Dispersion of Carbon Nanotubes Into

Report
Nur Hidayah Binti Azmi
Hafizul Bin Tukimin
Mohd Syafiq Bin Mansor
T. Basiron Bin T. Yusof
Mohd Ruba’I Amir Bin Salleh
Che Muhd Firdaus Bin Che Mat
Mohammad Ikmal Bin Mohamed
B050910244
B050910075
B050810293
B050910300
B050910143
B050910271
B050810223
 Dispersion
in chemistry means; the mixture in
which fine particles of one substance are
scattered throughout another substance.
 There are 2 major type of dispersion:
 Intragranular

In the grain.
 Intergranular

At the grain boundaries.
 Melt
processing is a common alternative that
is particular useful for dealing with
thermoplastics polymers.
 Carbon nanotubes can be mixed into the
polymer melt by shear mixing.
 Melt blending is sometimes less effective at
dispersing nanotubes in polymers because
nanotubes can effect melt properties such as
viscosity.
 The shear force of the melt mixing method
was favorable for the homogeneous
dispersion of MWNTs.
The
percolation
composition as detected by
electrical resistivity
measurements.
Stress-strain behavior of
the composites.
 Commercially
available masterbatches of
nanotube /polymer composites are used as the
starting material which are diluted by the pure
polymer in a subsequent melt mixing process
(masterbatch dilution method).
 Nanotubes are directly incorporated into the
polymer matrix.
Electrical conductivity
 Improvement of mechanical properties, especially
strength
 Enhancement of thermal stability
 Enhancement of thermal conductivity
 Improvement of fire retardancy
 Enhancement of oxidation stability


Effects at low CNT contents because of the very high
aspect ratio
•
•
1.
2.
3.
A master batch of 15 wt% MWNT1 in
polycarbonate was diluted with different kinds of
polycarbonate.
The polycarbonates used for this studies were:
PC Iupilon E2000 (PC1, powder, Mitsubishi
Engineering Plastic, Japan) with zero shear
viscosity at 260 °C of 6800 Pa-s.
PC Lexan 121 ( PC2, granules, GE Europe with
zero shear viscosity at 260°C of 3500 Pa-s)
PC used for masterbatch production ( PC3,
powder, supplied by Hyperion Cat with zero
shear viscosity at 260 °C of 1000 Pa-s.





Melt compounding was carried out between 240 and 280
°C using a Haake twin screw extruder, a small scale
DACA Micro Computer , or a Brabender PL-19 single
screw extruder.
The materials were dried at 120 °C in vacuum for at least
4h and fed as granular premixture.
Direct incorperation of MWNT and SWNT was performed
using the small scale (4.5cm3 material) DACA Micro
Computer.
After drying of polymer and nanotubes (100°C, 2h
vacuum) the materials were premixed and fed to the
running compounder.
For direct incorporation of the MWNT2 (purity >95%.
Diameters 20-50nm, length up to more than 100 µm,
produce at Leibniz- Institute for Solid State and Materials
Research Dresden by thermal cathalytic CVD ) were
incorporated into PC2 at 260 °C, 50 rpm, and 5 min.
SWNT (unpurified arc-discharge material, bundled,
single tube diameters of 1.0-1.3nm, prepared at the
Max- Planck- Institute for Solid State Research
Stuttgart) were incorporation into PC1 powder at
280°C, 50rpm, and 15 min.
 Electrical volume resistivity was measure on
compression molded sheets (diameter > 60nm,
thickness 0.35mm).
 A Keithley electrometer Model 6517 equipped with
an 8009 Resistivity Test Fixture was used to measure
high resistivity sample.
 Lower resistivity composites were measured by four
point test fixture combine with a Keithley
electrometer Model 2000 using strip (20mm x 3mm)
cut from the sheets.




In addition, dielectric measurement were performed at
room temperature in a frequency range from 10-3 to 107
Hz using a frequency response analysis system consisting
of Solartron of
SI1260 Impedance/Gain Phase Analyzer and Novocontrol
broadband dielectric converter with the BDC active
sample cell.
Discs (diameter of 20 mm) were cut from the sheets and
gold layers were sputtered onto both sides as electrodes.
Scanning electron microscopy (SEM) was performed
using a LEO VP 435 scanning electron microscope (Leo
Elektronenmikroskopie, Germany) on raw materials or
fractured samples. Mechanical testing of miniature
dogbones (length 20 mm, parallel length 6 mm, gauge
width 2 mm) punched from the pressed sheets was
performed similar to ISO 527-2 on a Zwick Z010 tensile
tester at an extension rate of 5 mm/min. The values are
mean values of 10 tests.
Result
&Discussion

→ Using the masterbatch dilution method, the PC
based masterbatch with 15 wt% MWNT consists of
highly interconnected tubes in the PC3 matrix which
show a good wetting of the tubes with polymer.

→ If the dilution is properly performed, the MWNT
should be homogeneously distributed and dispersed
in the matrix.

→ Resistivity vs. composition dependencies can be
used to
detect the percolation composition unequivocally. In
addition, the resistivity values can give information
about the state of dispersion obtained at a given
composition.

 Depending
on the PC and mixing equipment,
percolation was reached between 0.5 and1.5 wt%
MWNT1 content.





