Electromagnetic Interference Shielding Properties of Injection Molded and Compression Molded Multi-walled Carbon Nanotube/Polystyrene Composites M. Arjmand1, T. Apperley2, M. Okoniewski2, U. Sundararaj1* 1Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Canada 2Department of Electrical and Computer Engineering, University of Calgary, Calgary, Canada PPS – 28 Dec 11-15, thailand

electromagnetic interference (emi) hazards 2 1 Thermographic image of the head: (a) with no exposure to harmful cell phone radiation; (b) after a 15-min phone-call. Yellow and red areas indicate thermal (heating) effects. www.hardwareinsight.com www.biotele.com

conductive filler / polymer composites (CPCs) as EMI shields CPCs have many advantages over metals in terms of: Processability Light Weight Resistance to Corrosion Low Cost

EMI SHIELDING MECHANISMS Incident Power PI EMI Shielding Mechanisms: 1- Reflection 2- Absorption 3- Multiple-Reflections PI-R Reflected Power PR Transmitted Power PT SE = 10 · log (PI/PT) Expressed in dB

Typical curves of electrical conductivity and EMI SE versus filler concentration for CPCs 1Arjmand M, Apperley T, Okoniewski M, and Sundararaj U. Carbon 2012; 50: 5126-34.

incentives to investigate effects of carbon nanotube alignment on EMI shielding mechanisms Unavoidable flow-induced alignment of carbon nanotubes (CNTs) in injection molding process The importance of the knowledge of EMI shielding mechanisms in the design of CPCs as EMI shields

Experimental (Cont’d) Injection Molding BOY 12A Polystyrene Masterbatch 20 wt% (MB2020-00) Blending with Twin-Screw Extruder “Coperion ZSK” Compression Molding Pure Polystyrene (Styron® 610)

Experimental Composite Molding Compression Molding: Carver Plate Press: 210 oC, 38 MPa, 10 min Injection Molding EXP # Mold Temp. (°C) Melt Temp. (°C) Injection Press. (bar) Injection Vel. (mm.s-1) 1 60 215 100 240 2 3 24

Raman spectroscopy ratios parallel/perpendicular ┴/DװD ┴/GװG Compression Molding 1.01 EXP #1 1.66 1.51 EXP #2 1.53 1.44 EXP #3 1.35 1.27 The order of the Raman intensity ratios, and consequently MWCNT alignment, from the highest to the lowest is EXP #1 > EXP #2 > EXP #3 > compression molded samples.

effects of mwcnt alignment on dc conductivity and emi se The order of electrical conductivity and EMI SE from the highest to the lowest is compression molded samples > EXP #3 > EXP #2 > EXP #1. EMI shielding does not require filler connectivity; however, it increases with filler connectivity.

EFFECTS OF MWCNT ALIGNMENT ON REAL PERMITTIVITY AND IMAGINARY PERMITTIVITY The order of real permittivity and imaginary permittivity from the highest to the lowest is compression molded samples > EXP #3 > EXP #2 > EXP #1.

conceptualization of the effects of alignment on real and imaginary permittivities + + - + + + + - + +

hierarchy of random distribution of MWCNTs and higher EMI SE Greater Probability of MWCNT Contacts Greater Electrons’ Mean Free Path Higher Imaginary Permittivity and Ohmic loss Higher EMI SE Higher Applied Electric Field Between MWCNTs Higher Real Permittivity and Polarization loss

Conclusions MWCNT alignment has an adverse effect on electrical properties. EMI shielding does not require filler connectivity; however, it increases with filler connectivity. Measuring electrical conductivity and real and imaginary permittivities can give an idea about EMI SE. In order to achieve conductive composites with high EMI shielding performance, designing the mold and processing conditions in injection molding process should be performed as to achieve random distribution of conductive filler.

Acknowledgements Natural Sciences and Engineering Research Council of Canada (NSERC). Dr. Tieqi Li and Ms. Jeri-Lynn Bellamy in Nova Chemicals®, Calgary, AB, Canada for the polymer extrusion/blending Mr. Mehdi Mahmoodi and Dr. Simon Park, Department of Mechanical and Manufacturing Engineering, University of Calgary for assistance with the mold design and manufacturing Dr. Samaneh Abbasi of Ecole Polytechnique (Montreal, Canada) for assistance with Raman spectroscopy Americas Styrenics LLC, for Providing Pure Polystyrene.

THANKS FOR YOUR ATTENTION! u.sundararaj@ucalgary.ca marjmand@ucalgary.ca

Effects of MWCNT alignment on shieldings by reflection and absorption

Morphological Analysis Injection molding (EXP #1) Compression Molding

Injection Molding vs Compression Molding: Length Distribution

Experimental Injection Molding Our previous study showed that the melt temperature had the greatest impact on MWCNT alignment followed by the injection velocity, while the impacts of mold temperature and injection/holding pressure were insignificant.1 Levels (set points) of the processing parameters used in the injection molding experiments (EXPs). The processing parameters are mold temperature (C1), melt temperature (C2), injection/holding pressure (C3) and injection velocity (C4). EXP # C1 (°C) C2 (°C) C3 (bar) C4 (mm.s-1) 1 60 215 100 240 2 3 24 Parameter Value (mm) a 22.86 b 10.16 c, d 1 e 2 f 10 1 Mahmoodi M, Arjmand M, Sundararaj U, Park S. Carbon 2012; 50(4):1455-64.

Raman spectroscopy ratios parallel/perpendicular Two significant characteristics in the Raman spectra of the MWCNT/polymer composites are the D band (disorder band), and the G band (graphite band). The Dװ/D ┴and Gװ/G ┴ parallel/perpendicular to the flow direction were used to determine the degree of MWCNT alignment. Raman spectroscopy ratios parallel/perpendicular ┴/DװD ┴/GװG Compression Molding 1.01 EXP #1 1.66 1.51 EXP #2 1.53 1.44 EXP #3 1.35 1.27 The order of the Raman intensity ratios, and consequently MWCNT alignment, from the highest to the lowest is EXP #1 > EXP #2 > EXP #3 > compression molded samples.