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Materials 2016, 9(11), 923; doi:10.3390/ma9110923

Metamaterial Behavior of Polymer Nanocomposites Based on Polypropylene/Multi-Walled Carbon Nanotubes Fabricated by Means of Ultrasound-Assisted Extrusion

1
Innovación y Desarrollo en Materiales Avanzados A. C., Grupo POLYnnova, Carr. San Luis Potosí-Guadalajara 1510, Nivel 3, Local 12, Lomas del Tecnológico, San Luis Potosí, S.L.P. C.P. 78211, Mexico
2
Centro de Investigación en Química Aplicada, Blvd. Ing. Enrique Reyna H. 140, Col. San José de los Cerritos, Saltillo, Coahuila C.P. 25294, Mexico
*
Author to whom correspondence should be addressed.
Academic Editor: Marco Morreale
Received: 13 September 2016 / Revised: 26 October 2016 / Accepted: 7 November 2016 / Published: 14 November 2016
(This article belongs to the Section Advanced Composites)
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Abstract

Metamaterial behavior of polymer nanocomposites (NCs) based on isotactic polypropylene (iPP) and multi-walled carbon nanotubes (MWCNTs) was investigated based on the observation of a negative dielectric constant (ε′). It is demonstrated that as the dielectric constant switches from negative to positive, the plasma frequency (ωp) depends strongly on the ultrasound-assisted fabrication method, as well as on the melt flow index of the iPP. NCs were fabricated using ultrasound-assisted extrusion methods with 10 wt % loadings of MWCNTs in iPPs with different melt flow indices (MFI). AC electrical conductivity (σ(AC)) as a function of frequency was determined to complement the electrical classification of the NCs, which were previously designated as insulating (I), static-dissipative (SD), and conductive (C) materials. It was found that the SD and C materials can also be classified as metamaterials (M). This type of behavior emerges from the negative dielectric constant observed at low frequencies although, at certain frequencies, the dielectric constant becomes positive. Our method of fabrication allows for the preparation of metamaterials with tunable ωp. iPP pure samples show only positive dielectric constants. Electrical conductivity increases in all cases with the addition of MWCNTs with the largest increases observed for samples with the highest MFI. A relationship between MFI and the fabrication method, with respect to electrical properties, is reported. View Full-Text
Keywords: polypropylene; carbon nanotubes; melt flow index; extrusion; ultrasound; AC electrical properties; negative dielectric constant; metamaterials polypropylene; carbon nanotubes; melt flow index; extrusion; ultrasound; AC electrical properties; negative dielectric constant; metamaterials
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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MDPI and ACS Style

Pérez-Medina, J.C.; Waldo-Mendoza, M.A.; Cruz-Delgado, V.J.; Quiñones-Jurado, Z.V.; González-Morones, P.; Ziolo, R.F.; Martínez-Colunga, J.G.; Soriano-Corral, F.; Avila-Orta, C.A. Metamaterial Behavior of Polymer Nanocomposites Based on Polypropylene/Multi-Walled Carbon Nanotubes Fabricated by Means of Ultrasound-Assisted Extrusion. Materials 2016, 9, 923.

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