Carbon fibers derived from UV‐assisted stabilization of wet‐spun polyacrylonitrile fibers

Abstract

ABSTRACTA rapid, dual‐stabilization route for the production of carbon fibers from polyacrylonitrile (PAN) precursor fibers is reported. A photoinitiator, 4,4′‐bis(diethylamino)benzophenone, was added to PAN solution before the fiber wet‐spinning step. After a short UV treatment that induced cyclization and crosslinking at a lower temperature, precursor fibers could be rapidly thermo‐oxidatively stabilized and successfully carbonized. Scanning electron microscopy micrographs show no deterioration of the microstructure or hollow‐core formation in the fibers due to UV treatment or presence of photoinitiator. Fast‐thermally stabilized pure PAN‐based carbon fibers show hollow‐core fiber defects due to inadequate thermal stabilization, but such defects were not observed in carbon fibers derived from fast‐thermally stabilized fibers that contained photoinitiator and were UV treated. Tensile testing results confirm that fibers containing 1 wt % photoinitiator and UV treated for 5 min display higher tensile modulus than all other sets of thermally stabilized and carbonized fibers. Wide‐angle X‐ray diffraction results show a higher development of the aromatic structure and molecular orientation in thermally stabilized fibers. No significant increase in interplanar spacing or decrease in crystals size were observed within the UV‐stabilized carbon fibers containing photoinitiator, but such fibers retain a higher extent of molecular orientation when compared with control fibers. These results establish for the first time, the positive effect of the external addition of photoinitiator and UV treatment on the properties of the PAN‐based fibers, and may be used to reduce the precursor stabilization time for faster carbon fiber production rate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40623.