Effects of different coagulation conditions on polyacrylonitrile fibers wet spun in a system of dimethylsulphoxide and water

Abstract

Polyacrylonitrile (PAN) precursors were prepared by the wet spinning way. The effects of the coagulation conditions, such as coagulation temperature, coagulation ratio, and coagulation concentration, are discussed in detail. While keeping the coagulation bath concentration constant, as the coagulation bath temperature increased, the cross section deviated less from a circular form, and the as-spun fiber diameter decreased. Measurement to the rate of the boundary movement has been calculated depending on the coagulation rate. While keeping the coagulation bath temperature constant, high coagulation bath concentration can cause more coagulant to diffuse into the solution to the polymer precipitated consequently, which led to a faster coagulation rate. The as-spun fiber from high coagulation concentration was compacted than those from low concentration. The character of the formed structure reflected the system mobility and capability to crystallize. Improvement in fiber density in the as-spun fiber resulted in improvements in the tensile strength of the as-spun fiber.

Properties of PAN Fibers Solution Spun into a Chilled Coagulation Bath at High Solvent Compositions

“…The fibers clearly show a change in fiber cross section from bean shaped to circular with increasing solvent concentration in the coagulation bath. This has been shown by numerous authors [5,[9][10][11]18] and is due to the formation of a skin on the fiber surface when spun into water-rich conditions, which encourage instantaneous demixing of the polymer dope jets. This skin remains as the filament core collapses during diffusion, resulting in a bean shaped fiber.…”

“…Large pockets and voids are seen in the fibers from a 57.8 wt% DMAc/H2O coagulation bath, while the 79.0 wt% DMAc/H2O bath produced a much more homogeneous fibril distribution, indicating higher overall density. It is known that the fibrillar structure formed during coagulation is carried through the remaining steps [2,8] and that improvement in the fiber density resulted in improvements in the fiber tensile strength [10]. …”

“…Few, if any, have focused on high solvent concentrations in the coagulation bath (>70 wt% solvent/non-solvent), with chilled coagulation bath temperature, and its effect on the resulting fiber. Multiple authors have studied bath concentrations up to 70 wt% [2,3,6,[8][9][10][11]. Many of these authors were spinning at elevated bath temperatures (>20 °C).…”

Effect of Bath Concentration on Coagulation Kinetics at the Early Stage during Wet Spinning of PAN Copolymer Nascent Fibers

“…[3][4][5][6][7][8][9][10][11][12] The influence of coagulation conditions on the coagulation process during the wet spinning of PAN nascent fibers have also been reported. [13][14][15][16] However, the mechanisms of the coagulation during wet spinning are not yet well understood.…”

Investigation the jet stretch in PAN fiber dry‐jet wet spinning for PAN‐DMSO‐H2O system

“…[1][2][3][4] Polyacrylonitrile (PAN) fibers are the most widely used precursors for producing carbon fibers, owing to a variety of reasons. [5][6][7][8][9] Generally, optimum PAN precursors have many features, such as homogeneous structure, fine denier, high crystallinity, high orientation, and so on. Such fibers are either wet spun or dry-jet wet spun using dimethyl sulfoxide (DMSO)-water solution as a coagulation bath.…”