c] are quite dependent on the degree of mixing and the morphology of the compounds in addition to the structure and the intrinsic conductivity values of the conductive particles themselves (9, 10).
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.
0]), which is close to the intrinsic conductivity of carbon black (on the o rder of 10 S/cm) at all temperatures.
Ka/Kn approaching 60 at draw ratio of 25 , indicating that the intrinsic conductivity
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.
The intrinsic conductivity
of this new molecular species has the power to revolutionize the manufacture of many products and open the door to the nano-world for a broad spectrum of industries.
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.
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: