relatively simple

at 0.006 mL/min. All electrospinning was performed

to produce continuous fibers from a variety ofat room temperature and the relative humidity waspolymers using this technique. The diameter of themaintained at 30%.

applied voltage. The feed rate of the solutions was set

produced fibers can range from a few nanometers toseveral micrometers [1]. For biomedical applications,human safety concerns are of paramount importance.

Results and discussion
We found at a given electric field strength,

Poly(vinyl alcohol) (PVA), being biocompatible andthe fiber diameter progressively decreased with anbiodegradable, is especially attractive and has been

increase in the diameter of the added ZnO particles, as

successfully used in several biomedical applications

can seen in the Fig. 1. To understand of this behavior,[2]. In recent years, materials that combine organic

We investigated the chemical structure of theand inorganic components have attracted great interest

electrospun fibers by using FTIR. The IR spectra ofas they exhibit advantages characteristic to boththe suspensions did not exhibit any additional peaks.

Fig. 1. The average diameter of the electrospun fibers

Fig. 2. Variation of the viscosity of the PVA solutions(df) as a function of the diameter of the ZnO

with ZnO particles of three different sizes with shear

nanoparticles for different electric field strengths.

rate.

This indicates that no chemical reaction has
occurred between the ZnO nanoparticles and the PVA
polymer chains in the aqueous medium [4].
We

also

investigatedtheshear-rate

dependent viscosity of the four samples used for
producing the electrospun fibers and relate the flowcharacteristics to the behavior seen in electrospinning.
We first determine the approximate apparent shear
rate at the wall of the needle using,Conclusions
Using electrospinning, nonwoven fiber matswere successfully fabricated from an aqueous solutionof PVA and suspensions of ZnO nanoparticles in PVA
aqueous solutions. Surprisingly, we found that anincrease in the diameter of the nanoparticles led to adecrease in the diameter of the corresponding
electrospun fiber. The shear viscosity increased with adecrease in the diameter of the suspended nanoparticle
in spite of using constant nanoparticle weight(1).

fractions in preparing the suspensions. We believe thisis the shear rate at the wall of the needle, Q

increase in the shear viscosity can explain theis the volumetric flow rate (fixed at 0.006 mL/min in

observed increase in the fiber diameter with awhere,

this work) and r is the radius of the needle (0.30 mm).
The calculated shear rate is approximately 5 s-1.
Hence, we measured the viscosity of the samples for

decrease in the particle size.
References

shear rates between 1-500 s-1 and the data is shown in1. H. Yoshimoto, Y.M. Shin, H. Terai, and J.P.

Fig. 2. Note that the measured viscosity is essentially

Vacanti, Biomaterials, 24, 2077 (2003).

independent of the shear rate in this range, indicating
thattheflow

behavior

isNewtonian.

More

2. Y.T. Jia, J. Gong, X.H. Gu, H.Y. Kim, J. Dong, andX.Y. Shen, Carbohyd. Polym., 67, 403 (2007).

interestingly, the viscosity increases with a decrease

3. K.R. Raghupathi, R.T. Koodali, and A.C. Manna,in the diameter of the ZnO nanoparticles.

Langmuir, 27, 4020 (2011).

Using Fig. 2 and Fig.1, we show propose thatthe effect of the particle size on the fiber diameter for
all of the electric field strengths investigated isprimarily through their effect on the viscosity.

4. T.Jamnongkan, R. Shirota, S.K. Sukumaran, M.
Sugimoto and K. Koyama, Polym. Eng. Sci., To be
published, 2013.