Innovative wet-spinning for manufacturing defect free PAN fibers: Electric current assisted process

Abstract

Wet spinning is a conventional spinning process for making fibers. Wet-spun Poly-acrylonitrile (PAN) fibers have become more important since the discovery of PAN fibers in the 1960s that they can be transformed into carbon fibers through heat treatment. However, significant progress has not been made in wet spinning since the wet spun PAN fibers were commercialized in 1949. A new process parameter, such as the electric current, has not been introduced and its effect on the final properties of the PAN fiber has also not been investigated.<br/> <br/> In this thesis, a new process, current-assisted wet-spinning, was developed, which is the first attempt in the world. The main idea of current-assisted wet-spinning was inspired by the electrospinning. In the electrospinning process, polymer solutions are continuously spun into nanometer-sized fibers without significant damage even at extremely high electric potential (tens of kV). Like electrospinning, the current-as-sisted process was carried out simply by applying electric potential to PAN solution in the existing wet-spinning process. Unlike electrospinning, the electric current in current-assisted wet-spinning process was several hundred microampere.<br/> <br/> The PAN fibers fabricated via the current-assisted wet-spinning process (EPANf) showed 20% higher mechanical properties than the PAN fiber fabricated via general wet-spinning process (GPANf). Various characterization methods were conducted for both samples to investigate the mechanism of improved mechanical properties in EPANf. It was revealed that the applied electric potential affected the coagulation<br/> environment in coagulation bath by forming ions in PAN solution, attracting more non-solvent (water). The more absorbed non-solvent in the PAN fibers (EPANf) minimized the enlargement of existing voids and nanocavitation during following drawing process, resulting in the enhanced mechanical properties of PAN fibers. Due to the simple set-up of current-assisted wet-spinning process, it is expected that the newly developed process can be applied to commercial wet-spinning process, offering new opportunities of innovating PAN fibers and their productions.