E. DRESVYANINA et al.: COMPARISON OF ELECTROSPINNIN39–42G AND WET-SPINNING METHODS FOR ...
COMPARISON OF ELECTROSPINNING AND WET-SPINNING
METHODS FOR THE PRODUCTION OF CHITOSAN-BASED
COMPOSITE FIBERS
PRIMERJAVA MED ELEKTROSPINIRANJEM IN METODO
MOKREGA SPINIRANJA ZA PROCESIRANJE KOMPOZITNIH
VLAKEN NA OSNOVI HITOZANA
Elena Dresvyanina1, Alexandra Yudenko2, Inna Lebedeva1, Pavel Popryadukhin1,
Irina Dobrovolskaya1, Vladimir Yudin1, Pierfrancesco Morganti3
1Peter the Great St. Petersburg Polytechnic University, Polytechnicheskaya 29, 195251 St. Petersburg, Russia
2Saint-Petersburg State University of Industrial Technologies and Design, B. Morskaya 18, 191186 Saint-Petersburg, Russia
3University of Campania "Luigi Vanvitelli", Viale Abramo Lincoln n. 5, Caserta, Italy
elenadresvyanina@gmail.com
Prejem rokopisa – received: 2017-07-03; sprejem za objavo – accepted for publication: 2017-10-03
doi:10.17222/mit.2017.116
The influence of chitin nanofibrils on the production of chitosan-based fibers is described in the article. The chitosan-based
fibers and composite fibers were prepared from an aqueous solution of 2-% acetic acid using the coagulation method. The
incorporation of 0.1–0.3 % of mass fractions of CNs into the chitosan matrix contributed to an increase in the mechanical
properties of the composite fibers. The chitosan nanofibers were spun with electrospinning from a 70-% acetic-acid aqueous
solution of chitosan containing 10 % of mass fractions of PEO and 1–30 % of mass fractions of CNs. The introduction of CNs
into chitosan solutions accelerates considerably the quality of nanofibers at the electric field and decreases the amounts of
defects in them. The optimal concentration of CNs for producing defect-free chitosan nanofibers was 20 % of mass fractions.
Keywords: chitosan, chitin nanofibrils, wet spinning, electrospinning
V ~lanku avtorji opisujejo vpliv hitinskih nanovlakenc na procesiranje vlaken na osnovi hitozana. Vlakna na osnovi hitozana in
kompozitna vlakna so pripravljali iz 2 % vodne raztopine ocetne kisline s koagulacijsko metodo. Vnos od 0,1 do 0,3 masnih
odstotkov hitinskih nanovlakenc (angl.: CNs) v hitozansko matriko je prispeval k izbolj{anju mehanskih lastnosti kompozitnih
vlaken. Hitozanska nanovlakna so spinirali (zapredli) z elektrospiniranjem iz 70 % vodne raztopine ocetne kisline hitozana, ki je
vseboval 10 masnih % PEO (angl.: Poly Ethilen Oxide) in 1–30 masnih % CNs. Vnos CNs v hitozansko raztopino je znatno
izbolj{al kvaliteto nanovlaken v elektri~nem polju in zmanj{al koli~ino napak v njih. Ugotovljena optimalna koncentracija CNs
je bila 20 masnih odstotkov pri procesiranju hitozanskih nanovlaken brez napak.
Klju~ne besede: hitozan, hitinska nanovlakenca, mokro in suho me{anje
1 INTRODUCTION
Chitosan, a derivative of the natural polysaccharide
chitin, exhibits a biocompatibility, biodegradability,
bactericidal activity and absence of toxicity. Due to such
properties, chitosan-based materials find a lot of appli-
cations in medicine. Two methods such as wet spinning
and electrospinning are used for the preparation of
chitosan-based materials. Wet spinning is widely used
for polysaccharides.1 Chitosan is a typical polysaccha-
ride and fiber preparation from chitosan is possible only
with the precipitation of the solution followed by
washing and drying.1,2 Recently, the interest in fibers
with a diameter of tens or hundreds of nanometers has
grown. These nanofibres can be obtained with electro-
spinning. The materials based on chitosan nanofibers can
be used as tissue-engineering drugs consisting of a
polymer matrix and stem or somatic cells.3
The aim of this work is to compare the influence of
chitin nanofibrils on the wet spinning of microfibers and
electrospinning of nanofibers, as well as on their struc-
tures and properties.
