Dual percolations of electrical conductivity and electromagnetic interference shielding in progressively agglomerated CNT/polymer nanocomposites

Abstract

Recent experiments have revealed two distinct percolation phenomena in carbon nanotube (CNT)/polymer nanocomposites: one is associated with the electrical conductivity and the other is with the electromagnetic interference (EMI) shielding. At present, however, no theories seem to exist that can simultaneously predict their percolation thresholds and the associated conductivity and EMI curves. In this work, we present an effective-medium theory with electrical and magnetic interface effects to calculate the overall conductivity of a generally agglomerated nanocomposite and invoke a solution to Maxwell’s equations to calculate the EMI shielding effectiveness. In this process, two complex quantities, the complex electrical conductivity and complex magnetic permeability, are adopted as the homogenization parameters, and a two-scale model with CNT-rich and CNT-poor regions is utilized to depict the progressive formation of CNT agglomeration. We demonstrated that there is indeed a clear existence of two separate percolative behaviors and showed that, consistent with the experimental data of poly-L-lactic acid (PLLA)/multi-walled carbon nanotube (MWCNT) nanocomposites, the electrical percolation threshold is lower than the EMI shielding percolation threshold. The predicted conductivity and EMI shielding curves are also in close agreement with experimental data. We further disclosed that the percolative behavior of EMI shielding in the overall CNT/polymer nanocomposite can be illustrated by the establishment of connective filler networks in the CNT-poor region. It is believed that the present research can provide directions for the design of CNT/polymer nanocomposites in the EMI shielding components.

Bio-Based Poly(Imine-Amide) Materials with Dynamic Covalent Adaptable Networks: Toward Conductive Composites and Thermally Moldable Microcellular Foams

“…The low φ c and high electrical conductivity values for D3C7/MWCNT nanocomposites can be explained by the dual-percolation model. The theory of dual percolation is based on the phenomenon that conductive fillers can be unevenly distributed in the multiphase polymer system of the polymer because a specific phase in the polymer has a relatively good affinity with the conductive filler. ,, Therefore, the dual-percolation phenomenon greatly promotes the formation of a macro-conductivity network and greatly reduces the percolation threshold of the composite material. The results of this study show that high conductivity is related to a low imine ratio in PIAs, indicating that the conductive filler preferentially fills with DAV in the imine phase because it has a higher affinity with MWCNTs than with amide networks.…”

Polymer Nanocomposite Based on Pyrolyzed Polyacrylonitrile Doped with Carbon Nanotubes: Synthesis, Properties, and Mechanism of Formation

“…The next generation of absorbing materials will allow reducing mutual interference between devices operating in the radio and nearinfrared ranges [12]. We see that there is an urgency for theoretical and practical studies of the basics of synthesis and physical properties of improved nanocomposite nanomaterials that can provide high efficiency of absorption or reflection of electromagnetic radiation in the barrier band of the device [15][16][17][18][19][20].…”