Electron transport and ac electrical properties of carbon black polymer composites

Abstract

The dielectric behaviour of various carbon black polymer composites has been characterized by the critical frequency ωc denoting the crossover from the dc plateau of the conductivity to its frequency dependent ac behaviour. The critical frequency can be related to the dc conductivity using a power law, ωc∝σdcz, with the exponent z. Presently accepted models predict z to be greater than one when varying the filler content. However, in accordance with published experimental results this work shows that z is rather close to one indicating a nearly constant static permittivity. Furthermore, the above power law makes it possible to describe all investigated compounds using a single master curve ranging over ten decades of dc conductivity. These findings are explained by a qualitative percolation model based on electron tunnelling. Increasing the dc conductivity along the percolation curve does not require the establishment of more physical links between carbon black aggregates. Rather, new conduction paths of nearly the same lengths but with higher tunnelling probability due to smaller gaps satisfy the percolation theory. This scenario allows the number of capacitive gaps to be nearly constant making z near one.

Effects of charge trapping on the electrical conductivity of low‐density Polyethylene–Carbon black composites

“…9 Some authors have shown that the increase of the CB agglomerates can be related to the increase of the critical CB weight content and makes narrow percolation range. [7][8][9] A certain effect of morphology on the electrical behavior of composites was shown for the composites of polymer blends and CB. [7][8][9] Patnaik et al have studied electrical conductivity of HDPE-CB composites using Positron Annihilation Lifetime Spectroscopy and suggested existence of three different morphological domains with different free volumes.…”

“…[7][8][9] A certain effect of morphology on the electrical behavior of composites was shown for the composites of polymer blends and CB. [7][8][9] Patnaik et al have studied electrical conductivity of HDPE-CB composites using Positron Annihilation Lifetime Spectroscopy and suggested existence of three different morphological domains with different free volumes. 14 In our experiments, LDPE as a crystalline branched polymer has a morphology with the possibility of formation of structural parts in percolation range.…”

“…This percolation threshold is usually of the order of 0.1-0.2 in volume fraction. 7 The level of conductivity of the polymer-CB composite can be varied by over 10 orders of magnitude depending on several factors. Among these we can mention CB content, specific conductive properties of CB, surface free energy and morphological properties of the polymer, processing conditions which mainly affect the degree of CB dispersion in the polymer matrix.…”

Micropatterning and Impedance Characterization of an Electrically Percolating Layer‐by‐Layer Assembly

“…Based on previous transmission electron micrograph results [19,42], the incorporated CB volume fraction (ca. 30 -40 vol%), and allowable tunneling distances [42,43], we anticipate the average particle spacing to be on the order of the particle diameter. In other words, the LbL film could be represented as a series of electrodes separated by 10 -30 nm gaps that are filled with electrolyte solution and a polyelectrolyte matrix.…”

Transport of carboxyl-functionalized carbon black nanoparticles in saturated porous media: Column experiments and model analyses

“…For a particle density of CBNPs, η was calculated using 1.80 g cm −3 obtained from the literature (Jäger et al, 2001). Sticking efficiency can be determined from the following equation (Tufenkji and Elimelech, 2004):…”