Designing of multiwalled carbon nanotubes reinforced polyurethane composites as electromagnetic interference shielding m
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ORIGINAL PAPER
Designing of multiwalled carbon nanotubes reinforced polyurethane composites as electromagnetic interference shielding materials T. K. Gupta & B. P. Singh & Satish Teotia & Varun Katyal & S. R. Dhakate & R. B. Mathur
Received: 28 December 2012 / Accepted: 6 May 2013 # Springer Science+Business Media Dordrecht 2013
Abstract Long length multiwalled carbon nanotubes (MWCNTs) were synthesized in-house by chemical vapor deposition and their reinforced polyurethane (PU) based composites were fabricated by solvent casting followed by compression moulding technique. Electromagnetic interference (EMI) shielding effectiveness of these composites was investigated in the frequency range of 8.2–12.4 GHz (Xband). The experimental results indicate that the EMI shielding effectiveness of the composites is achieved up to –41.6 dB at 10 wt.-% loading of MWCNT, indicating the usefulness of this material for EMI shielding in the Xband. The main reason for such a high improved shielding effectiveness has been attributed to the significant improvement in the electrical conductivity of the composites by 13 order of magnitude, i.e. from 10−14 for pure PU to 7.9 Scm−1 for MWCNT-PU composites. The mechanism of improvement in EMI shielding effectiveness is discussed by resolving their contribution in absorption and reflection loss. The experimental results were found in good agreement with theoretical correlations. Keywords Multiwalled carbon nanotubes . Polyurethane . Electromagnetic interference . Shielding effectiveness
Introduction The concept of creating both structural and functional nanocomposites with improved performance is currently T. K. Gupta : B. P. Singh : S. Teotia : V. Katyal : S. R. Dhakate : R. B. Mathur (*) Physics and Engineering of Carbon, Division of Material Physics and Engineering, CSIR-National Physical Laboratory, New Delhi 110012, India e-mail: [email protected]
under development in a wide variety of metallic, ceramic and polymeric matrices, although the emphasis to date has been on polymeric systems [1–3]. Addition of carbon nanotubes (CNT) into a polymer matrix can improve several properties including mechanical [4–10], thermo-mechanical [11], electrical [12–17], thermal [17–19], chemical [20] and optical properties [21]. Electromagnetic interference (EMI) shielding of radio frequency radiation is the more serious problem in the modern society because of more and more use of scientific electronic devices and communication instruments. Light weight EMI shielding materials are needed to protect the work place and environment from radiation coming from the computers and telecommunication equipments as well as for the protection of sensitive circuit[22]. Currently metal powders are used due to their high conductivity but the dispersed metal particles suffer disadvantages in terms of cost, weight, corrosion, poor processing, molding properties and could easily be oxidized in air borne systems. Further, metals mainly reflect the radiations and cannot be used in applications where absor
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