The Influence of PVOH Concentration on the Structural Morphology

and Dimension of Electrospun Nanofibers

Erni Misran

1,2

, Basuki Wirdjosentono

1,3

, Nasrudin M. Noor

, Saharman Gea

1,3

, Mahyuni Harahap

1,3

and Suhut Alexander Situmorang

1,3

Cellulosic and Functional Materials Research Centre, Universitas Sumatera Utara, Medan, Indonesia

Department of Chemical Engineering, Faculty of Engineering, Universitas Sumatera Utara, Medan, Indonesia

Department of Chemistry, Faculty of Mathematics and Natural Science, Universitas Sumatera Utara, Medan, Indonesia

Deparment of Physics, Faculty of Mathematics and Natural Science, Universitas Sumatera Utara, Medan, Indonesia

Keywords: Electrospinning, morphology, polyvinyl alcohol, nanofibers

Abstract: The parameters applied in electrospinning process were the main factors to produce ultrafine nanofibers for

different target applications. In this study, the effect of polyvinyl alcohol (PVOH) concentration, from 12%

to 16% (wt) in distilled water, on the morphology and dimension of nanofibers was investigated. Scanning

electron microscopy (SEM) was used to analyze the morphology of PVOH electrospun nanofibers and

Image J analysis was used to calculate the dimension of fibers. From the results, 12% and 13% of PVOH

concentration produced bead shaped fibers. Meanwhile ultrafine nanofibers were produced from PVOH

concentration of 14%, 15%, and 16% (wt). The diameter of ultrafine fibers increased with the increase in

PVOH concentration.

1 INTRODUCTION

Electrospinning technique, with its simplicity setup

of syringe pump, needle, and collector only (Figure

1), has attracted significant interest among

researchers to fabricate fibers with diameters

ranging from microscale (10 m) to nanoscale

(<1000 nm) (Zhuo et al. 2008). Moreover, this

method provide higher surface area to volume ratio

compared to other methods, i.e. template synthesis,

self-assembly, phase separation and drawing

techniques (Abunahel et al. 2018). Electrospun

nanofibers have been applied to various applications

including tissue engineering, drug delivery system,

wound dressing, textile industry, cancer treatment

and the fabrication of new radiation shielding

material (Mirjalili and Zohoori, 2016).

Basically, the process of electrospinning uses

high voltage power supply, so there is a surface

charge at the end of the needle tip where the

polymer solution is held by its surface tension. Due

to the disturbance in the polymer surface, droplets

with spherical shapes called "Taylor zone" are

produced in the initiation of electrospinning process.

Then, a jet of polymer solution is ejected from the

tip of the needle to the collector. As the jet travels

through the air, the solvent evaporates and ultrafine

fibers are collected on the surface of the target (Teo

and Ramakrishna, 2006). The properties of spun

fibers can be controlled with three important

parameters; (i) the parameters of solution, which

include the concentration, molecular weight, surface

tension, conductivity, and volatility of polymer

solution; (ii) processing parameters, such as applied

voltage, liquid flow rate, and distance of the needle

to the collector; and (iii) processing environment

like temperature and humidity (Harahap 2018).

Figure 1 Electrospinning set up.

Misran, E., Wirdjosentono, B., Noor, N., Gea, S., Harahap, M. and Situmorang, S.

The Inﬂuence of PVOH Concentration on the Structural Morphology and Dimension of Electrospun Nanoﬁbers.

DOI: 10.5220/0010613800002775

In Proceedings of the 1st International MIPAnet Conference on Science and Mathematics (IMC-SciMath 2019), pages 577-580

ISBN: 978-989-758-556-2

577

There are more than 50 different polymers that

have been reported to have undergone successful

electrospinning. One of them is PVOH, a water-

soluble polymer, which can also be electrospun from

its aqueous solution phase (Lu et al. 2006). Many

studies have reported the influence of concentration

on the morphology of fibers, but there has not been

any literature data available reporting the diameters.

Hence, we aim to study the effect of PVOH

concentration to the morphology of electrospun

nanofibers, as well as their diameters.

2 EXPERIMENTAL

2.1 Materials

The material used in this study was PVOH powder,

Mw = 60,000 g/mole fully hydrolyzed, purchased

from Merck, Darmstadt, Germany. Before used,

PVOH was dried at 80 °C for 5 h in a vacuum oven

to remove the moisture content. Distilled water was

used as a solvent for PVOH.