2 EXPERIMENTAL PART
Chitosan with DD = 92 %, Mw = 190 kDa, PD = 1.6748
(Bioprogress, Russia) and chitosan with DD = 86 %,
Mw = 210 kDa, PD = 1.0752 (Fluka Chemie, Bio
Chemika line) were used for preparing chitosan fibers.
Chitin nanofibrils (CNs, Mavi Sud s.r.l, Italy) and PEO
(Unioncarbide, Mw = 9 × 105) were used as the filler for
obtaining the bioresorbable composite fibers and
improving their formation.
The chitosan microfibers as well as composite
microfibers modified with CNs were prepared from a
2-% acetic-acid aqueous solution of chitosan using the
coagulation method.1,2 The chitosan nanofibers were
prepared by electrospinning from a 70-% acetic-acid
aqueous solution of chitosan containing PEO and CNs.4
Rheological studies were performed on a Physica
MCR 301 rheometer (Anton Paar) at 20 °C. The elec-
trical conductivities of chitosan solutions and their
mixtures were determined with a Seven Compact S230
electrometer (Mettler Toledo Co., Switzerland). Sur-
Materiali in tehnologije / Materials and technology 52 (2018) 1, 39
UDK 620.1/.2:67.017:621.315.614 ISSN 1580-2949
Original scientific article/Izvirni znanstveni ~lanek MTAEC9, 52(1)39(2018)
face-tension values were found via a drop-shape-analysis
tensiometer (DSA 4) (KRUSS, Germany) using the
hanging-drop method. The structures of the fibers and
nanofibers were investigated with a Supra 55VP
scanning electron microscope. Measurements of the
mechanical properties of the produced fibers were
carried out on an Instron 5943 testing machine.
3 RESULTS AND DISCUSSION
Dependencies of the viscosity () on the shear rate
(
) for chitosan solutions have a non-linear behavior. In
the chitosan solution without the filler (Figure 1), a
decrease of viscosity was observed at the shear rate of
10 s–1 or more. Increasing the concentration of the
polymer in the solution leads to an increase in the
effective viscosity. The optimal concentration of chitosan
in the solution was 6–6.5 % for sample 1 and 4 % for
sample 2. Fibers with the best mechanical properties
were prepared with the 213 kDa chitosan sample and
PD = 1.0752, whose fibers have a strength of 220±18 MPa
and Young modulus of 0.9±0.12 GPa.
The threshold value of the shear rate, at which the
dependence of  (
) becomes non-linear, shifts to smaller
values with an increasing content of CNs (Figure 1). For
the mixture containing 20 % of mass fractions of the
chitin filler, the dependence of  (
) becomes linear over
a wide range of shear rates. Generally, the decrease in
the viscosity upon an increase in the shear rate is related
to the destruction of the initial structure of the polymer
solution and the creation of a newly oriented structure,
which indicates a transition from the isotropic state to
the anisotropic one. An increase in the CN content in the
chitosan solution is accompanied by an increase in the
viscosity, which is especially noticeable at low shear
rates. This indicates a good interaction of the CNs with
chitosan macromolecules and the formation of the
cluster structure of the filler. Thus, the wet spinning of
composite chitosan/chitin fibers at a very low CN
content (<1 %) should be close to the production of
pure-chitosan fibers.
The strength of the chitosan fibers (without a filler)
