Abstract
Electrically conductive polymer composites are in high demand for modern technologies, however, the intrinsic brittleness of conducting conjugated polymers and the moderate electrical conductivity of engineering polymer/carbon composites have highly constrained their applications. In this work, super high electrical conductive polymer composites were produced by a novel hot embossing design. The polydimethylsiloxane (PDMS) composites containing short carbon fiber (SCF) exhibited an electrical percolation threshold at 0.45 wt % and reached a saturated electrical conductivity of 49 S/m at 8 wt % of SCF. When reducing the sample thickness from 1.0 to 0.1 mm by the hot embossing process, a compression-induced percolation threshold occurred at 0.3 wt %, while the electrical conductivity was further enhanced to 378 S/m at 8 wt % SCF. Furthermore, the addition of a second nanofiller of 1 wt %, such as carbon nanotube or conducting carbon black, further increased the electrical conductivity of the PDMS/SCF (8 wt %) composites to 909 S/m and 657 S/m, respectively. The synergy of the densified conducting filler network by the mechanical compression and the hierarchical micro-/nano-scale filler approach has realized super high electrically conductive, yet mechanically flexible, polymer composites for modern flexible electronics applications.
Highlights
The development and popularity of smart electronics have attracted increasing demands for high performance and mechanically flexible electrically conducting polymer composites
For φ ≥ φcontaining short carbon fibers was investigated as a function of filler concentration or mechanical compression, and the effects of an additional where σ is the electrical conductivity of composites, σ0 is a constant that is typically assigned to the nano-scale filler (CNT, G, or CCB) on the electrical properties of the composites were discussed
The electrical conductivity of the composites near the percolation threshold follows a power-law relationship described in Equation (1), σ ∝ σ0 ( φ − φc )n, for φ ≥ φc where σ is the electrical conductivity of composites, σ0 is a constant that is typically assigned to the plateau conductivity of fully loaded composites, φ is the filler weight content, φc is the weight ratio of the filler at the percolation threshold, and the value of critical exponent (n) depends on the system dimension and is used to interpret the mechanism of network formation
Summary
The development and popularity of smart electronics have attracted increasing demands for high performance and mechanically flexible electrically conducting polymer composites. To promote the maximum electrical conductivity of polymer composites, we proposed a spatial confining forced network assembly (SCFNA) method to increase the packing density of the conducting network in the composites by mechanical compression [8,33,34], which reduced the separation distance between the fillers by excluding the insulting polymer phase out of the network. This mechanical compression approach effectively enhanced the electrical conductivity of polypropylene/short carbon fiber (SCF). PDMS with a trade name of SYLGARD 184, obtained from DOW CORNING (Midland, MI, USA), was
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