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Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University – Suceava
Year IX, No. 4 - 2010

METHOD OF CARBON NANOTUBES DISPERSION

IN POLYMERIC MATRIX

Monica MURARESCU1, Dumitru DIMA1, Gabriel ANDREI1, Adrian CIRCIUMARU1

1University “Dunarea de Jos” of Galati, Domneasca Street 47, Romania,
monica.murarescu@ugal.ro

Abstract: In order to obtain better homogenous composite material, different carbon nanotubes
(CNTs) dispersion techniques in the polymeric matrix are very well known. Due to the strong
interactions between CNTs, the efficiency of these dispersion techniques is highly limited. The aim of
this paper is to present improvement techniques considered as new step in the global dispersion
process before the composite material final shape finalization. At this moment, it is very difficult to
carry out a classical dispersion from technological point of view. In this paper, more than the
acknowledged mechanical and ultrasonic dispersion method, the introduction of a genuine dispersion
technique is proposed; it refers to an external vibrant magnetic field able to determine a vibration
movement of CNTs covered by a molecular Fe (III) oxide. This external vibrant magnetic field is made
by using a permanent magnet involved in a rotational movement around its own axis and also
interacts with the individual CNTs own magnetic fields. The maintenance of a tensioned vibrating
state at the individual CNT level contributes to a good dispersion state preservation and increases the
connections and physical-chemical interactions hindering. The dispersion efficiency in a vibrant
magnetic field was studied using the comparative methods, correlating the electronic microscopy
analysis with the mechanical strength tests. With respect to the composite material obtained under
these conditions, a significant quality improvement as well as a mechanical strength increase was
observed.

Keywords: magnetic properties, composite material, polymer matrix composites.

Introduction

Carbon nanotubes (CNTs) utilization in the
polymeric matrix consists in the obtaining
process of some unique properties as a
main result of their nanometrical
dimensions.
Their unusual structure along with a
decreased density, a remarkable strength
and stiffness, followed by electrical
properties versatility contribute to a high
interest on their use as ingenuous
polymeric materials reinforcement. [1], [3]
The key element of this possibility consists
in the mechanic, thermic and electric
properties transmission from the CNTs to
the polymeric composite material. Hereby,
there are two problems that have to be

solved in order to bring substantially
improvement to the polymers material
properties along with carbon nanotubes
addition as fillers: the interfacial
connection and moreover, the optimum
CNTs individual dispersion in the
polymeric matrix. [2]
The polymer interfacial adhesion can be
substantially improved by the chemical
functionalization of the nanotube surface.
The influence of the chemical bond
between nanotubes and the matrix on the
interfacial adhesion was anticipated by the
molecular dynamics simulations. [1], [5]
The particles having nanometrical
dimensions present a large surface, with a
higher size degree than conventional fillers
surface. Their surface area actions as the

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University – Suceava
Year IX, No. 4 - 2010

transfer interface of the strains and it is
responsible in the same time for the strong
and natural CNTs tendency to make
agglomerates. These properties efficient
operation in polymers depends on their
homogenous dispersion process in the
matrix at the same time with the
agglomerates destruction process and their
wetting with polymeric substance.
Considering CNTs distribution process in a
polymeric matrix, these elements would
have to be evaluated: the nanotubes length,
their disorder, the volume ratio, the matrix
increased thickness, the attraction between
CNTs themselves.[4]
The usual particles dispersion in the
polymeric materials seems to be difficult
and finally ends with both phases
separation and agglomeration
phenomenon. It was demonstrated that
nanoparticles’ thermodynamically stable
dispersion in the polymeric liquid can be
successfully obtained for the systems
which lineal polymer radius of gyration is
bigger than the nanoparticle radius.
The dispersed nanoparticles expand the
lineal polymeric chains and the primarily
result is a polymer which radius of
gyration increases with nanoparticles
volume ratio. It was suggested the fact that
this process entropic disadvantageous is
balanced by an enthalpy gain due to the
increased number of molecular contacts
between the dispersed nanoparticles
surfaces in comparison with nanoparticles
surfaces in the phase separation case. [2],
[5] Even the dispersed state is
thermodynamically stable; it is difficult to
be obtained considering an inappropriate
processing strategy, this one being one of
the most important things referring to
CNTs dispersion process into lineal
polymers. [2], [6] Starting from a well-
determined target like nanotubes
dispersion, different work techniques are
proposed: ultrasonication, mechanical
stirring, etc.

