Correlation between orientation behavior of polyacrylonitrile precursor and structure of nascent fiber

Polyacrylonitrile (PAN) precursors with different orientation behaviors were prepared by changing the coagulation bath conditions such as concentration and temperature. The orientation structure of the PAN precursor was determined by the method of sound velocity. X-ray diffraction and optical microscopy were used to investigate the crystalline structure and morphological characterization of nascent fiber, and the correlation between orientation of precursor and structure of nascent fiber was established. The molecular chain orientation ability “a” was defined as the slope of the logarithmic fitting curve of the degree of orientation varying with the drafting ratio, and the relationship between “a” and the crystallinity of nascent fiber was studied. The results show that the higher crystallinity nascent fiber has, the lower drawing ability PAN precursor has, and the higher degree of orientation has under the same drafting ratios. The maximum drafting factor of polyacrylonitrile precursor is significantly affected by radial structure of nascent fiber, it reaches the local maximum when the coagulation bath concentration is 74%. The fiber with high solvent content has higher molecular chain orientation ability than the fiber with low solvent content. The molecular chain orientation ability of precursor increases with the crystallinity of nascent fiber.