Eur. Phys. J. E (2021) 44: 73
https://doi.org/10.1140/epje/s10189-021-00079-w

Regular Article - Soft Matter

Dielectric spectroscopy of melt-extruded polypropylene and as-grown carbon nanofiber composites

¹ 2C2T – Centre for Textile Science and Technology, University of Minho, Campus de Azurém, 4800-058, Guimarães, Portugal
² Laboratory of Material Physics and Subatomic, Faculty of Sciences, Ibn Tofail University, BP 242, 14000, Kenitra, Morocco
³ MEMS – UMinho, University of Minho, Campus of Azurém, 4800-058, Guimarães, Portugal
⁴ INL – International Iberian Nanotechnology Laboratory, Av. Mestre. Jose Veiga, Braga, Portugal
⁵ CFUM – Center of Physics of the University of Minho, Campus de Gualtar, 4710-057, Braga, Portugal
⁶ IFIMUP – Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre 687, 4169-007, Porto, Portugal

^a ajpaleovieito@2c2t.uminho.pt
^h me.achour@uit.ac.ma

Received: 26 February 2021
Accepted: 12 May 2021
Published online: 28 May 2021

Abstract

In this work, different weight contents of as-grown carbon nanofibers (CNFs), produced by chemical vapor deposition, were melt-extruded with polypropylene (PP) and their morphologic, structure and dielectric properties examined. The morphologic analysis reveals that the CNFs are randomly distributed in the form of agglomerates within the PP matrix, whereas the structural results depicted by Raman analysis suggest that the degree of disorder of the as-received CNFs was not affected in the PP/CNF composites. The AC conductivity of PP/CNF composites at room temperature evidenced an insulator–conductor transition in the vicinity of 2 wt.%, corresponding to a remarkable rise of the dielectric permittivity up to 12 at 400 Hz, with respect to the neat PP ( 2.5). Accordingly, the AC conductivity and dielectric permittivity of PP/CNF 2 wt.% composites were evaluated by using power laws and discussed in the framework of the intercluster polarization model. Finally, the complex impedance and Nyquist plots of the PP/CNF composites are analyzed by using equivalent circuit models, consisting of a constant phase element (CPE). The analysis gathered in here aims at contributing to the better understanding of the enhanced dielectric properties of low-conducting polymer composites filled with carbon nanofibers.