Percolation behaviour of ultrahigh molecular weight polyethylene/multi-walled carbon nanotubes composites |
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Authors: | M.O. Lisunova Ye.P. Mamunya A.V. Melezhyk |
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Affiliation: | a Institute of Biocolloidal Chemistry named after F.D. Ovcharenko, NAS of Ukraine, 2, blvr. Vernadskogo, Kyiv 03142, Ukraine b Department of Applied Physics, National Aviation University, 1 Prospect Kosmonavta Komarova, Kiev 03058, Ukraine c Institute of Macromolecular Chemistry, National Academy of Sciences of Ukraine, 48 Kharkovskoe chaussee, 02160 Kiev, Ukraine d TM Spetsmash Ltd., Kiev, Ukraine |
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Abstract: | The electrical conductivity of polymer/multi-walled carbon nanotubes (MWCNTs) composites in a powder and in a hot-pressed compacted state, prepared by mechanical mixing, was studied. The semicrystalline ultrahigh molecular weight polyethylene (UHMWPE) was used as a polymer matrix. The data clearly evidence the presence of a percolation threshold φc at a very small volume fraction of the MWCNTs φ in a polymer matrix, φc ≈ 0.0004-0.0007. The ultralow percolation threshold in UHMWPE/MWCNTs thermoplastic composites was explained by high aspect ratio of the nanotubes and their segregated distribution inside the polymer matrix. The method of composite preparation effects the values of percolation threshold concentration φc and critical exponent t. A noticeable positive temperature coefficient of resistivity (PTC effect) was observed in the region of temperatures higher than melting point. It was explained by influence of thermal expansion of the polymer matrix and independence from the melting process that is a result of specific structure of conductive phase. |
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Keywords: | Conductive composites Carbon nanotubes Positive temperature coefficient Percolation |
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