Improved mechanical properties of aligned multi-walled carbon nanotube/thermoplastic polyimide composites by hot stretching

High heat resistance composites based on thermoplastic polyimide resin and aligned multi-walled carbon nanotube sheets have been developed using hot-melt processing method with a vacuum-assisted system. The horizontally aligned carbon nanotube sheets were produced from vertically aligned carbon nanotube arrays using drawing and press-winding techniques. Effects of processing conditions, carbon nanotube contents, and hot stretching on the mechanical properties of the composites were examined. The aligned carbon nanotube/thermoplastic polyimide composites were fabricated successfully at a temperature of 410℃ under 2 MPa pressure. The surface morphologies of the composites showed high alignment and dense packing of carbon nanotubes, and a good impregnation of the thermoplastic polyimide matrix into the aligned carbon nanotube sheets. The best mechanical properties of the aligned carbon nanotube/thermoplastic polyimide composites were achieved at the carbon nanotube volume fraction of about 50% in this study. Hot stretching of the aligned carbon nanotube/thermoplastic polyimide composites at the temperatures above the glass transition temperature and below the melting temperature improved the mechanical properties of the composites considerably.