Evolution of Structure and Property of Polyacrylonitrile Fibers During Continuous Stabilization Process

ABSTRACT During the production process of carbon fibers, the degree of stabilization significantly influences the quality of the final product and overall production efficiency. Although the technology is mature, a deeper mechanistic understanding of the microstructural evolution under industrial conditions is essential for achieving superior performance. In this work, we investigated the structural and property evolution during the continuous stabilization process of large‐tow carbon fibers under gradient temperatures and varying line speeds, closely mimicking industrial practice. The mechanical properties of the carbon fibers were systematically evaluated. Attenuated total reflectance infrared spectroscopy (ATR‐IR) and density gradient column measurements were employed to analyze the chemical structural transformations and density variations. The changes in microstructure and performance were analyzed using X‐ray diffraction and single‐fiber tensile testing. Furthermore, scanning electron microscopy (SEM) and optical microscopy (OM) were utilized to examine fracture surfaces and polished cross‐sections, revealing the skin‐core structure and providing evidence for the transformation of the fiber's crystalline structure. The results establish a correlation between the stabilization parameters and the structure‐properties of the fiber, providing mechanistic insights to optimize production parameters and improve the quality and productivity of carbon fibers.