| High-performance carbon fibers have characteristics of high strength, high modulus. The corresponding PAN precursors should have high degree of crystallinity and high degree of orientation. According to the production requirements of high-performance carbon fiber PAN precursors, PAN spinning solution should be in the direction of high AN content, high concentrations. Compared with conventional spinning methods, electrostatic spinning process has specific "bending instability" procedure, making electrospun fibers exhibit different characteristics from traditional fibers.the composition of electrospinning PAN carbon fiber precursors has important influences in fiber-forming, structural characteristics and thermal performance. A system study on the effects of different PAN polymer compositions on the structure and performance of electrospinning PAN carbon fiber precursors has a very important significance.Three kinds of as-electrospun PAN precursor nanofibers with different copolymers (AN, AN-co-IA, and AN-IA-MA) were prepared with a flowing water bath followed by stretching in water at97℃. Their morphologies, aggregation structures and thermo-chemical properties were tested by scanning electron microscopy (SEM), X-ray diffraction (XRD), fourier transform infrared spectrometer (FTIR) and differential scanning calorimetry (DSC). It was mainly focused on the effects of the composition on the structures and properties of electrospinning PAN carbon fiber precursors.The study revealed that:(1) Best conditions of spinning process conditions:High voltage was30kV. The collection distance was20cm. The flow rate of syringe pump was1.0ml/h and roller speed was130r/m1n.(2)Compared with the traditional fiber SAF (3K), electrospun PAN fiber had smoother surface, fewer defects, uniform diameter and had significant advantages in density, crystallinity and crystal orientation. Meanwhile the further improvement of aggregation structure of electrospun fiber, having a certain effect on the thermal properties of the fiber.(3) MA comonomer in traditional PAN fibers can improve the spinnability and the drawability of the spinning solution. The PAN ternary fiber has smaller diameter, high degree of orientation, and at the same time density and crystallinity decreased, MA little effect on the thermal properties of PAN fiber.(4)Comonomer MA in ternary PAN copolymer can improve the solubility, spinnability, and drawability, so the ternary PAN fiber had small diameter (195nm), high crystal orientation degree (84.7%) and chain orientation degree (64.7%), followed by binary PAN fiber. Homo-PAN fiber had high density (1.216g/cm3), high crystallinity (78.9%) and low shrinkage in boiling water (10.6%). Those of binary PAN fiber were very close to homo-PAN fiber. Comonomer IA in binary PAN fiber and ternary PAN fiber can improve thermal performance, comonomer MA in ternary PAN fiber had little influence in thermal performance of PAN fiber. The addition of comonomer IA was necessary for the improvement of thermal performance of PAN fiber. Comprehensive results showed that the electrospun homo-PAN fiber was compact, but its thermal performance remains to be further improved. Electrospun binary PAN fibers had perfecter aggregation structures, and its thermal performance was good. Hence electrospun PAN precursor fibers with IA as a second comonomer had a perfect aggregation structures and better thermal performance.(5)Compared the role of copolymer composition in conventional PAN fiber and electrospun PAN fiber. We can found, for traditional PAN fiber, the contain of IA and MA comonomer is essential for improvement of thermal performance and aggregation structure. For electrospun PAN fiber, IA is nacessary for the improvement of thermal performance. Electrospun PAN fiber free of MA comonomer can also get a better aggregation structure, which is specific decision fiber-forming mechanism of the electrospinning process. |
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