Department of Plastic Engineering Injection molding of electrically conductive composites based on carbon nanotubes and carbon black

1
Department of Plastic EngineeringInjectio
n molding of electrically conductive composites
based on carbon nanotubes and carbon black

• Supervisor Dr. Fabian Rios
• Presented by Arik Noyman
• Lorin Bacal
  
  July 2009
  

2
Objectives

• Understanding of polymers electrical properties.
• Investigation of PC and PBT composites containing
  CB and CNT separately.
• Investigation of synergistic PC and PBT
  composites containing CB and CNT together.
• Creating composites combining CNT and CB in order
  to reduce the price and achieve better properties

3
Motivation

• Electronic components may damage from ESD during
  manufacturing, assembly, storage and shipping.
• There is a growing demand for conductive
  plastics.
• Plastic composites have advantageous
  price\weight\performance and easy processed.
• Composites containing both CB and CNT may present
  a synergistic effect in terms of price and
  properties

4
Introduction

• Most polymers are electrically insulating
  materials.
• Conductive Polymeric materials are usually
  polymer composites containing electrically
  conductive fillers.
• The type of filler used, its electrical
  conductivity and physical properties have a
  significant effect on the electrical conductivity
  of the composite.

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Conductive mechanism
CB
CNT
Electric conductivity occur when free electrons
move easily from atom to atom under an applied
electric field.
6
Applications

• Antistatic media (ESD elimination) .
• Battery and fuel cell electrodes.
• Corrosion-resistant conductive materials.

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Experimental - Materials

• PC Carbotex K-20 (Kotec)
• PBT Ramster PF-100 (polyram)
• CNT Nanocyl 7000 (Nanocyl)
• CB Vulcan XC72 (Cabot)

8
Experimental - Methodology

• Preparing the composites using a co-rotating
  twin screw extruder
• CNT composites 1.5 - 3.5 wt, with intervals of
  0.5 wt
• CB composites 6 - 16 wt, with intervals of 2
  wt
• Injection molding of the composites.
• Testing and characterization the injected samples
  

Stage 1 Percolation treshold
Electrical Resistivity
Tensile
Rheology
Impact
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Stage 2

• According to the percolation threshold (P.T.)
  found in stage 1,
• CB and CNT containing composites were prepared

CNT wt CB wt
0.25 P.T. 0.2 P.T.
0.25 P.T. 0.5 P.T.
0.25 P.T. 0.8 P.T.
0.5 P.T. 0.2 P.T.
0.5 P.T. 0.5 P.T.
0.5 P.T. 0.8 P.T.
0.75 P.T. 0.2 P.T.
0.75 P.T. 0.5 P.T.
0.75 P.T. 0.8 P.T.
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Results And Discussion stage 1

• Electrical Properties
• CNT composites

Percolation Threshold of CNT 3 wt for PBT

3.5 wt for PC
11
Results And Discussion Electrical properties

• CB composites

Percolation Threshold of CB 14 wt for both
materials

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Results And Discussion Mechanical Properties
Viscosity Impact strength Stress at break Elongation at break Youngs Modulus Property
PC\CB
PC\CNT
PBT\CB
PBT\CNT
composite
The table represent the conducting composites
compared to the neat matrix
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Stage 2 - composite containing CNT and CBTEM
image of a conductive composite containing CNT
and CB
CB
CNT
CARBON NANOTUBES A HIGH PERFORMANCE CONDUCTIVE
ADDITIVE 26
14
Results And Discussion stage 2

• Electrical Properties

15
Results And Discussion Economic Rentability
CNT cost 50 \Kg CB cost 5 \Kg
16
Results And Discussion PC composites properties
17
Results And Discussion PBT composites properties
18
Results And Discussion - Rheological behavior
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Results And Discussion - Rheological behavior
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Results And Discussion PC Properties Comparison
Total Elongation Impact (MD) Modulus Conductivity Price PC
5.2 7 6 9 5 10 PC 14CB
4.46 6 4 8 10 3 PC 3.5CNT
5.76 6 10 10 7 8 PC-1CNT-11CB
5.3 6 9 8 8 6 PC-2CNT-7CB
4.8 5 8 7 9 4 PC-2CNT-11CB
4.98 6 8 10 9 3 PC-3CNT-3CB
  6 7 4 10 9 Ranking
Best composite
Worst composite
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Results And Discussion PBT Properties
Comparison
Total Elongation Impact (MD) Modulus Conductivity Price PBT
4.92 4 6 10 5 10 PBT 14CB
5.2 10 10 6 7 4 PBT 3CNT
5.4 6 8 9 7 8 PBT-0.7CNT-11CB
5.68 7 9 9 8 7 PBT-1.3CNT-7CB
5.6 5 8 10 10 6 PBT-1.3CNT-11CB
4.88 8 10 8 4 6 PBT-2CNT-3CB
  6 7 4 10 9 Ranking
Best composite
Worst composite
22
Conclusions

• Electrical Resistivity
• Addition of CNT and CB separately into PC and PBT
  creates conductive composites.
• PC demonstrated higher percolation threshold
  than PBT.
• Addition of both CNT's and CB into the same
  polymeric matrix increases the electrical
  conductivity, positive synergy was achieved.

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Conclusions - Mechanical Properties

• The filler leads to higher stiffness of the
  composites an increase in the Young's modulus
  and a decrease in elongation.
• CNT's reinforce the composites more efficiently
  than CB.
• Positive synergy of the mixed additive composites
  can be easily achieved using standard processing
  parameters.
•  

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Conclusions - Rheological Characterization

• CNT has greater effect on the viscosity than CB.
• The electrically conductive composites had showed
  a shear-thinning
• behavior.
• PC mixed-additive composites behavior resembles
  the PC\CNT behavior.
• PBT mixed-additive composites viscosity had
  decreased compared to the PBT\CNT

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Conclusions - General

• Reducing the CNT content in CNT-based composites
  and incorporating CB into the same matrix
  decreases the electrical resistivity by a
  synergistic effect along with an improvement of
  mechanical properties compared to the single
  additive composites.
• The composite that demonstrated the best
  properties combination were
• PBT-1.3CNT-7CB, PBT-1.3CNT-11CB
• PC-1CNT-11CB and PC-2CNT-7CB.

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Further work

• Composites that are recommended to perform DOE on
  are
• PBT-0.7CNT-11CB, PBT-1.3CNT-7CB, PBT-1.3CNT-11CB
• PC-1CNT-11CB and PC-2CNT-7CB
• A dispersion agent should be used in CB
  compounding.
• Surface treatment for the CNT.
• A TEM investigation should be done in order to
  understand the morphological structure of the
  composites.
• Finding a compitabilizer that improves the
  deformation ability is highly desirable.

27
Acknowledgments

• Dr. Fabian Rios
• Rachel Lipman
• Shura Muchlove
• Yossi Hazut
• Irena Belinski
• Moshe Rubino
• Roni Efrati

28
Thank You
29
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