Plasticization for melt viscosity reduction of melt processable carbon fiber precursor

Abstract

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 (T g) 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 = 5KDa) and high molecular weight base copolymer (Mn = 47KDa), tensile strength of 1.9 GPa and modulus of 190 GPa have been achieved.

Progress of Fiber-Reinforced Composites

“…According to the literature, despite the fact that chemical modifications of lignin have been investigated [24], there are no references of successful melt-spun lignin conjugation with high molecular weight commercial spinnable polymers, using esterification after a chlorination reaction, so as to enhance the intermolecular bonds between the compounds. The successful chemical synthesis, which was conducted in this study without the use of plasticization [66] and confirmed by characterization, provided thermal process ability to the precursor fiber. Anthracene-oil-derived pitches as precursors have led to green carbon fibers [67], but the diameter of the fibers varied depending on the winding speed, and overall, that method was more expensive than using lignin in the blends.…”

Synthesis and Processing of Melt Spun Materials from Esterified Lignin with Lactic Acid

“…According to the literature, despite the fact that chemical modifications of lignin have been investigated [24], there are no references of successful melt-spun lignin conjugation with high molecular weight commercial spinnable polymers, using esterification after a chlorination reaction, so as to enhance the intermolecular bonds between the compounds. The successful chemical synthesis, which was conducted in this study without the use of plasticization [66] and confirmed by characterization, provided thermal process ability to the precursor fiber. Anthracene-oil-derived pitches as precursors have led to green carbon fibers [67], but the diameter of the fibers varied depending on the winding speed, and overall, that method was more expensive than using lignin in the blends.…”

Preparation and Characterization of Polyethylene Copolymers with PAH Side Groups as Carbon Fiber Precursors

“…Considering the melt-processability, a precursor with a liquid-like behavior and low viscosity at the processing temperature is typically favorable . Although a higher processing temperature would lower the viscosity of the CF precursor facilitating fiber spinning, a crosslinking reaction is expected as well due to the thermal-induced polycondensation between PAH side groups.…”

“…Considering the melt-processability, a precursor with a liquid-like behavior and low viscosity at the processing temperature is typically favorable. 55 Although a higher processing temperature would lower the viscosity of the CF precursor facilitating fiber spinning, a crosslinking reaction is expected as well due to the thermal-induced polycondensation between PAH side groups. Since the crosslinking reaction lowers the melt-processibility, the undesirable chemical reactions prior to the carbonization step need to be minimized under well-defined process conditions.…”