Nanocomposite films based on polymer and carbon nanoparticles are expected to have excellent properties. However, the production of these nanocomposites requires good dispersion/exfoliation of the nanofillers that tend to form stable agglomerates through Van der Waals interactions. In addition, they are hydrophobic in nature, which hinders their dispersion in water and in aqueous polymer suspensions. The present work aims at the study of the dispersion of exfoliated graphite in water through non-covalent functionalization with modified pyrenes, the production of composites in aqueous suspensions of polyurethane, and the characterization of the composites produced in terms of nanoparticle dispersion, thermal, mechanical and electrical properties. Three types of exfoliated graphite, with different particle sizes, were used, as well as the oxide of one graphite type. In addition, the influence of the dispersion parameters was studied, such as time of ultrasound application, the concentration and type of surfactant and the concentration of graphite, in order to find the best dispersion conditions. The exfoliated graphite suspensions were characterized by UV-visible spectroscopy, and were characterized by optical and electron microscopies and Raman spectroscopy. Polyurethane films were produced using these suspensions by solvent evaporation and by automatic doctor blade technique. The mechanical, thermal and electrical properties of the films were measured, and the morphology was characterized by optical and electron microscopies. The sonication time was relevant for the dispersion level achieved, and the larger nanoparticles (lower surface area) required longer dispersion time to reach a significant dispersion. The dispersion level was observed to have a significant influence on the final mechanical properties of the composites.