The Transition Of Molecular Agglomeration Structure Of Pan Fiber During The Spining Process

The mechanical properties of carbon fiber were determined by thestructure of PAN precursor. In other words, for the manufacture of highperformance carbon fiber, it is very important to get appreciate structurefor precursor by the adjustment of outfield factors. Such as thermal,tension and so on. Most of the previous literatures reported the structureof PAN fiber, independently, but there was little information about theinfluence of outfield factors during spinning process. The transition ofmacromolecular conformation for PAN fiber and its effect on theaggregation structure, which plays an important role in the structure ofPAN precursor was almost no report. Thus, it’s great significance to studythe microscopic structure including the evolution of chain conformationand aggregation structure during wet-spinning process.In this thesis, the IR method for characterizing the molecular chainconformation was established. In this way, the effect of the outfield on thechain conformation of PAN fiber was investigated. The analysis of aggregation structure during the spinning process was also performed.Based on the experiment data of fourier transform infrared spectroscopy(FTIR), X-ray diffraction (XRD), dynamic mechanical analysis(DMA), the structure evolution for PAN fiber during spinning processwas clarified from the microscopic viewpoint. The evolution model ofmicroscopic structure for PAN fiber was deduced.The results indicated that:(1) The chain conformation of PAN could be characterized by theparameter C, which was defined by C=I1230/I1250from the IRmeasurements. When the C value was increased, the statistic of31helixconformation was also increased. Otherwise, the statistic of planar zigzagconformation was relatively increased.(2) With the processing of the spinning process, the statistic ofplanar zigzag conformation was increased due to the complicatedoutfield.(3) During the cogulation process, with the higher concentration,the temperature or the tension, the rate of cogulation was slowed down,the statistic of31helix conformation was increased, the d-spacing of (100)miller plan was also increased,the crystallite size L100was increased.(4) The statistic of planar zigzag conformation of PANmacromolecular was increased by perform the higher tension, as well as the d100, L100and orientation degree.(5) By increasing the temperature, the statistic of31helixconformation was increased the d100and L100were also increased.In present study, the macromolecular conformation of PANprecursor and its effect on the aggregation structure were investigated, aswell as the evolution during spinning process. The effect of outfield, suchas thermal and tension was identified. Above all, the author believes thisstudy can contribute to the development of carbon fiber.