In all the cases, composites with contents starting at 1.5
wt% MWNT1 can be regarded as electrically conductive
4
(volume resistivity <10 Ohm-cm).
For the example of masterbatch dilution with PC3 using
the DACA Micro Compounder the influence of
processing conditions at compositions near the
percolation was investigated more in detail using
dielectric spectroscopy.
Figure 2 shows the AC conductivity for composites
containing 1.0 and 1.5 wt% MWNT1.
It is interesting to note that in the case of 1.0 wt%
variations in the processing conditions (increasing mixing
time) can transform a nonpercolated structure in a
percolated one.
The relatively low percolation thresholds indicates a quite
good distribution and dispersion within the PC matrices
as it was shown by TEM.
 Using
the direct incorporation method, next
to a good distribution and dispersion of the
tubes also a wetting of the nanotube surface
with polymer has to be achieved which
depends :-
a) CNT surface characteristics and amount.
b) The interfacial tension between nanotube
surface and polymer melt .
c)
The polymer melt viscosity.
 For
the second case, the MWNT that
used are MWNT2 (Fig. 3) are relatively
long, less tangled and quite straight.
 It is assumed that some of the very long
tubes break during melt mixing with
high viscous polymers.
 The cryo fracture shown in Fig. 4
illustrates a homogeneous distribution
and dispersion without agglomeration
of the nanotubes.
 In this system, percolation started at 3
wt% MWNT2 addition.
The
incorporation of nanotubes
significantly changes the stressstrain behavior of the composites
as it is shown in Fig. 4.
PC2 exhibits a pronounced
yielding behavior followed by
cold drawing and shows
elongation at break of about 30%.
 After
adding MWNT2, next to an increase
in Young’s modulus (9% at 1wt% and 16%
at 5wt% MWNT2) the elongation at break
is reduced dramatically starting at 1.5 wt%
MWNT2 since the nanotubes start to form a
network.
 Starting at 2 wt% MWNT2, the pronounced
yielding and cold drawing behavior is no
longer visible and the break occurs before
reaching the elongation (and stress) typical
for the yield point of the pure PC.
Graph(Figure 4) shows that the increasing of young
modulus with SWNT addition (46% at 7.5 wt%
SWNT) is higher than PC2/MWNT2 composites.
 The pronounced cold drawing behavior after
yielding is observable up to 3 wt% SWNT.
 Stress at yield is increased by about 7 MPa as well as
the stress level beyond the yield point.
 At higher SWNT contents the break occurs just after
the yield point leading to significantly decreased
elongations at break.
 This behavior can be understood by the percolated
network of the SWNT which hinders the
polycarbonate in its typical deformation behavior
especially in developing a cold drawing process

Melt
mixing by using
masterbatch technique can be
apply on:
 Small and medium sized
enterprises
• Reason:
― applicable and easy accessible
 1.5wt%
MWNT by using masterbatch
technique and already reach 0.5wt% MWNT
by using Brabender PL-19.
 By using melt mixing, it can leads to good
dispersion of CNT in Polycarbonate.
 Percolation 2-3wt% CNT
• Stress-strain behavior
― Increase modulus and stress
― Decrease on elongation cause percolation
concentration
Thank
You….
Melt mixing consists of melting the polymers and
mixing with nanotubes in high shear process. High
shear forces are responsible for producing well –
dispersed nanotubes on both the micro and nanoscale
dispersion resulting from melt mixing is interior to that
resulting from solution method. For thermoplastic
polimers. Melt mixing is the most desirable way to
combine nanotubes and polymers for most application.
It is because MWNTs can be dispersed adequately in a
twin screw extruder while SWNTs. A twin screw
extruder has generally been used to mix polymers and
nanotubess in order to generate the high forces for
maximum dispersion.
There are currently three processes for producing carbon
nanotubes: arc discharge, laser ablation and catalytic
decomposition. The arc discharge method was what helped
carbon nanotubes (MWNTs) to attract widespread attention in
1991. 1993 saw the discovery of single-wall carbon nanotubes,
which can also be produced by the light arc method if catalysts
are added. In 1996, a laser process was introduced for the
production of single-wall carbon nanotubes. With this method,
graphite is evaporated with the aid of a laser. The third
possibility for producing CNTs involves the catalytic
decomposition of hydrocarbons. This process offers the
advantage that largely parallel carbon tubes can be produced.
All three processes are now so well developed that
homogenous CNTs can be produced to order.
The first CNT-based products are already on the market in the leisure sector.
Sports equipment manufacturer Völkl, for example, has produced a tennis
racket in which small quantities of CNTs are added to the plastic used for the
frame and handle. Nanotubes can also be found in bicycle handlebars from
Easton and golf clubs from Aldila. The Finnish ice hockey team uses sticks
containing carbon nanotubes from Bayer MaterialScience. Other applications
in the sports sector include bicycle helmets, skis, surfboards, baseball bats
and sports shoes made of plastics containing CNTs. There also a number of
CNT-based products successfully being used in industry. One example is a
plastics drum with an antistatic outer coating based on Baytubes and
manufactured by the firm Schütz GmbH. It is used as a high-grade transport
packaging to ensure that flammable goods such as solvents and oils cannot
ignite as a result of electrostatic discharge. These properties also make
Baytubes interesting for fuel lines. Another example is a conductive plastic
incorporating carbon nanotubes from Bayer MaterialScience that has been
produced by the Ensinger company since mid-2007 and is used to
manufacture parts for the outer skin of Formula 1 cars, aircraft and other
vehicles.
 Intermolecular
Attractions between one molecule and a
neighbouring molecule.
 Intramolecular
The forces of attraction which hold an
individual molecule together (for example,
the covalent bonds)
 Van
Der Waals
Molecules can attract each other at
moderate distances and repel each other at
close range. Van der Waals forces are much
weaker than chemical bonds, and random
thermal motion around room temperature
can usually overcome or disrupt them.
What are the factors that
influence percolation of
polycarbonate based material?
 The
result obtained for polycarbonate based
material show that the percolation only
slightly depends on



the PC used for dilution
the mixing equipment
and the processing conditions.

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