Correlations between Percolation Threshold, Dispersion State, and Aspect Ratio of Carbon Nanotubes

• Published in: Advanced functional materials Vol. 17; no. 16; pp. 3207 - 3215
• Main Authors: Li, J., Ma, P. C., Chow, W. S., To, C. K., Tang, B. Z., Kim, J.-K.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 05-11-2007; WILEY‐VCH Verlag
• Subjects: Aggregation; Carbon nanotube composites; Conductivity; Conductivity, electrical; electrical; Modeling
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.200700065

Critical factors that determine the percolation threshold of carbon nanotube (CNT)‐reinforced polymer nanocomposites are studied. An improved analytical model is developed based on an interparticle distance concept. Two dispersion parameters are introduced in the model to correctly reflect the different dispersion states of CNTs in the matrix—entangled bundles and well‐dispersed individual CNTs. CNT–epoxy nanocomposites with different dispersion states are fabricated from the same constituent materials by employing different processing conditions. The corresponding percolation thresholds of the nanocomposites vary over a wide range, from 0.1 to greater than 1.0 wt %, and these variations are explained in terms of dispersion parameters and aspect ratios of CNTs. Important factors that control the percolation threshold of nanocomposites are identified based on the comparison between modeling data and experimental results.
Experiments and modeling are used to study the effect of carbon nanotube (CNT) dispersions and aspect ratios on the percolation threshold of CNT–polymer nanocomposites. Four different processing conditions are used to achieve mixtures of individual CNTs and entangled bundles (see figure), and their electrical properties are characterized.