Multiwalled carbon nanotubes (MWNTs) were oxidated and functionalized in order to determine the structural and chemical changes on their atomic bonding. MWNTs were oxidized in an aqueous solution of HNO 3 (70%) and H 2 SO 4 (95%) at 25 °C. Pristine and oxidized carbon nanotubes (ox-MWNTs) were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and thermogravimetrical analysis (TGA). MWNTs and ox-MWNTs were silane-functionalized and incorporated into a polymethyl-methacrylate (PMMA) matrix. The dispersion properties and interface interactions were studied for the composite materials. MWCNTs oxidation was performed and supported by Raman spectroscopy and FTIR results of disorder and defects in the carbon lattice; as well as change in the amount and type of chemical groups attached to the CNTs walls. Roughness areas visible in SEM images indicate Van der Waals interactions between CNTs and functionalization reagents. Control of the oxidation state can effectively direct molecular functionalization of a CNT sidewall. Composites showed good dispersion of filler; with the best one for oxidized-silane functionalized CNTs.

Composites of multiwall carbon nanotubes (CNT) at 1, 2, and 3 wt.% on a polypropylene–polyethylene random copolymer matrix were prepared by melt compounding CNT powder and by dilution of a commercial polypropylene masterbatch (PMB). While the shear viscosity shows similar behavior for both dilution modes, the differences in their elastic properties clearly show the effect of the addition method and the presence of the PMB. This also indicates the relevance of having a difficult to mix masterbatch to enhance the elongational viscosity of the composites for free wall applications such as fiber spinning and blown film. On the other hand, the 2 and 3 wt.% CNT composites from both addition modes have similar electrical conductive behavior, with values near the semiconductors’ range. TEM and SEM images show different states of dispersion for each source of CNT. The immiscibility observed in those images is the simplest explanation for the differences in the molten composites’ elastic properties due to direct CNT addition versus CNT addition by dilution of a PMB.