Plasticization for melt viscosity reduction of melt processable carbon fiber precursor

Fibers of polyacrylonitrile (PAN), or commonly referred to as acrylic fibers, are found to have many applications. Acrylic fibers are used as a textile medium for high quality and high performance yarns and fabrics, and also as the main supply of precursors for carbon fibers. The main reason of its use as carbon fiber precursor is that the polymer gives high mechanical properties with high carbon yield compared to other polymers. However, a major issue with current carbon fiber production from PAN is the use of a solvent spinning process for the preparation of polymer fiber precursor with hazardous solvents, and its safe reclamation. This study presents a solution by a solvent-free melt-spinning process with a copolymer produced from acrylonitrile (AN) with 1-vinylimidazole (VIM). A further significant improvement of the melt-spinning process is found with the additional use of a new oligomer as a plasticizer; the oligomer was prepared by polymerizing AN and methyl-2-(1H-imidazol-1-yl) acrylate (IA). The AN/VIM copolymer has glass transition temperature (Tg) of 115 °C but the plasticizer use lowers it to 75 °C. Thus, the oligomer plasticizer broadens the temperature range of melt-spinning processability. A carbon fiber prepared utilizing 8 wt% of the synthesized oligomer (Mn = 5 KDa) and high molecular weight base copolymer (Mn = 47 KDa), tensile strength of 1.9 GPa and modulus of 190 GPa have been achieved.