Chemically enhanced wet-spinning process to accelerate thermal stabilization of polyacrylonitrile fibers

In this study, a fast and inexpensive approach is introduced to assist stabilization of polyacrylonitrile (PAN) fibers by adding ammonium iron(II) sulfate in coagulation bath. Effects of chemical treatment on stabilization process and structural evolution of fibers are studied using calorimetric, infrared, and X-ray techniques. A stepwise infrared study confirms the assisted cyclization reaction, and an X-ray analysis reveals a significant improvement in crystallinity and orientation of polymer chains which lead to an increase in tensile strength and modulus of PAN fibers. Differential scanning calorimetry results show 13 °C reductions in peak temperature of the stabilization reaction which means a sign of chemical activation at lower temperature by adding sulfate ions. Quantification of IR spectra shows a 7% increase in extent of reaction of chemically treated fibers and higher degree of conjugation compared with untreated and post-treated fibers. Finally, mechanical properties of chemically treated fibers are improved due to an increase in size and orientation of polymer chains after chemical treatment in the coagulation bath. Compared to control and post-treated PAN fibers, thermochemical properties of presented fibers are improved due to chemically assisted stabilization, and as a consequence, energy consumption of the stabilization step will be reduced by a simple and facile treatment.