A Comparison of Electrical Properties of Carbon Nanotube-loaded Resins

Increasing attention toward electromagnetic interference (EMI) in defense applications has resulted in initiatives to develop multifunctional materials that can satisfy structural performance requirements while effectively shielding electronic components from EMI. The goal of this article is to characterize the electrical properties of carbon nanotube (CNT) loaded resins with an emphasis on those properties that directly influence EMI shielding effectiveness; particularly conductivity. Limiting the measurements to conductivity allowed studying a wide range of candidate materials to identify the most promising combinations of overall cost, manufacturing process and materials. Various parameters affecting the conductivity of CNT-loaded resins were considered in this study from CNT characteristics (CNT loading as weight percentage and functionalization) and dispersion processes (sonication or microfluidization) used during fabrication. Electrical testing of specimens was conducted using a low-frequency impedance analyzer in order to measure the conductivity of manufactured CNT-loaded materials for a wide range of frequencies depending on the experiment. For the materials and conditions tested, the percolation threshold (CNT loading that produces a conductive material) was established to be approximately 0.3% by weight. Given the low percolation threshold, these results can be considered as a positive indication that CNT-loaded resins can be incorporated into conventional composites intended for load bearing applications and provide EMI shielding as well. An even more promising approach is to incorporate CNTs into composites using nanocomp-non-woven-fabric, which results in conductivities of 102 S/cm.