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…

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 ~ 100-1000 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 ~ 12 - 45

Problems with Conventional Capacitors 1 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 http://us.sanyo.com 2 1- http://ashleyelec58502.wordpress.com 2- http://us.sanyo.com

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

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

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 www.techfoam.com

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

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

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

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

Foam Morphology (SEM) Cell size ~ 5 – 150 mm Relative density = 0.55 - 0.65 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

Foam Morphology (TEM)

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

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

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.

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

Discussion

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

Question? Thank you. www.ucalgary.ca/medal

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