Processing and Characterization of the Polymer/CNTs Nanocomposite Fibres.

Some specific properties of carbon nanotubes, CNTs, such as their fibrous structure, low density, high aspect ratio, extraordinary mechanical properties, make them particularly attractive fillers for the fabrication of polymer/carbon nanotubes nanocomposites. Traditional methods for the formulation of nanocomposites are: in situ polymerization, solution blending and melt mixing. The latter, as reported by Cipriano et al.[1], leads to the loss of the conductivity of CNTs, but this could be recovered through melt annealing at temperatures above the polymer’s glass transition temperature (Tg). Some innovative nanocomposite preparation techniques, such as solid-state shear pulverization and latex technology, allow achieving better dispersion of CNTs within the polymer matrix, compared to traditional methods and, therefore, allow making nanocomposites with improved properties. The results obtained adding low weight percentages of CNTs keep very far from the theoretical predictions made on the basis of the rule of mixtures or the Halpin-Tsai model. Furthermore, the achievement of the percolation threshold and uniform dispersion of CNTs are essential conditions for the development of nanocomposites with superior properties in comparison to those of the pure matrix [2-5]. Few papers are available in the literature regarding the rheological behaviour of polymer/CNTs systems. These report that the addition of CNTs has a substantial influence on the viscosity values only at low frequencies, while at high frequencies the effect is quite poor [5-8]. Wang et al. [6] reported, on Ny6/CNTs system, that the nanocomposites showed higher viscosity and G’-G’’ moduli than those of the neat Ny6, and more pronounced shear thinning. Moreover, the nanocomposites showed a transition from liquid-like to solid-like behaviour upon increasing CNTs loading. There are not papers available in literature about the characterization of polymer/CNTs systems subjected to elongational flow. The main purpose of this work is the preparation of polymer /CNTs systems based on PS, PA and EVA, at two different CNTs percentages (in particular, 1 and 3% by weight) and the rheological and mechanical characterization of drawn fibers as a function of draw ratio. The rheological and morphological studies performed on these systems allowed the correct interpretation of the obtained mechanical properties results.