The EMI shielding efficiency (SE) of a composite material depends on many factors, including the filler's intrinsic conductivity, dielectric constant, and aspect ratio [2, 6], Thus, in the field of conductive fillers, the overall properties of CNTs such as high conductivity, small diameter, high aspect ratio, along with high thermo-oxidative stability and mechanical strength make them an excellent option to create a continuous conductive network in composites for high-performance EMI shielding materials at low filler concentration (at low percolation threshold).
According to EMI theory, filler with a higher aspect ratio and intrinsic conductivity should have a better EMI shielding performance in the same polymer matrix.
Moreover, weak binding of the nanostructure leads to low shear modulus, and tends to reduce the intrinsic conductivity
This fact is already known [19, 20] and can be explained by two reasons: (1) the functionalization process must generate defects in the outer walls of the nanotubes due to the breakage of C--C bonds, decreasing their intrinsic conductivity
, and (2) the strong chemical interface formed between amino-functionalized CNTs and the epoxy matrix leads to polymer wrapping around the dispersed nanotubes, insulating the nanotubes from each other.
As EMI depends strongly on both the intrinsic conductivity
as well as the spatial distribution of conductive filler, we hypothesize that this decreased shielding performance for our materials is associated with the distribution of nanotubes throughout the coating; these SWNTs form a percolated network as evidenced by the high conductivity, but the network appears to be heterogeneous based on the EMI shielding.
3] S/m, which suggests that the observed value may be near the intrinsic conductivity
of entangled MWCNTs and represent an ideal mode of conduction.
Under the proper conditions, the electrospinning process can produce submicron to nanoscale fibers by selecting a proper solvent and polymer concentration as well as controlling the intrinsic conductivity
, the viscosity, and the surface tension of the solution [4, 7].
As described by Garboczi and coworkers (19-21), the intrinsic conductivity of the conducting filler in an insulating matrix can be defined in analogy to the intrinsic viscosity as:
The intrinsic conductivity [[sigma]] has been determined by a linear extrapolation of the reduced conductivity to a volume content of [[empty set].
The electrical conductivity of conductive polymer compounds is generally determined from the filler volume fraction and intrinsic conductivity
values of the fillers.
0] is a proportionality constant which often resembles the intrinsic conductivity
of the filler (10-100 S/cm for carbon black), s is the power-law exponent (typically between 1.
Ka/Kn approaching 60 at draw ratio of 25 , indicating that the intrinsic conductivity