Study On Preparation Of Carbon Nanofiber Mats With High Strength From Electrospun PAN Precursors

Polyacrylonitrile (PAN) fiber is one of important industrialized polymeric fibers, and carbon fiber based on PAN precursor has the best comprehensive performance. Since the ultrafine carbon fiber has not only the structural features of carbon fiber but also the ultrafine diameter of nanofibers, it is highly valued in application areas such as carrier for catalyst, the anode material for lithium battery, capacitor electrode with double electrical layers and field electron transmit material and so on.In this paper, aligned polyacrylonitrile (PAN) nanofiber mats, as precursors of carbon nanofibers, were prepared by electrospinning and collected on a high-speed rotation drum. Before preoxidation and carbonization, moderate tension was applied to the PAN nanofiber mats. Finally aligned nanofiber mats with concentrated diameter distribution and high strength were obtained.As precursors, the form and performance of PAN electrospinning mats significantly affect the final productive carbon nanofiber mats. The concentration of the PAN/DMF solution and the parameter were determined in the initial electrospnning experiments. PAN electrospinning mats with different fibers parallel-degree were produced by a drum collector on corresponding rotation velocity. After the analysis of the SEM photos and the calculation of the parallel degree y, the correlation between the fibers parallel degree and the mechanical strength of the orientation PAN electrospinning mats was examined. Eventually, tensile strength measured 8.18 MPa, the PAN electrospinning mats with highest fibers parallel degree and strongest mechanical strength were produced on the rotation velocity of 906m/min. Preoxidize the orientated PAN electrospinning mats. DSC experiments were carried out with mats acquired under different preoxidization temperature. According to the DSC curves, the intra-molecular cyclization degrees of the different preoxidization samples were calculated through the thermo-chemical behavior of the macromolecules. The result revealed that 280℃was the optimal temperature.After cabonization, the electrospinning carbon nanofiber mats collected on the different rotation velocity were obtained. Compared with the PAN electrospinning fibers, the average diameter of the carbon nanofibers around 865nm decreased obviously, and the fibers parallel degree of the mats was not changed.The mechanical properties testing results revealed that the higher orientation carbon nanofiber mats had better mechanical strength and less peaks in stress-strain curves. Eventually, tensile strength measured 101.74 MPa, the carbon nanofiber mats with highest fibers parallel degree were produced on the rotation velocity of 906m/min.Parallel aligned PAN electrospinning mats had been obtained on the high-speed rotated drum. After the electrospinning, the mats were further stretched through the imposing tensions on. The PAN electrospinning mats were prepared after the further stretching processing, with higher orientation got shorter average diameter of fibers which fiber parallel-degreeγ, which was close to 1.The PAN electrospinning mats would get better tensile strength if further tensions were applied, maximum of 28.89 MPa, when the max tension was 1648KPa. After preoxidation and carbonization, also when the tensions preserved increased, the mechanical properties of the carbon nanofiber mats improved. Finally, tensile strength measured 184.47 MPa, the carbon nanofiber mats with highest fibers parallel degree were produced when the max further tension was 1648KPa.