Ultrasonication has a big energy local
impact but introduces small quantities of
shearing forces, so that this method is
appropriate only for matrix with very low
thickness and small volumes. The local
energy input leads to CNTs breakage,
decreasing their length. CNTs dispersion in
an adequate solvent (like: dimethylketone,
styrene) represents an appropriate way for
ultrasonication technique application in
order to obtain CNTs composite materials.
In this way, it would be allowed an
agglomerates separation due to the
vibration energy. [3],[6] Decreased
agglomerates dimensions can be easily
obtained by using CNTs functionalization
technique.
Mechanical stirring is a usual dispersion
method of particles in the liquid systems
and can be successfully used for
nanoparticles dispersion. The dispersion
result depends on the mixer shape and size
as well as stirring speed. After an intensive
CNTs stirring into the resin, they present
the natural tendency of agglomerating and
this flocculation phenomenon
experimentally observed is primarily
generated by the wearing contacts as well
as elastic coalescence mechanisms. [7]
Calendaring becomes a working obtaining
way of a good dispersion state. This
method is a usual well-known method of
microparticles dispersion in different
matrix, like: colouring agent for cosmetics
and paint. A major advantage of this
method, apart from the improved
dispersion results would be the efficient
manufacture of a diversified
nanocomposites range.
Other methods than the above supposed
techniques of some energy type
introduction in CNTs/polymeric matrix
mixing process that would be able to
realize an enthalpy/entropy optimum ratio.
Furthermore, a good dispersion can be
anticipated and realized in this way.

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University – Suceava
Year IX, No. 4 - 2010

Materials and methods

In order to obtain nanocomposite materials
with polymeric matrix we used an
unsaturated polyesteric matrix AROPOLTM
M105 TPB ASHLAND OLANDA –
ROTTERDAM, a largely used resin at
industrial level added with 1% catalyst 2-
ethyl-cobalt hexanoat. We used methyl-
ethyl ketone peroxide 2% as initial
catalyst. Multi-wall carbon nanotubes
(MWCNTs) were obtained from
Cheaptubes Inc. USA, having the
following characteristics: external diameter
8 – 15 nm, length 10 – 50 µm and purity
over 95%. It was realized a covering
process with a molecular layer of Fe2O3 in
accordance with a technology that
represent another scientific paper aim. In
order to present carbon nanotubes optimum
concentration value in the polyester matrix,
we considered three types of concentration:
0.10; 0.15 and 0.20%.
We carried out the dispersion process
considering a self-technology represented
by two different types of stirring, starting
with a mechanical one and followed by a
ultrasonic type of stirring (fig.1).

Fig.1 The dispersion by ultrasonication process

in polyester matrix

At the end of these two different types of
stirring, a dispersion process in a vibrant
magnetic field (fig.2) took place. We made
two experimental series coded with A and

B using these three types of concentration
for carbon nanotubes covered by a
molecular layer of Fe2O3. The samples
coded with B made by using three different
types of concentration are different from
the samples coded with A due to the fact
that the dispersion technology contains an
extra-phase represented by a
supplementary dispersion in a vibrant
magnetic field (fig.2).

Fig.2 The dispersion process of CNTs in
polyester matrix in a vibrant magnetic field

The samples made in accordance with
standards EN 63, ASTM D790-81, NFT
57-105 or NFT 51-001 from a dimensional
and 3 point flexural test point of view were
moulded in rubber matrices that were
previously made-up by flush cutting
procedure. After the samples were
extracted from the matrices, they were
dimensionally and chemically stabilized
using a thermal treatment in the oven at
278K for 8 hours. For each experiment we
used 10 samples for a statistically
interpretation. The samples were fixed at 3
points flexural test on a testing machine
“win TestTM Analysis – Testometric
materials testing machines, England”. The
machine working parameters are: working
speed – 2,500 mm/min, flexural load –
1,000N, span – 32,000mm.

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University – Suceava
Year IX, No. 4 - 2010

Results and Discussion

The testing results were plotted and shown
in the following shape (fig.3).
The experimental data at 3 points flexural
test for the two series coded A and B are
schematically presented in table 1.
It is easier to understand in this way the
experimental data interpretation in order to
justify the anticipated effect of an external
vibrant magnetic field at carbon nanotubes
dispersion technology.

