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.
Highlights
Conductive polymer composites (CPCs) are widely used in many fields, such as antistatic materials, electromagnetic interference (EMI) shielding, sensor and conductors
The results show that a higher orientation of the carbon fiber (CF) leads to a higher percolation threshold
0–50 vol % CF/PMMA composites with different fiber orientations, but all other properties held
Summary
Conductive polymer composites (CPCs) are widely used in many fields, such as antistatic materials, electromagnetic interference (EMI) shielding, sensor and conductors. Several previous papers have reported that a more parallel filler alignment increases the electrical conductivity [16,17], which is intuitively in contrast to our observation that an increasing anisotropy results in a higher percolation threshold. (Normally a higher percolation threshold results in a lower electrical conductivity, assuming that the volume filler fraction is fixed). The electrical conductivities and percolation thresholds of composites extruded with 1 mm and 3 mm diameter, respectively, capillary rheometer dies are compared, using the same CF volume filler fraction and AR for both die diameters. Anisotropic 1-mm die composite (φc = 30%) Using this novel experimental strategy, the influence of pure fiber orientation was systematically examined more precisely than previously possible. The methodically derived experimental results enabled us to reveal the underlying explanation for the aforementioned strange phenomenon
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
