Direction Dependent Electrical Conductivity of Polymer/Carbon Filler Composites

Abstract

The method of measuring electrical volume resistivity in different directions was applied to characterize the filler orientation in melt mixed polymer composites containing different carbon fillers. For this purpose, various kinds of fillers with different geometries and aspect ratios were selected, namely carbon black (CB), graphite (G) and expanded graphite (EG), branched multiwalled carbon nanotubes (b-MWCNTs), non-branched multiwalled carbon nanotubes (MWCNTs), and single-walled carbon nanotubes (SWCNTs). As it is well known that the shaping process also plays an important role in the achieved electrical properties, this study compares results for compression molded plates with random filler orientations in the plane as well as extruded films, which have, moreover, conductivity differences between extrusion direction and perpendicular to the plane. Additionally, the polymer matrix type (poly (vinylidene fluoride) (PVDF), acrylonitrile butadiene styrene (ABS), polyamide 6 (PA6)) and filler concentration were varied. For the electrical measurements, a device able to measure the electrical conductivity in two directions was developed and constructed. The filler orientation was analyzed using the ratio σin/th calculated as in-plane conductivity σin-plane (σin) divided by through-plane conductivity σthrough-plane (σth). The ratio σin/th is expected to increase with more pronounced filler orientation in the processing direction. In the extruded films, alignment within the plane was assigned by dividing the in-plane conductivity in the extrusion direction (x) by the in-plane conductivity perpendicular to the extrusion direction (y). The conductivity ratios depend on filler type and concentration and are higher the higher the filler aspect ratio and the closer the filler content is to the percolation concentration.

Thermal Conductivity and Electrical Resistivity of Melt-Mixed Polypropylene Composites Containing Mixtures of Carbon-Based Fillers

“…In addition, such stacks may orient during the shaping process parallel to the sample surface. The shape and orientation of the particle agglomerates was not quantified in the present study; however, an orientation of the graphite particles in the in-plane direction was described in previous studies [53,54]. In case of filler orientation in the in-plane direction, the thermal conductivity will also be higher in this direction and significantly lower when measured through the plane (the direction of measurement in our study).…”

“…This discrepancy may result from the graphite agglomerate particles not having the assumed spherical shape but forming anisotropic stacks, as shown in SEM images of graphite powder in ref. [53]. In addition, such stacks may orient during the shaping process parallel to the sample surface.…”

“…This could be caused by the orientation of the fillers in the polymer matrix. As shown in Kunz et al [53], the CNTs in a compression molded plate of polymer/CNT composite are mainly aligned in the plane. Due to this filler orientation, a higher thermal conductivity in-plane compared to through-plane can be expected.…”

Lightweight Polymer-Carbon Composite Current Collector for Lithium-Ion Batteries

“…We recently published the attractive electronic properties of polymer-carbon composite foils (PCCF) based on PVDF polymer [21][22][23]. In this study, we present the processing, electrochemical stability and performance of a PVDF polymer carbon nanocomposite current collector, which can be extruded to a thin hermetic dense collector foil and processed in a roll-to-roll process.…”

Electrophysical Properties of Epoxy Composite Materials Filled with Carbon Black Nanopowder

“…Polymer composites containing electrically conductive filler have great potential for application in various fields, for example, for the creation of various sensors, antistatic shielding, and the protection against electromagnetic radiation, as well as it can be used in electronics and aerospace industry [2,3]. Carbon fillers, such as carbon nanotubes, fullerenes, graphene, carbon fibres, and activated carbon nanopowders, are often used for the fabrication of PCM with improved physical-mechanical [4][5][6] and electrically conductive properties [7][8][9]. Some authors note the prospect of using carbon black (CB) particles as filler for such materials [10][11][12].…”