Study On Gelation Behaviors Of PAN Caron Fibre Precursor Solutions And The Spinning Of Its Fibers

Due to it’s a series of high performance, such as high strength, high modulus, heat-resistant, erosion-resistant etc., carbon fiber (CF) is an advanced material used widely in all kinds of fields. However, there are large gaps in the properties and production of polyacrylonitrile (PAN)-based carbon fiber between domestic and foreign countries. PAN precursors have been the key factor for producing carbon fibers. But currently, the holes and skin-core structure in the fiber formed during the spinning process, block the fibers’ high performance. Gelation in spinning process can solve this problem.In this paper, non-solvent additives(NSA) was added into the solutions, so that the PAN system became gelation in the spinning process. The spinning process conditions was also improved to obtain the PAN fibers with structural regularity. The content and the kind of small molecule gel accelerant NSA, the kind of solvent for solution, the homogeneity and stability, the effect of the temperature of gelation, the best technics conditions for spinning were investigated. The spun fibers’ micro-morphology, crystallizations were also investigated by SEM, XRD, DSC. The main results obtained are as follows:Adding an appropriate amount of different kind NSA (1#, 2#, 3#) in PAN solution is indeed the way to make the system generate solution-gel transition phenomenon. And choose DMSO as the solvent with an appropriate amount of 1# NSA in the solution can be easiest carried out for the currently conditions of spinning in industry.The viscous-elastic modulus (G\ G") of PAN solutions increased separately with the decrease of temperature or with the increase of the NSA content, and G’ change faster than G". We were able to determine the gel point by the intersection of G’ and G" of the solution, which was the temperature of solution began to gel.During steady shear flow measurement, the trend of the reological curves was not influenced by different NSA at different temperatures above the gel point temperature. Whether NSA was added into the solution or not, at lower shearing veloeity the reological curves went downwards with the increase of temperature. And the solution system was keep homogeneous state at different temperatures above the gel point temperature. These were helpful for the study of precursor solution preparation and its temperature control.By improving the spinning process conditions, the PAN fibers have been spun. SEM was used to characterise the micro-morphology of the fiber, and the results showed that there was no core-skin structure and holes in the fiber. The DSC and XRD test showed that the spun fiber was indeed obtained through solution-gel transition, and had no partial crystallization.