Electrical and Rheological Percolation in Polystyrene/MWCNT Nanocomposites

• Published in: Macromolecules Vol. 40; no. 20; pp. 7400 - 7406
• Main Authors: Kota, Arun K, Cipriano, Bani H, Duesterberg, Matthew K, Gershon, Alan L, Powell, Dan, Raghavan, Srinivasa R, Bruck, Hugh A
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 02.10.2007
• Subjects: Applied sciences; Composites; Exact sciences and technology; Forms of application and semi-finished materials; Polymer industry, paints, wood; Technology of polymers; Solvent effect; Polydispersed polymer; Electrical conductivity; Electrical properties; Molten state; Carbon nanotubes; Experimental study; Fabrication property relation; Multiwalled nanotube; Concentration effect; Percolation; Styrene polymer; Nanocomposite; Rheological properties
• ISSN: 0024-9297; 1520-5835
• DOI: 10.1021/ma0711792

A systematic electrical and rheological characterization of percolation in commercial polydisperse polystyrene (PS) nanocomposites containing multiwall carbon nanotubes (MWCNTs) is presented. The MWCNTs confer appreciable electrical conductivities (up to ca. 1 S/m) to these nanocomposites at a concentration of 8 vol %. In addition to enhancing the electrical properties, even at small concentrations (ca. 2 vol %), MWCNTs significantly enhance the rheological properties of PS melts. At concentrations exceeding 2 vol %, a plateau appears in the storage modulus G‘ at low frequencies, indicating the formation of a percolated MWCNT network that responds elastically over long timescales. Network formation, in turn, implies a diverging complex viscosity vs complex modulus curve. A focus of this study is on the correlation between electrical and rheological properties at the onset of percolation. The experimental results indicate that the elastic load transfer and electrical conductivity are far more sensitive to the onset of percolation than the viscous dissipation in the nanocomposite. Sensitivity of the electrical and rheological percolations to two different solvents used in processing the nanocomposites has also been characterized.