No abstract

A novel method for the continuous dispersion of carbon nanofibers (CNFs) in a polymer matrix for manufacturing high performance nanocomposites was developed using an ultrasonically assisted single screw extrusion process. The effect of ultrasound on die pressure, electrical and thermal conductivity, rheological, morphological and mechanical properties of polyetherimide (PEI) filled with 1 to 20 wt.% CNFs was studied. A reduction in the die pressure and percolation threshold of CNF/PEI nanocomposites with a permanent increase in the viscosity and a permanent decrease in tan d was achieved through ultrasonic treatment. Morphological studies of the treated nanocomposites revealed their improved homogeneity leading to an increase of the Young's modulus and electrical and thermal conductivity. 2 Experimental 2.1 Materials CNFs, Pyrograf-III, PR-19-HT, were provided by Applied Sciences, Inc., Cedarville, OH. These nanofibers are vapor grown and subsequently heated to temperatures up to 3000 8C REGULAR CONTRIBUTED ARTICLES Intern. Polymer Processing XXIII (2008) 4 Ó Carl Hanser Verlag, Munich 395 * Mail address: Avraam I. Isayev,

In situ compatibilization of immiscible blends of PEN and thermotropic LCP was achieved by the ultrasonically-aided extrusion process. Ultrasonicallytreated PEN underwent degradation, leading to a decrease of its viscosity. Viscosity of LCP was unaffected by ultrasonic treatment. Because of reduced viscosity ratio of PEN to LCP at high amplitude of ultrasonic treatment, larger LCP domains were observed in molding of the blends. LCP acted as a nucleating agent, promoting higher crystallinity in PEN/LCP blends. Ultrasonically-induced copolymer formation was detected by MALDI-TOF mass spectrometry in the blends. Ultrasonic treatment of 90/10 PEN/LCP blends improved interfacial adhesion in fibers spun at intermediate draw down ratios (DDR), improving their ductility. The lack of improvement in the mechanical properties of fibers spun at high DDR after ultrasonic treatment was attributed to the disturbance of interfacial copolymer by high elongation stresses.

No abstract