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

Abstract

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.

Theoretical Prediction of Electrical Conductivity Percolation of Poly(lactic acid)—Carbon Nanotube Composites in DC and RF Regime

“…The behavior of the effective complex permittivity of conductive polymer composites (CPCs) is expected to be well predicted by the percolation model in the DC regime [21] as well as at low and high microwave frequencies [22,23]. Several theoretical models have been applied to predict the conductivity of the CPCs in order to check their validity and limitations [24].…”

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

“…On the other hand, because polypropylene (PP) is one of the most widely used commodity thermoplastics with adequate physical properties at low cost [15], the production of CPCs based on CNFs and PP by melt-mixing has been the subject of extensive investigation [16,17]. Notably, the broad dispersion of electrical conductivity reported for all these melt-mixed PP/CNF composites shows that the root causes of their electrical properties are far from being completely resolved [18]. Moreover, despite intensive research on the production and further analysis of carbon-based CPCs with outstanding electrical conductivities [5], research on low-conducting carbon-based polymer composites with enhanced dielectric properties is still limited.…”

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

“…In particular, due to their remarkably electrical conductivities (10 4 Sm À1 ), the production of conductive PP composites based on CNFs by melt-mixing has been the subject of investigation during the past few decades [9][10][11]. Notably, the broad dispersion of electrical conductivity values reported for meltprocessed PP/CNF composites shows that their electrical properties are far from being totally understood [12]. It is in this context that this study is conducted.…”

“…It is in this context that this study is conducted. Specifically, the analysis involving the improved dielectric permittivity of PP composites melt-processed with different contents of as-grown carbon nanofibers [12,13], which are not subjected to any thermal post-processing method after their CVD synthesis are revisited in this work. The effects of CNFs on the AC electrical conductivity and dielectric permittivity of PP/ CNF composites are detailed with the use of the electrical modulus formalism from which the phenomenological Cole-Cole model is utilized.…”

“…Figure 3.XRD patterns of PP/CNF composites and position of lines due to the phase α of melt-extruded PP (short dot lines are to guide the eye)[12].…”