Skin effect of conductive polymer composites observed by high-resolution solid-state NMR

High-resolution solid-state Nuclear Magnetic Resonance (NMR) combined with other investigations was applied to provide essential information on conductive polymer composites based on high-density polyethylene (HDPE) as matrix and multi-walled carbon nanotubes (MWCNTs) or silver nanoparticles (Ag-NPs) as fillers. All composites were prepared by melt mixing using an extrusion process and characterized electrically. By studying the general features of NMR spectra and the molecular dynamic from NMR relaxation parameters, it was possible to obtain structural information about the organization and dispersion of fillers. Due to the paramagnetic or conductive nature of the fillers, it was found that a loss of NMR signal occurred with increasing amounts of filler. In the case of Ag-NPs, this phenomenon was attributed to a skin effect caused by the conductive properties of fillers limiting the adsorption of radiofrequency.