Comparison of microstructural evolution differences during dry-jet wet spinning and wet spinning for polyacrylonitrile precursor fiber

This study compared the microstructural evolution of polyacrylonitrile (PAN) fibers, which serve as precursors for carbon fibers, during both dry-jet wet spinning and wet spinning processes. Detailed analyses were performed on fibers at various key stages of these two spinning methods using a range of techniques: scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), wide-angle X-ray scattering (WAXS), and small-angle X-ray scattering (SAXS) and so forth. The main differences between the two schemes lie in the coagulation bath stage. After coagulations dry-jet wet spinning fibers display higher crystallinity (about 75%, compared to 55% for wet spinning), distinct yield behavior, and strain hardening during the tensile test. In addition, according to SAXS scattering patterns, pores in dry-jet wet spinning are mainly formed during the coagulation process, while in wet spinning, they are more likely to originate from subsequent stretching. However, qualitatively speaking, if we ignore the morphological differences of PAN precursor fibers from those two methods, as the spinning process progresses, the above differences gradually decrease. These findings provide novel insights and valuable guidance for optimizing the PAN fiber spinning process.