Electrical properties of polypropylene-based composites melt-processed with as-grown carbon nanofibers

Electrical conductivity, dielectric permittivity, electrical modulus, and electrical impedance of polypropylene (PP) composites melt-processed with different contents of as-grown carbon nanofibers (CNFs) are studied. As expected, the electrical conductivity of PP/CNF composites increased as the incorporation of CNFs is raised in the polymer, yielding a maximum of ∼ 6 ×10−6 S m−1 for PP/CNF 3 wt. % composites. That enhancement relates to a gradual improvement of the dielectric permittivity as the incorporation of CNFs rises into the PP up to a maximum of ∼ 13 for PP/CNF 3 wt. % composites at 1MHz, which is attributed to the rise of the interface polarization effect. Moreover, the Cole-Cole model is used through the electrical modulus to analyze the effect of CNF contents on the dielectric relaxation of PP/CNF composites from which is deduced that the incorporation of CNFs increases their heterogeneity and relaxation times. The analysis gathered here aims at contributing to the understanding of the electric features of polymer composites filled with a type of CNFs, which are not subjected to any thermal post-processing method after their synthesis by chemical vapor deposition (CVD).This research was funded by the project UID/CTM/00264/2021 of 2C2T under the COMPETE and FCT/MCTES (PIDDAC) co-financed by FEDER through the PT2020 program

Electrical properties of melt-mixed polypropylene and as-grown carbon nanofiber composites: analysis of their interphase via the AC conductivity modeling

The morphology, crystallinity, and electrical conductivity (σ′ and σ″) as a function of frequency of polypropylene (PP) melt-extruded with different amounts of as-grown carbon nanofibers (CNFs) from 0 to 1.4 vol. % are examined. The PP/CNF composites present CNF aggregates randomly distributed within the PP and an insulator–conductor transition at CNF contents near 0.9 vol. %. The degree of crystallinity of PP/CNF composites with loadings of 1.4 vol. % increases ∼15% with respect to the neat PP (∼34%), with σ´ ∼ 8.6 × 10−5 S m−1 (σ″ ∼ 8.3 × 10−4 S m−1) at 2 MHz. In addition, the values of the electrical conductivity σint´ ∼2.9 × 10−6 S m−1 (σint″∼3.7 × 10−4 S m−1) at 2 MHz, as a result of the interphase (ϕint ∼0.05 vol. %) of the 1.4 vol. % PP/CNF composites, are estimated by the use of a modified generalized effective medium model (GEM). The analysis gathered in here indicates that the interphase between the polymer and the conducting particle may have a quantifiable effect on the electrical properties of carbon-based polymer composites, and this fact should not be neglected in the production of conducting polymer composites (CPCs) with enhanced electrical properties.This study was funded by FCT-Foundation for Science and Technology: “Plurianual” 2020–2023 Project UIDB/00264/2020

Dielectric spectroscopy of melt-mixed polypropylene and pyrolytically stripped carbon nanofiber composites

In this work, pyrolytically stripped carbon nanofiber (CNF) polypropylene (PP) composites were synthesized following a scalable melt-mixing method, and the effects of CNF weight concentrations on the electrical conductivity, dielectric permittivity, electrical modulus and electrical impedance of PP/CNF composites were studied. Quite unexpectedly, the electrical conductivity of PP/CNF composites improved only slightly as the incorporation of CNFs was raised, yielding a maximum of ~10−10 S m−1 for PP/CNF 5 wt. % composites. The increase corresponded to a gradual improvement of the dielectric constant up to a maximum of ~9 for PP/CNF 5 wt. % composites at 1 MHz, which was attributed to the raise of interface polarization effect. Moreover, the Cole–Cole model was used to analyze the effects of CNF concentrations on the dielectric relaxation of PP/CNF composites, from which was deduced that the incorporation of CNFs increases their dielectric strength and relaxation times. The analysis gathered here aims to provide a better insight into the enhanced dielectric properties observed in low-conducting polymer composites filled with CNFs.A. J. Paleo gratefully acknowledges support from FCT-Foundation for Science and Technology by the project UID/CTM/00264/2021 of 2C2T under the COMPETE and FCT/MCTES (PIDDAC) co-financed by FEDER through the PT2020 program and “plurianual” 2020–2023 Project UIDB/00264/2020

Electrical Properties of Polypropylene-Based Composites Melt-Processed with As-Grown Carbon Nanofibers

Electrical conductivity, dielectric permittivity, electrical modulus, and electrical impedance of polypropylene (PP) composites melt-processed with different contents of as-grown carbon nanofibers (CNFs) are studied. As expected, the electrical conductivity of PP/CNF composites increased as the incorporation of CNFs is raised in the polymer, yielding a maximum of ∼ 6 ×10−6 S m−1 for PP/CNF 3 wt. % composites. That enhancement relates to a gradual improvement of the dielectric permittivity as the incorporation of CNFs rises into the PP up to a maximum of ∼ 13 for PP/CNF 3 wt. % composites at 1MHz, which is attributed to the rise of the interface polarization effect. Moreover, the Cole-Cole model is used through the electrical modulus to analyze the effect of CNF contents on the dielectric relaxation of PP/CNF composites from which is deduced that the incorporation of CNFs increases their heterogeneity and relaxation times. The analysis gathered here aims at contributing to the understanding of the electric features of polymer composites filled with a type of CNFs, which are not subjected to any thermal post-processing method after their synthesis by chemical vapor deposition (CVD)

Dielectric Spectroscopy of Melt-Mixed Polypropylene and Pyrolytically Stripped Carbon Nanofiber Composites

In this work, pyrolytically stripped carbon nanofiber (CNF) polypropylene (PP) composites were synthesized following a scalable melt-mixing method, and the effects of CNF weight concentrations on the electrical conductivity, dielectric permittivity, electrical modulus and electrical impedance of PP/CNF composites were studied. Quite unexpectedly, the electrical conductivity of PP/CNF composites improved only slightly as the incorporation of CNFs was raised, yielding a maximum of ~10−10 S m−1 for PP/CNF 5 wt. % composites. The increase corresponded to a gradual improvement of the dielectric constant up to a maximum of ~9 for PP/CNF 5 wt. % composites at 1 MHz, which was attributed to the raise of interface polarization effect. Moreover, the Cole–Cole model was used to analyze the effects of CNF concentrations on the dielectric relaxation of PP/CNF composites, from which was deduced that the incorporation of CNFs increases their dielectric strength and relaxation times. The analysis gathered here aims to provide a better insight into the enhanced dielectric properties observed in low-conducting polymer composites filled with CNFs