Processing and characterization of extruded drawn MWNT-PAN composite filaments

A process for melt mixing of carbon nanotubes in polyacrylonitrile, which is aided by addition of plasticizer is proposed and employed to extrude/draw filaments at various draw ratios and test them for a range of properties. Microscopic observations show that the nanotubes are evenly dispersed throughout the filament and that they are preferentially aligned along its axis. The extrusion/drawing process results in two fold higher draw ratios of the nanocomposite filament compared with the unfilled control, and the first is shown by wide-angle X-ray diffraction and by polarized Raman spectroscopy to possess higher crystalline and morphological orientation. Thermal analysis and measurements of electric conductivity and mechanical properties attest to the condition that the carbon nanotubes are engaged in π–π interactions with the nitrile groups and/or with their polymerized conjugated imine system. These interactions interfere with and reduce the mutual dipole interactions of the nitrile groups of the polyacrylonitrile, allowing the nanocomposite filaments to be stretched to higher draw ratios. The potential reinforcing effect of the carbon nanotubes is cancelled out by the loss of the original dipole interactions, resulting in lower mechanical properties. However, the interaction of the carbon nanotubes with the conjugated imine system offers potentially interesting electric properties.