| In order to improve the dispersion and the interaction between single-walled carbon nanotubes (SWNTs) and polyacrylonitrile (PAN) matrix and to obtain high performance PAN nanofiber, the nanofiber sheets with well-aligned, smooth surface, and uniform diameter distribution were made from polyacrylonitrile (PAN) with polymer-wrapped single-walled carbon nanotubes (SWNTs) in different concentrations. The electrospinning preparation conditions were selected as the roll rotating speed of 2500 r/min, 14-16kV voltage, flow speed 0.3 ml/h. Then, the nanofibers sheets were hot-stretched along the fiber alignment direction under a certain tension and temperature to achieve the nanofibers with excellent mechanical properties.Scanning electron microscopy (SEM), Transmission electron microscopy(TEM), Thermal gravimetric analyzer (TGA), Differential scanning calorimetry (DSC), Polarized Fourier transform infrared spectroscopy (FTIR), X-ray diffraction, tensile test were used to characterize the microstructures and mechanical properties of nanofiber sheets. The results are as following:(1) The tensile strength of the PAN/SWNTs sheets with the concentration of 0.75 wt% SWNTs increases the most. However, with the high concentration of SWNTs, both the tensile stress and tensile modulus decreased slightly because of the poor dispersion of SWNTs in PAN matrix.(2) The SEM, polarized FT-IR, X-ray diffraction spectroscopy were also used to investigate molecular orientation and crystallinity of the nanofibers. The result showed that the excellent alignment along the sheet axis after the hot-stretched process, and it also can be found that the alignment of the nanofibers became closer to parallel after hot-stretched. Also, the crystallinity and orientation factor(/) of the nanofiber increased 240.24% and 245.45%, respectively.(3) The tensile strength of PAN and PAN/SWNTs nanofibers before and after hot-stretching were characterized. The resulted showed that the improved crystallinity and orientation resulted in the enhanced tensile strength and tensile modulus, the introduction of SWNTs and by the hot-stretching process can enhance the mechanical properties of PAN nanofibers remarkably. |
