Preparation and characterization of polyacrylonitrile fiber precusor using multi-hole spinneret

Abstract

The aims of this study were to prepare and characterize polyacrylonitrile (PAN) fiber as a precursor for carbon fiber production. A dry-jet wet spinning technique with a multi-hole spinneret (10 holes, ? = 0.350 mm) and a solvent-free coagulation bath system were adopted in the preparation of PAN fibers precursor. The spinning dope consisted of polymer polyacrylonitrile (PAN) with acrylamide (AM) as an additive. Dimethylsulfoxide (DMSO) and dimethylformamide (DMF) were employed as solvent in the dope formulation. The dopes were prepared at 18 wt.% polymer concentration and coagulation bath temperature was varied between 13 °C to 20 °C. The PAN fibers were characterized using field emission scanning electron microscopy (FESEM), fourier transform infrared (FTIR), differential scanning calorimetry (DSC), thermogravimetry (TGA), x-ray diffraction (XRD) and tensile test. FESEM micrographs showed that at 18 wt.% of polymer concentration, PAN fibers prepared from DMF and DMSO exhibited similar circular cross-sectional structure with different fiber surfaces as coagulation bath temperature increased. Dope prepared from DMF resulted on PAN fibers with rough fiber surface meanwhile PAN fibers produced with DMSO showed smooth fiber surface. Both PAN fibers prepared from DMF and DMSO showed the presence of typical functional groups of precursor fibers particularly nitrile groups which is significant for higher processing temperature. The lowest weight lost was observed approximately 56 wt.% for PAN fibers prepared from DMSO. It showed a significant improvement of the polymer stability which enhanced the carbon yield. The highest glass transition temperature (Tg) recorded for PAN fibers fabricated from DMF was 92 °C and both PAN fibers from DMF and DMSO solvents exhibited the highest percentage of crystallinity which was 35 %. The mechanical properties of the prepared fibers are strongly dependent on the type of solvent used during the preparation. PAN fibers prepared from DMSO achieved the maximum of 279.20 kPa on tensile strength while maximum 3.25 GPa Young’s modulus obtained by PAN fibers prepared from DMF. This study concludes that different types of dope solvent and variation of coagulation bath temperature played significant role to determine the fiber structures and properties as well as fabricating PAN fibers via solvent-free coagulation system. The results also elucidate that dry-jet wet spinning technique with a multi-hole spinneret using solvent-free coagulation bath system with 18 wt.% polymer concentration produced PAN fibers continuously without any breakage thus enhanced the production of carbon fiber precursor.