2.2 Solution Preparation

PVOH solution with various concentration of 12%,

13%, 14%, 15%, and 16% (wt) was prepared under

reflux condition for 2 hours at 80 °C. After the

polymer was homogeneously mixed, the reaction

was put to stop and the solution was allowed to cool

with continuous stirring until it reached room

temperature. The solution was stored no more than

three days prior to use for electrospinning.

2.3 Electrospinning Process

The electrospinning process was carried out by

horizontal electrospinning (basic series

electrospinning unit Brand NLI, Nanolab

Instruments Sdn Bhd, Malaysia) at room

temperature. The condition was set-up as follow: (i)

disposable 18-G syringes; (ii) voltage was 15 kV;

(iii) polymer solution feed rate was 0.2 mL/hour;

(iv) needle tip-to-collector distance was 15 cm; and

(v) the speed of collector was 115 rpm. Ultrafine

fibers were collected on aluminum foils. The mat

fibers were dried in a vacuum oven at 40 °C for 3 h

to remove residual water and stored in a desiccator

containing silica gel.

2.3 Characterization

2.3.1 Scanning Electron Microscopy

The morphology of the samples was analyzed by

using a scanning electron microscopy (SEM) Hitachi

TM3030 (JEOL, Ltd., Tokyo, Japan). The sample

was coated with a thin layer of gold before analysis

to reduce charging. The diameter of the fibers was

calculated by using Image J software analysis.

3 RESULTS AND DISCUSSION

3.1 The Morphology

The concentration of the polymer solution is one of

the parameters controlled in the electrospinning

process. It has a big influence in the formation of

fibers. Low concentration (<1 Pa.s) has been

reported to form sprays instead of fibers. In this

condition, bead forms were also produced.

Meanwhile, fine fibers would be produced with

higher concentration of polymer solutions (Yang et

al. 2007).

In this study, PVOH solution dissolved in

distilled water was able to undergo electrospinning.

The fiber formation is illustrated in Figure 2. During

the process, there were no clogs at the tip of the

needle. Nonetheless, the morphology of PVOH

electrospun nanofibers were not the same for each

concentration used. SEM images for PVOH

nanofibers with concentration of 12%, 13%, 14%,

15%, and 16% (wt) are presented in Figure 3. At the

concentration of 12% and 13% many beads were

produced. While, concentration of 14% produced

smooth fibers. The morphology of the fibers became

smoother with higher concentration (15% and

16%). Polymer concentration was the main factor

that affected the final morphology of fibers. If the

concentration of polymer was too high, the

electrospinning process could not be done due to

high viscosity. However, low concentration would

produce bead form fibers (Sener, Altay and Altay,

2011).

The dimension of nanofibers (Figure 3) in this

study was calculated from the fiber images in SEM

results by using Image J software. PVOH

electrospun nanofibers had diameters of 108 nm,

100 nm, 130 nm, 129 nm, and 133 nm for the

concentration of 12%, 13%, 14%, 15%, and 16%

respectively (Figure 4). The higher the concentration

of PVOH polymer solution, the higher the diameter

of spun fibers. However, this result contradicted

IMC-SciMath 2019 - The International MIPAnet Conference on Science and Mathematics (IMC-SciMath)

578

other studies that reported higher concentration or

viscosity of polymer solution produced smaller

diameter of spun fibers (Misran et al. 2020).

Figure 2 The formation of electrospun nanofibers.

Figure 3 SEM images for electrospun nanofibers: (a) 12%

PVOH, (b) 13% PVOH, (c) 14% PVOH, and 15% PVOH.

Figure 4 PVOH electrospun nanofibres dimensions with

various concentration of 12%, 13%, 14%, and 15% (wt).

4 CONCLUSION

Polyvinyl alcohol (PVOH) nanofibers were prepared

by electrospinning technique. In this study the

concentration of PVOH varied from 12% to 16%

(wt). At low concentration (12% and 13%) bead

fibers were produced. While higher concentration

(14%, 15% and 16%) produced fine nanofibers. The

diameter of PVOH electrospun nanofibers increased

from 108 nm to 133.6 nm with the increase in

concentration of PVOH concentration from 12% to

16% respectively.

ACKNOWLEDGEMENT

The authors would like to thank the Rector of

Universitas Sumatera Utara and the Ministry of

Higher Education, Research and Technology

Indonesia for the research fund from DRPM 2019

PDUPT scheme with contract number

28/UNS.2.3.1/PPM/KP-DRPM/2019.

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