Print version ISSN 0104-1428
LIMA, Aline M. F.; CASTRO, Vinícius G. de; BORGES, Raquel S. and SILVA, Glaura G.. Electrical conductivity and thermal properties of functionalized carbon nanotubes/polyurethane composites. Polímeros [online]. 2012, vol.22, n.2, pp.117-124. Epub Mar 13, 2012. ISSN 0104-1428. http://dx.doi.org/10.1590/S0104-14282012005000017.
Multi-walled carbon nanotubes (MWCNTs) functionalized with amine and carboxyl groups were used to prepare polyurethane/MWCNT nanocomposites in two distinct concentrations: a lower value of 1 mass% (spray coating) and a higher one of ~50 mass% (buckypaper based). The MWCNT-NH2 sample contained only 0.5 mass% of amine groups, whereas MWCNT-COOH contained 5 mass% of carboxyl groups. The MWCNT functionalized with low amine group content showed improved thermal properties when compared to neat thermoplastic polyurethane (TPU) and MWCNT-COOH based nanocomposites. The electrical conductivity of the polyurethane elastomer was greatly increased from 10-12 to ~10-5 S cm-1in the 1 mass% nanotube composite and to 7 S cm-1for the MWCNT-NH2 buckypaper-based nanocomposite. Furthermore, the relative high content of functional groups in the MWCNT-COOH sample, which disrupt the sp2structure in the nanotube walls, led to inferior properties; for instance the conductivity of the buckypaper based composite is one order of magnitude lower when using MWCNT-COOH in comparison with the MWCNT-NH2. These results show the range of property design possibilities available with the elastomeric polyurethane nanocomposite by tailoring the functional group content and the carbon nanotube load.
Keywords : Thermoplastic polyurethane; functionalized multi-walled carbon nanotube; spray coating; buckypaper.