Effect Of Fiber-Forming Conditions On The Structure Distribution Of Pan Fiber

High-quality PAN fiber is a crucial precursor for high-performance carbon fibers. In the process of PAN fiber forming, spinning dope is ejected from the spinning holes into a coagulation bath, so the circumstance of the filament has a substantial effect on the process of double diffusion and phase separation. The solidification molding conditions are keys regulator of the structure of PAN fibers.In previous papers, PAN molecular structure and aggregation structure were studied using XRD, orientation structure were studied using XRD and sound velocity method, the radial structure of fiber were observed by optical microscopy and scanning electron microscopy. These traditional testing methods all study the overall structure of the fibers, the itself finer structure of the fiber in different preparing methods cannot be detected. Dissolution method is a new method to research fibrous structural differences. This issue establishes research methods PAN nascent fibers fine structure, get the structural features of the individual component, and calculates the component difference of fibers in the different coagulation bath conditions series, which provides some reference to the PAN fiber spinning process.Structure parameters of undissolving fibers are measured. According to classification standard and the mass fraction of each component, the structural features of the various components in PAN fiber are following:the molecular mass of component A to component E increase sequentially; the (110) crystal plane (29° diffraction) appears, which indicates that the molecular structure chain of the fiber becomes longer and overall regularity increases; the topographical variations of the PAN fibers dissolving at different times in different concentrations of DMSO solution observing by optical microscopy and scanning electron microscopy, it is shown that the higher the concentration of in the DMSO solution, the stronger dissolving capacity, the time to reach dissolution equilibrium in different concentration of DMSO solution is respectively different. After reaching dissolution equilibrium, radial direction of PAN fiber dissolves equably, which illustrates each component of PAN fiber equally distributes inside.The effect of three coagulation conditions on the distribution of nascent fiber fine structure components is studied. It is shown that the lower coagulation bath temperature, appropriate coagulation bath concentration and higher coagulation draft is conducive to the formation of PAN nascent fiber which possesses the appropriate distribution of fine structure. In different processing condition, the PAN nascent fiber possesses different content of fine structure. Because of the content difference of fine structure, the carbon fiber going through pre-oxidation and carbonization shows different properties.