Determination of the relationship between foam morphology and electrical conductivity of polymer/carbon nanotube nanocomposite foams

摘要

The lightweight of porous nanocomposites makes them attractive materials for various applications such as thermal and sound barriers, shock absorbers, insulation, packaging, and their porous structure is very interesting in bone tissue engineering. Moreover, the incorporation of appropriate carbonaceous nanoparticles into polymeric foams contributes to the reinforcement of their mechanical performances but also renders them electrically conductive, consequently extending their potential interest in electromagnetic shielding (EMI) and electrostatic discharge (ESD) applications for instance. In this PhD thesis, we aim at designing various polymeric foams containing a conductive nanofiller (carbon nanotubes) and to identify the main morphological parameters (pore size, cell density, cell wall thickness,…) that affect and govern the final properties of the foams. In this work, the electrical conductivity of the foams is the main property investigated because it is governing their performances as materials for EMI absorbers, the main application targeted in this work. These important morphology/electrical conductivity relationships would indeed be very useful to guide the foam development towards the material with the best performances for the targeted applications.Two different foaming methods are used in this work: (i) the supercritical CO2 (scCO2) foaming technology and (ii) the freeze-drying process. The first technique enables to produce isotropic foams with spherical closed cells structures and the second one, oriented anisotropic foams with cylindrical open cells. The variation of the foaming parameters allows preparing foams with a large panel of morphologies required for the establishment of the structure/properties relationships. In parallel to this main objective, an improvement of the overall conductive performances of the nanocomposites foams is also investigated through the optimization of the foam morphology and the content in conductive nanofillers.