grows considerably with an increase in drawing up to
 ~ 50 % (Figure 2). Further drawing does not affect the
fiber strengthening. The strength of the composite
chitosan/chitin fibers containing a small quantity
(0.05–0.3 % of mass fractions) of the filler increases
monotonically with the drawing up to  ~ 120 %. An
increase in the content of CNs in the composite fibers
above 1 % of mass fractions significantly changes the
nature of the () dependence. An increase in the
strength ceases at  ~ 20 % just as it does in the case of
unfilled chitosan fibers. The incorporation of 0.1–0.3 %
of mass fractions of CNs into the chitosan matrix con-
tributed to an increase in the strength (Figure 3) and
Young modulus of the composite fibers due to the
additional orientation of the chitosan macromolecules on
the CN surfaces.2
E. DRESVYANINA et al.: COMPARISON OF ELECTROSPINNIN39–42G AND WET-SPINNING METHODS FOR ...
40 Materiali in tehnologije / Materials and technology 52 (2018) 1,
Figure 3: Dependences of the tensile strength of chitosan/chitin com-
posite fibers on the content of CNs
Figure 1: Dependences of viscosity on the shear rate for chitosan
solutions with different contents of CNs
Figure 2: Dependences of the tensile strength of chitosan and chito-
san/chitin composite fibers on orientation drawing  for different
contents of CNs
The preparation of the fibers from chitosan with
electrospinning is very difficult. It is known that to spin
chitosan-based nanofibers, water-soluble fiber-forming
polymers, such as PEO, PVA or methyl cellulose, are
added to the solution.3
It was shown that the electrical conductivities of
chitosan solutions and liquid mixtures containing PEO
are 2–4 mS/cm, that is, three to four orders of magnitude
higher than the values for polymers with good spinning
abilities in electric fields (aliphatic copolyamides and
PVA).4 The introduction of PEO causes a slight decrease
in the electrical conductivity of a solution with a chitosan
concentration of 7 % of mass fractions, but has almost no
effect on the electrical conductivities of solutions con-
taining small amounts of chitosan (3 % or 4 % of mass
fractions). The surface-tension coefficients of the chito-
san solutions with concentrations of 3–4 % of mass
fractions remain practically the same after the addition of
small amounts of PEO. At the same time, the addition of
PEO to the 3- and 4-% of mass fractions of chitosan
solutions has no effect on surface-tension coefficients 
.
For a 5-% of mass fractions of chitosan solution, the
surface-tension coefficient increases with an increase in
the PEO content. Note that these values are higher than
the values for the solutions of PEO and aliphatic
copolyamide, for which 
 is ~30 N/m.
All these studies were carried out using chitosan
sample 1 that was optimal for electrospinning. To im-
prove the process, the CNs were incorporated into the
chitosan solution as well. The conductivity of the mixed
solution likewise increases insignificantly with the addi-
tion of 1–10 % of mass fractions of CNs with respect to
chitosan.4
From the above data, it follows that the surface-
tension value exhibits a jump-like decrease when the
concentration of CNs in the pure solution is 1 % of mass
fractions, while an increase in the concentration of CNs
leads to a slow decrease in the surface tension. However,
for the solutions with the same concentrations of CNs
and chitosan and an addition of 10 % of mass fractions
of PEO, we can observe the disappearance of the jump-
like decrease, while the level of the surface tension
becomes constant, regardless of the concentration of
CNs.
The addition of nanofibrils to the PEO-containing
chitosan solution, on the one hand, increases the visco-
sity and, on the other hand, considerably increases its
dependence on the shear rate, relative to the solutions
free of chitin nanofibrils.
The incorporation of CNs into chitosan solutions
stabilizes the electrospinning of nanofibers and makes it
possible to reduce the content of PEO in nanofibers.
After the introduction of less than 20 % of mass frac-
tions of PEO, the amounts of defects (drops, micro-
spheres) in nanofibers increase considerably. Moreover,
these defective nanofibers are formed only at a very low
polymer-flow rate, while an increase in this rate leads to
the formation of even larger drop-like defects, causing a
substantial decrease in the fraction of nanofibers.
After the introduction of CNs into the chitosan solu-
tion containing 10 % of mass fractions of PEO, defect-
free structures of nanofibers may be obtained (Figure 4).
4 CONCLUSIONS
Chitosan-based fibers and composite fibers were
prepared from an aqueous solution of 2-% acetic acid
with the coagulation method. The incorporation of
0.1–0.3 % of mass fractions of CNs into the chitosan
matrix contributed to an increase in the strength and
Young modulus of the composite fibers. The chitosan
solutions containing CNs exhibited the necessary
rheology characteristics, preserving the laminarity of the
jet in the coagulation bath after the solution flows
through the die hole.
The introduction of CNs into chitosan solutions
accelerates considerably the quality of the nanofibers at
the electric field and decreases the amounts of defects in
them. It was found that the optimal concentration of CNs
for producing defect-free chitosan nanofibers is 20 % of
mass fractions.
The obtained fibers may be used as the matrices for
cell-replacement technologies and tissue engineering as
well as the materials for wound dressings and hemostatic
material.
Acknowledgment
The authors are grateful to the Russian Science
Foundation Grant ¹ 14-33-00003 for the financial
support.
E. DRESVYANINA et al.: COMPARISON OF ELECTROSPINNIN39–42G AND WET-SPINNING METHODS FOR ...
Materiali in tehnologije / Materials and technology 52 (2018) 1, 41
Figure 4: Micrograph of a material obtained via the electrospinning of
a 4-% chitosan solution containing 10 % of mass fractions of PEO +
20 % of mass fractions of CNs
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E. DRESVYANINA et al.: COMPARISON OF ELECTROSPINNIN39–42G AND WET-SPINNING METHODS FOR ...
42 Materiali in tehnologije / Materials and technology 52 (2018) 1,