Preparation of High-Quality Polyacrylonitrile Precursors for Carbon Fibers Through a High Drawing Ratio in the Coagulation Bath During a Dry-Jet Wet Spinning Process

Excellent poly(acrylonitrile-co-itaconic acid) (99/1) (PAI) nascent fibers, which have an important role in preparing high-quality precursors for carbon fibers, were prepared by a dry-jet wet spinning process. Their structures were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and an ultrasound solvent etching method, as well their properties being determined by a strength and extension meter and a fineness meter, both designed specifically for fibers. When a high drawing ratio, over 300%, was applied to the fibers in the dry-jet wet spinning coagulation bath, the molecular chains were easy to orient and regularly arrange, resulting in the relative crystallinity, crystal size and amorphous orientation degree of the nascent fibers being improved. The fibrils with large diameter were formed, increasing the bulk density with the overall porosity and pore numbers decreasing. Therefore, the nascent fibers had smaller diameters, higher strength, higher rupture elongation and smaller coefficients of variation. The optimum high performance PAI precursor fibers, with 0.59dtex in titer, 7.51cN/dtex in tensile strength, 7.9% in rupture elongation and the final carbon fiber with 5.54GPa in tensile strength, were obtained through a post-spinning treatment in which they were subjected to a high coagulation bath draw ratio and carbonization.