Structure, thermal, and mechanical properties were investigated for composite materials of polypropylene (PP) and acetic group functionalized multi-walled nanotubes (FCNT) at FCNT concentrations of 0.1%, 0.5% and 1.0% by weight. Part of the composites were compatibilized with maleic acid anhydride grafted polypropylene (PP-g-MA) at concentration of compatibilizer of 3 wt.%. Researched compositions were laboratory made from masterbatches of PP/FCNT and PP/PPg-MA/FCNT solutions in o-xylene, which were sonificated, precipitated in methanol, dried and melt mixed with the same matrix of PP. The compositions were compression moulded in to film samples. Structure changes and the properties of composites were researched by the methods of tensile tests, differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier infrared spectrometry (FTIR), and the measurements of dielectric characteristics. Effect of FCNT concentration in compositions as well as the effect of PP-g-MA compatibilizer was researched in detail.