Abstract
Graphene nanoplatelet (GnP)-filled polysulfone (PSU) cellular nanocomposites, prepared by two different methods—namely, water vapor-induced phase separation (WVIPS) and supercritical CO2 dissolution (scCO2) foaming—were produced with a range of densities from 0.4 to 0.6 g/cm3 and characterized in terms of their structure and electrical conduction behavior. The GnP content was varied from 0 to 10 wt%. The electrical conductivity values were increased with the amount of GnP for the three different studied foam series. The highest values were found for the microcellular nanocomposites prepared by the WVIPS method, reaching as high as 8.17 × 10−2 S/m for 10 wt% GnP. The variation trend of the electrical conductivity for each series was analyzed by applying both the percolation and the tunneling models. Comparatively, the tunneling model showed a better fitting in the prediction of the electrical conductivity. The preparation technique of the cellular nanocomposite affected the resultant cellular structure of the nanocomposite and, as a result, the porosity or gas volume fraction (Vg). A higher porosity resulted in a higher electrical conductivity, with the lightest foams being prepared by the WVIPS method, showing electrical conductivities two orders of magnitude higher than the equivalent foams prepared by the scCO2 dissolution technique.
Highlights
Multifunctional polymer nanocomposites have been the center of attention in the scientific community for the last decade due to their capabilities in providing combined thermal, acoustic mechanical, and weight reduction properties, among others [1]
The PSU-based microcellular nanocomposites, prepared using both supercritical CO2 dissolution (scCO2) dissolution and water vapor-induced phase separation (WVIPS), presented density values between 0.435 and 0.568 g/cm3, with evidence of variations related to the PSU and solvent proportions in microcellular nanocomposites prepared via WVIPS and PSU and Graphene nanoplatelet (GnP) concentrations
In the case of the microcellular nanocomposites prepared by scCO2 dissolution foaming, a clear change in trend appeared after 1 wt% GnP, while in the case of the microcellular nanocomposites prepared by WVIPS it was observed at 5 wt% GnP, showing that the WVIPS was more effective in providing a better GnP dispersion, which could be related to the lower viscosity of the medium in this method (NMP-based dissolution), when compared to that of melt-compounding required for preparing PSUCO2 samples
Summary
Multifunctional polymer nanocomposites have been the center of attention in the scientific community for the last decade due to their capabilities in providing combined thermal, acoustic mechanical, and weight reduction properties, among others [1]. Various studies have considered the creation of cellular materials using high-performance thermoplastics for cutting-edge industries, such as aerospace, electronics, or telecommunications. Among high-performance thermoplastics, polysulfone (PSU) has been considered due to its high thermal stability and inherent fire resistance; its excellent mechanical properties—namely, high strength and toughness; and its good environmental stress-crack resistance [2,3]. PSU-based cellular nanocomposites prepared by CO2 dissolution batch foaming [5,6,7,8,9]; continuous extrusion chemical foaming; and solution phase separation—in this last case, used for preparing PSU-based membranes [10], have been studied vastly. Various studies have been conducted on PSU cellular nanocomposites and membranes with carbon-based nanoparticles [11,12,13,14]; the study of such cellular nanocomposites with respect to their electrical conductivity has not yet been explored. Sánchez et al [15,16] presented promising results regarding the fabrication of carbon nanotube and polysulfone thick-film screen-printed electrodes for electrochemical enzyme biosensor and immune-sensor applications
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