| Carbon fiber is predominantly made from polyacrylonitrile (PAN) based precursors where the fibers are wet spun in the presence of hazardous solvent that also adds to the cost of production because of expensive solvent recovery and solvent recycling processes. Use of melt processable precursor for carbon fiber has long been suggested as a solution for this problem for both environmental and economic perspectives. In this study a successful method for carbon fiber preparation from melt processable acrylonitrile-co-1-vinylimidazole (AN-VIM) carbon fiber precursor is presented. The copolymers of different molecular weights were synthesized and used for extrusion, annealing, stabilization and carbonization. Positive correlations were observed when the mechanical properties of as-spun, annealed, stabilized, and carbonized fibers were compared with molecular weights of copolymers. A carbon fiber having a high tensile strength (TS) of 1.9 GPa with Young's modulus (YM) of 196 GPa was prepared from a copolymer having a weight average molecular weight (Mw) of 37 KDa. These mechanical values met the current requirement by automobile industry (TS = 1.73 GPa, YM = 173 GPa). To further reduce the cost of carbon fiber production, a new terpolymer, acrylonitrile-co-1-vinylimidazole-co methyl acrylate (AN-VIM-MA) with molar feed ratio of AN: VIM: MA = 82.0: 1.6: 16.4 was synthesized and characterized for use as a melt processable carbon fiber precursor. Compare to AN-VIM copolymer (molar feed ratio, AN: VIM = 82:18; glass transition temperature, Tg= 116ºC, char yield = 42%), the new terpolymer (Mw = 128.4 KDa) shows lower glass transition temperature, (Tg=89 ºC), high char yield (49%), UV mediated thermal stabilization and carbonization capability. Additionally, environmentally benign synthesis by using water as a solvent of AN-VIM copolymer was explored and preparation melt extruded fibers were successfully demonstrated. |
