Polypropylene (PP) nanocomposites with multi-walled carbon nanotubes (CNT) were produced by a small-scale masterbatch melt dilution technique using five PP differing in melt flow index (MFI) and degree of maleination. PP used in a masterbatch has MFI = 12 (PP12), the others used PP which have MFI = 2 or MFI = 8. The state of CNT dispersion as assessed by melt rheological and morphological investigations indicated a better dispersion when using unmodified PP with MFI = 8 (PP8) and the masterbatch's PP,,. Electrical conductivity results showed nanotube percolation at contents between 1.1 and 2.0 vol %, whereas lower values were obtained for the matrices with the best dispersion, i.e., PP8 and PP12. The dependencies of the relative Young's modulus on the CNT content showed that the maleinization improved the interfacial interactions between the components, especially in the case of maleated PP with MFI = 8 (PP-MA(8)), but the better dispersion was prevented by the incompatibility between polar groups of PP-MA and the nonpolar origin masterbatch PP12. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113:2536-2551, 2009