1. M. Mahmoodi1, M. Arjmand2, U. Sundararaj2 and S. S. Park1
BROADBAND DIELECTRIC SPECTROSCOPY OF MWCNT FILLED POLYSTYRENE FOAMED NANOCOMPOSITES
M. Mahmoodi1, M. Arjmand2, U. Sundararaj2 and S. S. Park1
1Micro Engineering, Dynamics Automation Lab (MEDAL)
Department of Mechanical and Manufacturing Eng., University of Calgary, Calgary, Alberta, Canada
2Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, AB
Trying to use injection molding to align cnts… through shear flow…
And investigate what kind of effects you may have when you have aligned cnts…

2. CNT Based Nano Composites
Lighter and stronger materials
Lighter automobiles with improved safety (exterior fenders and etc.)
Young’s modulus of 1 Tpa
Thermal conductivity ~ 3000 W/mK
Aspect ratio ~
Conductive polymers
Antistatic dissipation
EMI shielding properties
Electrostatic painting
Resistance to corrosion
Pure PC
5% MWCNT- PC
E: 70 Gpa for Aluminium, 200 Gpa for steel, 700 Gpa for C-fiber
Thermal cond. of copper ~ 400, Thermal cond. of steel ~

3. Problems with Conventional Capacitors1
Parallel plate capacitors
Dimension (micro components)
Linear Capacitance
Ceramic filled polymer Capacitors
High ceramic loading (>50 vol %)
Poor adhesion
Challenges in processing
Al / polymer capacitor 2 1- 2-

4. Basic Prerequisites for Embedded Capacitors
High dielectric constant
Low imaginary permittivity (current leakage)
Process compatibility with PCB
Embedded capacitor
Imanaka et al. ECERS, 2007

5. Challenges in Manipulating CNT / Polymer Capacitors
Quick Percolation Transition
km = 1.9
fc=0.005

6. Chemical Foaming of Nanocomposite
Thermal decomposition of Azodicarbonamide
1. Diffusion
2. Nucleation
3. Bubble Growth
Reciprocating screw
Optional
Shutoff
Nozzle
Mold
Diffusion
(single phase)
Bubble Growth
Nucleation

7. Objectives
Broadening the insulative – conductive region in CNT-filled nanocomposites through chemical foaming
investigating the dielectric properties of foamed nanocomposites

8. Injection Mold Micro machining using a 3-axis kern CNC machine
Spindle speed: 60 krpm

9. 20% MWCNT/PS masterbatch
Experiments
20% MWCNT/PS masterbatch
Foam Injection Molding
MWCNT/PS
with deferent
concentrations
Melt Mixing
Plain PS (MFI: 11 g/10 min)
Compression Molding

10. Exp. Setup: Inj. Molding and Elec. Testing
Conductivity measurement machine
Conductivity measurement machine (loresta-low resistivity)

11. Foam Morphology (SEM) Cell size ~ 5 – 150 mm
Relative density =
Wt.% of CNTs
Vol.% of CNTs
before foaming
Relative density of
the foam (kg/m3)
Vol.% of
CNTs
after foaming
0.10
0.06
0.60
0.036
0.30
0.18
0.55
0.099
0.50
0.64
0.192
1.00
0.61
0.65
0.396
2.00
1.22
0.63
0.768
3.50
2.18
1.330
5.00
3.16
2.022
10.00
6.67
4.335
MWCNT

12. Foam Morphology (TEM)

13. DC Electrical Resistivity
Thermodynamic instability induces CNT agglomeration
Deterioration in connectivity between CNTs

14. AC Electrical Resistivity
Compression Molded PS / CNT
Ascending trend with increase in frequency below percolation threshold
Independent from frequency after a certain CNT concentration
Foamed PS / CNT

15. 2 wt.% Compression Molded
Real Permittivity
Compression Molded PS / CNT
Foamed PS / CNT
At 1000 Hz
Pure PS
2 wt.% Foamed
2 wt.% Compression Molded
Real Per.
The variation of different types of polarization with time under a step-function electric field F.

16. Dissipation Factor Dissipation Factor:
Compression Molded PS / CNT
Dissipation Factor:
Ratio of the loss factor to the real permittivity
A measure of he electric energy loss to the electric energy stored in a periodic electric field
Foamed PS / CNT

17. Discussion

18. Conclusions
Mold design and process conditions strongly affect the alignment and electrical conductivity
Melt temperature and injection velocity showed more effect on the CNT alignment
Interaction of melt temperature, injection velocity and injection pressure influence the CNT alignment.
Non-ohmic behaviour for all the molded CNT / PS composites

19. Question?
Thank you.

20. Outline Introduction Objectives Experimental Setup Alignment of MWCNTs
9/12/2018
Introduction
Carbon Nanotube (CNT) Nanocomposites
CNTs as capacitors
Objectives
Experimental Setup
Alignment of MWCNTs
Electrical properties
Electrical conductivity
I-V characteristics
Conclusion