Investigation of Film Formation and Electrical Properties of PS Latex/MWCNT Nanocomposites

Abstract

This work has been dedicated to investigate the optical, film formation and electrical properties of polystyrene (PS) latex/multiwalled carbon nanotubes (MWCNT) (PS/MWCNT) nanocomposites depending on MCWNT content. Conductive PS/MWCNT composites were prepared based on latex technology. MWCNTs were first dispersed in an aqueous solution of polyvinyl pyrrolidone (PVP) and then mixed with PS latex dispersion at different amounts, varying in the range of (0–20) wt%. After drying, PS/MWCNT films were separately annealed above the glass transition temperature (Tg) of PS, ranging from 100 to 250 °C, for 10 min. The optical, film formation and morphological properties of these composites were investigated by UV–vis (UVV) technique and scanning electron microscopy (SEM). In order to monitor film formation behavior of these composites, transmitted light intensity, Itr, was measured after each annealing step. It was observed from the Itr data that the classical latex film formation occurred only for the composites with MWCNT content in the range of (0–7.5) wt%. Film formation stages were modeled and the corresponding activation energies were measured. Energy values demonstrate that the film formation process of PS/MWCNT composite films was unaffected by the MWCNT content because PS latexes present complete film formation on the top surface of composites. The surface conductivities of annealed films at 250 °C were measured and were found to increase dramatically above a certain fraction of MWCNT defined as the percolation threshold of conductivity, Rc. Since a continuous percolated MWCNT phase was formed, the electrical conductivities of these nanocomposites increased about 10 orders of magnitude compared with neat PS film. These composites consist of MWCNT bundles in PS matrix with very low percolation threshold (Rc = 1.5 wt%).