An infiltration method for preparing single-wall nanotube/epoxy composites with improved thermal conductivity

Recent studies of SWNT/polymer nanocomposites identify the large interfacial thermal resistance at nanotube/nanotube junctions as a primary cause for the only modest increases in thermal conductivity relative to the polymer matrix. To reduce this interfacial thermal resistance, we prepared a freestanding nanotube framework by removing the polymer matrix from a 1 wt % SWNT/PMMA composite by nitrogen gasification and then infiltrated it with epoxy resin and cured. The SWNT/epoxy composite made by this infiltration method has a micron-scale, bicontinuous morphology and much improved thermal conductivity (220% relative to epoxy) due to the more effective heat transfer within the nanotube-rich phase. By applying a linear mixing rule to the bicontinuous composite, we conclude that even at high loadings the nanotube framework more effectively transports phonons than well-dispersed SWNT bundles. Contrary to the widely accepted approaches, these findings suggest that better thermal and electrical conductivities can be accomplished via heterogeneous distributions of SWNT in polymer matrices. (c) 2006 Wiley Periodicals, Inc.