3 point fle xural te s t

100

150

200

250

300

350

400

450

0 0,5 1 1,1 1,5 2 2,5 3 3,5

strain(% )

fo
rc

e(
N

)

Fig.3 Three points flexural test. The variation of
deformation plot (%) depending on the applied

force (N)

Table 1
Bending modulus values

Sample

Bending
Strength

@
Break

(N/mm²)

Bending
Modulus
(N/mm²)

Transv.
Rupture
Strength
(N/mm²)

A0,10% 103.90 4168.64 103.90
B0,10% 105.04 4728.29 105.09
A0,15% 105.25 4305.62 105.45
B0,15% 109.24 4500.66 109.61
A0,20% 110.40 4605.21 110.44
B0,20%

111.50 4805.25 112.50

It was observed a bending modulus and
other mechanical parameters increasing
with carbon nanotubes concentration
increasing. Moreover, at the same
concentration values it was observed an
increasing at B series in comparison with
A series that demonstrates the vibrant
magnetic field efficiency in the dispersion

process of carbon nanotubes in polyester
matrix. The increasing variation of
mechanical parameters at 3 point flexural
test is presented in table 2.
The highest value for bending modulus is
observed at the concentration of 0.1%.
This conclusion is explained by the fact
that the vibrant magnetic field efficiency is
quantified when the gaps between
nanotubes clusters are large.

Table 2
Mechanical parameters variation at 3 points

flexural test for the same version of B series in
comparison with A series

Conc.(
%)

Bending
strength
variation

(%)

Bending
modulus
variation

(%)

Transv.
rupture
strength
variation

(%)
0.10 1.08 11.83 1.13
0.15 3.65 4.30 3.79
0.20 0.99 4.16 1.83

At the highest concentration values, that
means 0.15% and 0.20%, the same
parameter variation maintains quasi-
constant; the explanation would be that
gaps decreasing have important impacts on
the vibrant magnetic field efficiency
concerning the dispersion process of
carbon nanotubes covered by a molecular
layer of Fe2O3. SEM analysis (fig.4)
confirms the experimental data obtained at
3 points flexural test; an improved carbon
nanotubes distribution at B series in
comparison with A series was observed.
In the samples of 0.10% and 0.15% from A
series we observed a stronger
agglomeration in comparison with the
sample of 0.20% of the same set. This
aspect is possible due to the equilibrium
established by the attractive forces energy
between the nanoparticles and the
dispersion forces energy for 0.20%
samples. In this case we made a
comparison on the adverse energetic state
for the dispersion forces considering the
samples of 0.10% and 0.15%
concentration. At B series, considering all

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University – Suceava
Year IX, No. 4 - 2010

concentration values, a superior
distribution at carbon nanotubes was
observed.

A0,1%

A0,15%

A0,2%

Fig.4 SEM analysis for A series samples of

0,10%, 0,15% and 0,20% concentration without
the vibrant magnetic field presence

B0,1%

B0,15%

B0,2%

Fig. 5 SEM analysis for B series samples of

0,10%, 0,15% and 0,20% concentration in a
vibrant magnetic field presence

Food and Environment Safety - Journal of Faculty of Food Engineering, Ştefan cel Mare University – Suceava
Year IX, No. 4 - 2010

From SEM analyses made by using
Quanta™ 200 Scanning Electron
Microscope (2006) we noticed that the
non-agglomerated state of the particles
from B series in comparison with A series
demonstrates the fact that the enthalpic
gain from the external vibrant magnetic
field leads to the bond breakage between
the nanoparticles participating in the
clusters formation. This phenomenon is
better observed at decreased concentration
values of carbon nanotubes covered by a
molecular layer of Fe (III) oxide. This is a
consequence probably due to the vibrant
magnetic field energy. It would be an
interesting topic to be focused on, but
considering the technological reasons we
analyzed only a single type of magnetic
stirrer.

Conclusions

The experimental data and the physical
analysis confirm the theory of an optimum
equilibrium existence between the
dispersed system enthalpy and entropy.
The mechanical, ultrasonic and external
electro-magnetic field energy that is
induced in the dispersed system due to
carbon nanotubes covered with a molecular
layer of Fe (III) oxide in the same time
contribute at this target. This aspect is
reflected by SEM analysis of the samples
in / without a vibrant magnetic field and
also by the flexural modulus and other
mechanical parameters increasing resulted
from three points flexural test.
In conclusion, we demonstrated that
another technological step introduction in
the dispersion process of carbon nanotubes
covered with a molecular layer of Fe (III)
oxide allows an improved distribution in
the polyester matrix.
This supplementary stage in the
technological dispersion process is
responsible for the mechanical properties
improvement and also the final product

quality represented by nanocomposite
material.

Acknowledgements

This work was supported by CNCSIS –
UEFISCSU, project number PNII – IDEI
519/2008 9/2008.

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