Properties of polypropylene and polypropylene/poly(ethylene-co-vinyl alcohol) blend/CNC nanocomposites

Rheological, mechanical and thermal properties of polypropylene (PP)/cellulose nanocrystal (CNC) nanocomposites were compared with those of nanocomposites containing poly(ethylene-co-vinyl alcohol) used as a compatibilizer (CO). The nanocomposites were prepared by an internal mixer at a CNC content of 5 wt%. The complex viscosity and storage modulus of the nanocomposite sample containing the compatibilizer prepared by a solution method were increased at low frequencies, compared to those of the non-compatibilized nanocomposite samples. Moreover, a pronounced overshoot of the transient viscosity in a shear stress growth experiment was observed for the compatibilized nanocomposite. Scanning electron microscopy (SEM) showed the disappearance of large agglomerates when using the compatibilizer. The Young modulus of the nanocomposite samples containing the compatibilizer was increased up to ca. 47% compared to the neat PP. The elongation at break was decreased in all PP/CNC nanocomposite samples, but less for those containing the compatibilizer. The crystallinity of the PP in the nanocomposites and the crystallization temperature were increased after compatibilization. These results show that the poly(ethylene-co-vinyl alcohol) is an efficient compatibilizer that favors a better dispersion and wetting of the hydrophilic CNCs within the hydrophobic PP phase.