Study On Formation And Evolvement Of Pan Fibers By Gel Coagulation Process

The high performance polyacrylonitrile precursor is the base to produce the high performance PAN-based carbon fiber. In the process of producing PAN precursor, the coagulation is the most important step. The gel coagulation is one kind of idealized coagulation pattern. Realized gel coagulation and mechanism of gel coagulation is a problem needed to settle.In this paper, PAN fiber is gained through wet-spinning. Adding some N into PAN spinning solution during polymerization, transparent and homogeneous as-spun fibers will get and it is the phenomenon of gel coagulation. This paper discusses the mechanism of N modified PAN spinning solution by UV spectrophotometry and revolving rheometer. Morphology and structure of the as-spun fibers produced by the N modified PAN spinning solution and the unmodified as-spun fibers are compared by means of scanning electron microscope (SEM) and X-ray diffraction (XRD). The paper also does further study on the influence of the difference to structure, morphology and thermal properties of the precursors. The results show that after adding N, PAN and DMSO association function become stronger and the association function between the precipitator H2O become weaker. This changes the diffusion of DMSO and H2O in the gelatin network, and presents gel coagulation phenomenon. Modifier N has increased the PAN spinning solution’s apparent viscosity, viscous flow activation energy and changed the spinning solution’s dynamic viscoelasticityThe N modified PAN spinning solution can produce better as-spun fibers. The modified PAN as-spun fibers’crystalline degree becomes larger and crystalline size smaller. The PAN precursor structure is developed from as-spun fibers. They have the similar crystalline structure and morphology. Crystalline size of the modified PAN precursor is smaller than the unmodified one. The modification mainly improves the double diffusion function of PAN spinning solution during coagulation. Its influence on the PAN precursor thermal properties is limited.