UV-Based Dual Mechanism for Crosslinking and Stabilization of PAN-Based Carbon-Fiber Precursors
Improvement in the stabilization step during production of carbon fibers is vital to making such high performance fibers cost competitive. This chapter summarizes a potential approach that utilizes a rapid, dual-stabilization route for the polyacrylonitrile (PAN) precursor fibers. A diethylaminobenzophenone was added as an external photoinitiator to PAN solution before the fiber wet-spinning step. After a short UV treatment, which induced partial cyclization and crosslinking at a lower temperature, precursor fibers could be rapidly thermo-oxidatively stabilized and successfully carbonized. Fast-thermal stabilized pure PAN-based carbon fibers showed hollow-core fiber defects due to inadequate thermal stabilization, but such defects were not observed for fast-thermal stabilized fibers that were UV treated (in the presence of the photoinitiator). No deterioration of interplanar spacing or decrease in crystallite size was observed within the experimental carbon fibers containing photoinitiator. Moreover, such fibers retained a higher extent of molecular orientation when compared with that of control fibers and displayed a higher tensile modulus than that measured for other sets derived only from thermal stabilization. These results establish for the first time the reduction of stabilization time and enhancement of modulus afforded by external photoinitiators/UV treatment of PAN-based carbon fibers.