Polypropylene Carbon Nanotubes Nanocomposites: Combined Influence of Block Copolymer Compatibilizer and Melt Annealing on Electrical Properties

We study the influence of melt annealing and the presence of a block copolymer compatibilizer on the electrical properties of polypropylene carbon nanotubes (CNT) nanocomposites from the DC limit to microwave frequencies and link it to the morphological details. We show that the compatibilizer concentration controls three types of morphologies: separate CNT agglomerates, a network of well dispersed but interconnected CNT, and individualized but separate nanotubes. This explains why conductivity reaches an optimum over the whole frequency range at a low compatibilizer concentration. We model the corresponding structures by a semiquantitative schematic equivalent electrical circuit. A key outcome of the work is the understanding and control of dispersion mechanisms in order to optimize the electrical performances for efficient EMI shielding depending on the targeted frequency range.