Effect of Filler Orientation on the Electrical Conductivity of Carbon Fiber/PMMA Composites

Abstract

Abstract:The electrical conductivity of extruded carbon fiber (CF)/Polymethylmethacrylate (PMMA) composites with controlled CF aspect ratio and filler fractions ranging from 0 to 50 vol. % has been investigated and analyzed. The composites were extruded through a capillary rheometer, utilizing either 1-mm or 3-mm diameter extrusion dies, resulting in cylindrical composite filaments of two different diameters. Since the average CF orientation becomes more aligned with the extrusion flow when the diameter of the extrusion dies decreases, the relationship between conductivity and average fiber orientation could therefore be examined. The room temperature conductivities of the extruded filaments as a function of CF fractions were fitted to the McLachlan general effective medium (GEM) equation and the percolation thresholds were determined to 20.0 ± 2.5 vol. % and 32.0 ± 5.9 vol. % for the 3-mm (with CFs oriented less) and 1-mm (with CFs oriented more) filaments, respectively. It turned out that the oriented CFs in the composite shift the percolation threshold to a higher value, however, the conductivity above the percolation threshold is higher for composites with oriented CFs. A novel approach based on the Balberg excluded volume theory was proposed to explain this counterintuitive phenomenon.

Modeling Electrical Percolation to optimize the Electromechanical Properties of CNT/Polymer Composites in Highly Stretchable Fiber Strain Sensors

“…This is because the composite with shorter CNT length requires more CNTs to compensate its short length by increasing the number of tunneling paths in a percolation network. As shown in the figure, all the conductance curves and percolation probability curves with respect to CNT volume fractions agree well with previous reports 9,36,37 . By defining the critical volume fraction to be a volume fraction at the probability of 0.5 in Fig.…”

Characterization of Reduced and Surface-Modified Graphene Oxide in Poly(Ethylene-co-Butyl Acrylate) Composites for Electrical Applications

“…For anisotropic composites where the flakes are nearly parallel to each other (Δ θ = 0°), the percolation threshold is much higher than for isotropic systems (Δ θ = 90°) where the particle orientation is completely random (see Figure 7). The underlying explanation we put forward is that the probability for an intersection between two flakes becomes larger when the fillers are more randomly oriented, resulting in percolated paths throughout the composite already at lower filler fractions [3,26]. Corresponding angular distributions were calculated from the SEM graphs, revealing that the experimentally measured Δ θ is around 10–30° for the composites with naked rGO and around 50–90° for the grafted rGOs with the longest PBMA chains.…”

“…Moreover, if hydrophilic inorganic nanoparticles, such as SiO 2 , Al 2 O 3 , or ZnO, are introduced directly into a hydrophobic polymer matrix, the particle miscibility and the adhesion between the particles and the matrix can easily become unsatisfying. Even though a proper surface modification of the nanofillers can significantly improve the dispersion [2,3], it is still a major challenge for scientists and material producers to obtain completely controlled dispersions.…”

Flexible Thermoelectric Materials and Generators: Challenges and Innovations

“…Another potential method is to develop organic/inorganic hybrids, including incorporating TE fillers into conductive polymers via ex situ and in situ synthesis, or by intercalating organic molecules into inorganic layered structures . In such organic/inorganic hybrids, inorganic fillers such as inorganic TE particles and carbon‐based nanomaterials can provide extra current pathways and in turn induce energy‐filtering effects in the flexible polymer matrix, while organic molecules can provide the desired flexibility for the inorganic host . For inorganic FTE thin films, continuous flexibility can be realized through either depositing inorganic TE thin films on flexible substrates using atomic deposition techniques, or applying CNT scaffolds or nanostructure tailoring to develop free‐standing inorganic FTE films.…”