Morphological influence of graphitic carbon-based nanoparticles on the electromagnetic shielding performance of their polymer nanocomposites

Villacorta, Byron and Ogale, Amod (2013). Morphological influence of graphitic carbon-based nanoparticles on the electromagnetic shielding performance of their polymer nanocomposites. In: CARBON 2013, Copacabana, Rio de Janeiro, Brazil, (). 14-19 July 2013.

Author Villacorta, Byron
Ogale, Amod
Title of paper Morphological influence of graphitic carbon-based nanoparticles on the electromagnetic shielding performance of their polymer nanocomposites
Conference name CARBON 2013
Conference location Copacabana, Rio de Janeiro, Brazil
Conference dates 14-19 July 2013
Publication Year 2013
Sub-type Other
Language eng
Abstract/Summary The influence of the graphitic crystallinity of carbon nanoforms on the electrical transport properties of polymer nanocomposites has been previously reported [1-3]. However, the morphological and dimensional influence of different highly-graphitic carbon-based nanomodifiers on the electromagnetic shielding effectiveness (EM SE) of their nanocomposites has not been fully studied yet. In this study, therefore, nanocomposites made of two different heat-treated (HT, at graphitization temperatures of ~2500°C) carbon-based nanomodifiers: Pyrograf® III PR-19, Applied Science Inc. (diameter: 119±8 nm, length: 10±2 µm, L/D: ~85) and multi-walled carbon nanotubes, MWNT CheapTubes Inc. (diameter: 42±3 nm, length: 6±1 µm, L/D: ~ 145) dispersed in LLDPE matrix have been investigated for their EM SE. Raman spectroscopy was conducted for the particles to analyze the disordered (D) and graphitic (G) bands observed in carbon materials at 1315 cm-1 and 1580 cm-1, respectively. A Renishaw micro-Raman spectroscope equipped with a 785 nm wavelength diode laser was used. PR-19 HT CNF displayed an ID/IG Raman ratio of 0.961±0.044, whereas the MWNT HT had an ID/IG Raman ratio of 0.782±0.105 (n = 8 in all cases). In addition, the bulk electrical resistivity (BER) of the particles was measured using a Keithley 196 system digital multi-meter while compressing the particles at 50 MPa in an insulating fixture. Thus, the BER of the nanoparticles was 0.031±0.010 Ω•cm and 0.028±0.015 Ω•cm for PR-19 HT and MWNT HT respectively. Therefore, both heat-treated nanoparticles displayed similar graphitic crystallinity, which is confirmed by their alike electric transport, owing to their comparable BER. To compare the shielding performance of the composites, all composite types were processed at the same conditions in a Haake Rheomix 600 batch mixer (BM) at 190°C and 20 rpm for 2 min at a concentration of 10 vol%. The composites were processed by thermal compaction at 190°C into circular sheets about 2.5 mm thick and 133 mm diameter utilizing a Carver laboratory press for EM SE measurements (true replicates, n = 2). Thus, MWNT HT nanocomposites displayed a DC in-plane electrical conductivity of 33.5±5.6 S/m, whilst PR-19 HT CNF nanocomposites displayed a significantly lower of 20.4±3.3 S/m. This difference can be accounted for by the fact that, in spite of the similar intrinsic transport ability of both nanoparticles, the morphological differences must bring about a more conductive composite in the case of MWNT HT, because of its higher aspect ratio (L/D ~145) that increases the likelihood for electric transport through the electrical network formed by the particles within the matrix. Moreover, it is known that materials with higher conductivities should lead to higher EM SE [1, 4]. Thus, over the 30 MHz – 1.5 GHz frequency range, nanocomposites at 10 vol% containing MWNT HT and PR-19 HT possessed a shielding performance of about 24 dB and 22 dB, respectively, which is consistent with the conductivity levels reached for each nanoparticle type. Therefore, besides the graphitic crystallinity of the conductive nanoparticles, morphological and dimensional aspects will certainly influence the conductive electrical network of their polymer composites and ultimately their corresponding EM SE.
Q-Index Code EX
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Conference Paper
Collection: School of Chemical Engineering Publications
 
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Created: Sun, 17 May 2015, 21:05:04 EST by Byron Villacorta Hernandez on behalf of School of Chemical Engineering