Ultrasound assisted twin screw extrusion of polymer-nanocomposites containing carbon nanotubes

The unique morphology and strong intertube attraction between carbon nanotubes (CNTs) make the dispersion of CNTs challenging and hence limit its effective use. A novel method for the continuous dispersion of multi-walled carbon nanotubes (MWNTs) in a polymer matrix for manufacturing high performance nanocomposites was developed using an ultrasonically assisted twin screw extrusion process. Reduction of the die pressure and variation of the ultrasonic power consumption as a function of amplitude were measured at various MWNT loadings. The effect of ultrasound on theological, electrical, morphological and mechanical properties of polyetherimide (PEI) matrix and PEI-filled with 1-10 wt% MWNTs was studied. In the treated nanocomposites, the complex viscosity, storage and loss moduli were increased and damping characteristics were decreased as compared to untreated ones. Rheological and electrical percolations were found to be between 1 and 2 wt% MWNT loading. Ultrasonic treatment does not affect the electrical conductivity of nanocomposites. Mechanical properties such as Young's modulus and tensile strength were significantly increased with MWNT loading but moderately with ultrasonic treatment at high loadings and certain ultrasonic amplitudes. The morphology and state of dispersion of MWNTs were investigated by means of HRSEM. In the ultrasonically treated nanocomposites, the obtained micrographs showed excellent dispersion of MWNTs in PEI matrix. (C) 2008 Elsevier Ltd. All rights reserved.