Preparation and Characterization of Carbon Nanotube Reinforced Polyetherimide
Composites by Solution Mixing Method
Santiago Caceres
Cal Poly, San Luis Obispo - WSU - REU Program
Dr. Sandeep Kumar (Project Supervisor), Dr. Katie Zhong (Faculty Advisor)
School of Mechanical and Materials Engineering Washington State University, Pullman, WA 99164
This work was supported by the National Science Foundation’s REU program under grant number DMR-0755055, NSF grant number 0758251, and the Boeing grant
Method:
The goal for processing was to effectively transfer
the potential mechanical and electrical properties of
the MWNTs to the PEI matrix. The two main
challenges involved with the fabrication of novel
nanocomposites are:
! Dispersion
! Interfacial Bonding
Procedures:
PEI
Powder
Dispersion of the multi-wall carbon nanotubes in the nano-composites was characterized
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by field scanning electron microscope( FESEM). It was observed that functionalized
MWNTs were homogeneously dispersed and embedded within the polyetherimide
matrix. Figure 2 (a) shows good interfacial interaction, while Figure 2 (b) shows $"""
dispersion of MWNTs within the PEI matrix.
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Polyetherimide (PEI), is a high performance
thermoplastic known for its high heat resistance
and good mechanical properties. By adding nanoscaled fillers into the PEI matrix, we may be able
to obtain unique properties in the newly formed
composite. If the mechanical and electrical
properties can be improved by the introduction of
an effectively dispersed nano-filler through the
appropriate method, this
high performance polymer
nanocomposite may be
considered as a multifunctional interior
material in the next
generation of safe, fuel
efficient light weight
aircrafts, and other low
density high performance
applications. The dispersion
behavior, mechanical,
thermal and electrical
Multi walled carbon nanotube
properties of functionalized
multi walled carbon nanotube (MWNT)-PEI
nanocomposites were investigated.
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Temperature,
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Figure 6. DMA results for various
MWNT loading and scheme of
Systematic mechanism of increase in storage modulus with temperature.
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Figure 2. FESEM images of PEI/MWNT composite showing good adhesion left (0.5 wt% MWNT) and dispersion right (1.0
wt%, (MWNT)
Interfacial Interactions:
Thermogravimetric Analysis (TGA):
Temperature, !
Figure 4. TGA Graph of Pure PEI and nanocomposites
Electrical Analysis:
Figure 3. Mechanism of interfacial
interaction of COOH-MWNTs with PEI
TGA graph in figure
4 show the thermal
stability of PEI/
MWNT composites
increase as MWNT
loading increases.
This suggests that the
MWNTs act as a
mass-transport
protective barrier that
slows down
degradation of the
polymer.
Pure PEI
PEI MWNTs ( 0.5 wt%)
PEI MWNTs ( 1.0 wt%)
PEI MWNTs ( 7.0 wt%)
DMA showed high increase in storage modulus (E')
with the incorporation of MWNTs as compared to
pure PEI. The increase was due to decreased mobility
of the polymer chain due to the formation of plenty
of cross linking sites between polymer and MWNTs.
Electrical properties of the PEI/MWNT
composites were investigated. The results show
that the percolation behavior lies between 0.3 and
0.5 wt% loading of MWNTs in the PEI matrix.
the materials electrical resistivity dramatically
drops from about 17 ohm*cm to 5.5 ohm*cm.
By adding a COOH group to the MWNTs, interfacial interactions
between the two materials can be much stronger and therefore transfer
the nano fillers properties much more efficiently to the matrix. Figure
3 shows the mechanism of this interaction.
PEI/MWNT In DCM Mixture
>Ultrasonication (45min)
> Sample Left overnight for DCM evaporation
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PEI
MWNTs
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PEI
MWNTs
( 1.0
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PEI
MWNTs
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PEI
MWNTs
( 7.0
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Weight Loss %
PEI/MWNT In DCM Mixture
>Stir (1hr)
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MWNT
MWNT In DCM
>Sonication (1hr)
>Ultrasonication (15 min)
PEI In DCM
>Stir (1hr)
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! PEI was dissolved in
methylene chloride
(DCM) and stirred for at
least 1 hour.
! Functionalized
MWNTs were dissolved
in DCM, sonicated for 1
hour, then immediately
placed into horn type
Ultrasonication for 15
minutes.
! The MWNT solution
was then mixed with the
PEI solution and stirred
for 1 hour.
!PEI/MWNT solution
Ultrasonicated 45
minutes.
! Solution cast into a
glass dish, covered, and
left to dry overnight
! Samples removed
from glass dish and dried
in a oven for at least 4
hours at 60 !.
Dynamic Mechanical Analysis (DMA):
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SEM Analysis:
Introduction:
PEI Matrix
Figure 7. Graph showing Resistivity Vs. wt% loading for MWNT-PEI
composites. Percolation for electrical conductivity is observed
between 0.3 - 0.5 wt% loading.
Conclusions:
Dispersion behavior, mechanical, thermal and
electrical properties of functionalized MWNT/
PEI nanocomposites were investigated:
! Alternating sonification and ultrasonification
PEI/MWNT Composite Film
> Film Dried in oven 4 hrs at 60 !
Morphology (FESEM)
Electrical Properties
Thermal Properties
Film Sample
Viscoelastic Properties
Figure 1. Process procedure outline
Figure 5. Mechanism of how
MWNTs impede the removal of
bulk PEI from going to the vapor
phase.
MWNT
Interphase
Figure 5. Scheme showing resone for increase in Tg of nanocomposites
is a successful method of dispersing MWNTs in a
PEI matrix
! The addition of functionalized MWNTs
significantly increases PEI’s thermal stability
! PEI’s storage modulus is increased due to
support provided by the MWNTs reinforcement.
! Electrical Percolation is observed between 0.3
and 0.5 wt% loading