Dispersing carbon nanotubes in polymer nanocomposites: detecting individually dispersed tubes

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Carbon nanotubes (CNTs) are used to make polymer composites conductive. Small amounts of CNTs (0.1-1 wt%) increase the conductivity by several orders of magnitude. The electrical percolation threshold depends strongly on the dispersion state of the CNTs in the polymer matrix. We have performed electrical conductivity measurements and used electron microscopy (TEM, SEM) and Raman spectral mapping as a function of DWNTs weight fraction to access the dispersion state. We find that the DWCNTs dispersion depends on loading and large agglomerates are formed. Direct current electrical measurements show a percolation at 0.3 wt% of DWNTs and a maximum electrical conductivity of 10-2 S/cm are measured at 0.8wt%. The interaction of the outer wall of the DWCNT with the matrix leads to significant changes in the Raman G band line shape. Using G band Raman spectral mapping we distinguish the regions rich in DWCNTs bundles from regions where DWCNTs are dispersed individually. The presence of large agglomerates in nanocomposites shows that the percolation threshold can be significantly reduced by improving the dispersion of the tubes. We will discuss the influence of PEEK semi-crystalline polymer matrix crystallisation, nanotube adherence, grain size and the effect of annealing on nanotube dispersion.

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Journal: TechConnect Briefs
Volume: 1, Nanotechnology 2011: Advanced Materials, CNTs, Particles, Films and Composites
Published: June 13, 2011
Pages: 12 - 15
Industry sector: Advanced Materials & Manufacturing
Topic: Materials Characterization & Imaging
ISBN: 978-1-4398-7142-3