Correlation between fibril structures and mechanical properties of polyacrylonitrile fibers during the dry‐jet wet spinning process

Abstract

ABSTRACTThe high quality polyacrylonitrile (PAN) fibers, which were used to manufacture the high performance carbon fibers, were prepared by the dry‐jet wet spinning process. The fiber samples were treated by using the ultrathin sectioning and solution etching methods. Subsequently, the changes of the fibril structures and mechanical properties were investigated by utilizing scanning electron microscopy, high‐resolution transmission electron microscopy and mechanical tester. The fiber titer and diameters, the amount of the pores decreased during the spinning process. The microfibrils were oriented along the fiber axis to form the fiber backbone in PAN fibers. Furthermore, the microfibrils with small size were incorporated into the large fibrils and some fold chains formed the interfibril transverse joint bridges to reinforce the connection of the fibril elements. The fibrils served as self‐reinforcing element to efficiently resist the cracks propagation and dissipate much energy to increase the tensile strength and initial modulus. Consequently, the PAN precursor fibers with the homogeneous, compact, well‐oriented, and closely interlinked fibrils, presented high tensile strength and initial modulus. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47336.