Single‐walled carbon nanotube/ultrahigh‐molecular‐weight polyethylene composites with percolation at low nanotube contents

Abstract

AbstractTo mix single‐walled carbon nanotubes (SWCNTs) with a polymer and to achieve low percolation thresholds, a low‐viscosity liquid has been required in order to achieve sufficiently good dispersion. In this article, data are presented which show that percolation occurs at ∼0.14 wt % carbon nanotubes and the dispersion procedure does not involve dispersing the SWCNTs in a low‐viscosity liquid. Specifically, ultrahigh‐molecular‐weight polyethylene powder was mixed with a powder containing nanotubes and catalyst support, e.g., the powder contains 93% silica and 7% SWCNTs. The powder blend is compression molded into sheets using high pressure and temperature. Because of the very high viscosity of the resin, the nanotube/silica mixture largely stays segregated at the interface as shown by scanning electron microscopy. A significant drop in tensile properties (modulus, tensile strength, and elongation at break) occurs with filler incorporation. Non isothermal crystallization measurements indicate that this filler does not nucleate crystallinity when mixed in this manner; although there is a definite sharpening of the melt endotherm indicating that crystallites with smaller lamellar thicknesses are reduced significantly with filler addition. The addition of filler also slightly reduces the overall fractional crystallinity measured after a constant cooling rate. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers