Dispersion of carbon nanotubes in polypropylene: a comparative investigation by optical microscopy and terahertz time-domain spectroscopy

The degree of dispersion of nanosized fillers in a polymer based matrix strongly influences the ultimate properties of nanostructured systems. In this contribution, melt compounded polypropylene (PP) based systems containing 0.5 % in volume of not functionalized, carboxyl- and amino-functionalized multiwalled carbon nanotubes (MWCNTs) have been analyzed by optical microscopy and high frequency spectroscopy. Results, confirming the influence of the interface chemical features on the achieved filler dispersion, highlighted useful correlations between the typical dispersion index (D) obtained by optical microscopy tests and specific spectroscopic parameters as refractive index (n) and absorption coefficients (?) from high frequency tests.