Abstract
Composites have been made from singleโwall carbon nanotubes in a polyethylene (PE) matrix, in which different methods of preparation were used to disperse the nanotubes. The study includes using either the refined pure nanotubes (PโNT) as the source, or the original silica supported nanotubes (SSโNT). SSโNT contained nanotubes still incorporated in and around the silica as originally grown. Composites were then made by (1) coprecipitation from a suspension of PโNT or SSโNT in a PE solution, or (2) by forming a polymerization catalyst from the SSโNT, and using it to polymerize ethylene, which ruptures and expands the silica as polymer builds up in the pores. Extrusion was also studied as a method of additional dispersion. Nanotubes were found to have a powerful effect on the melt rheology, increasing the low shear viscosity dramatically. Increasing the nanotube concentration also increased the flexural and tensile moduli, decreased the elongation, and increased the electrical conductivity. Consistent trends were observed from all of these diverse properties: SSโNT had a stronger effect than PโNT, and within the SSโNT group the choice of silica type also had a major effect. Polymerization was generally preferred as the method of dispersing the nanotubes. The conductivity, which in some cases was quite high, was found to be pressure sensitive. Conductive NT/PE composites could be molded into films or extruded into other shapes, or comolded with other PE. ยฉ 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009