Effect of coagulation conditions on solvent diffusions and the structures and tensile properties of solution spun polyacrylonitrile fibers

Abstract

Polyacrylonitrile (PAN) fibers were spun by solution spinning. In this work, two coagulation compositions, dimethyl sulfoxide (DMSO)/water and methanol, were used, and coagulation temperatures were varied from −20 to 0 to 20 °C. The coagulation compositions and temperatures strongly affected the solvent diffusion processes, the structures of as‐spun fibers, and the tensile properties of final drawn fibers. When DMSO/water was used as coagulation bath, non‐solvent (water) diffused into PAN fibers and led to a quick PAN solidification. By comparison, when methanol was used as coagulation bath, no or minimal amount of methanol diffused inward to the fibers. The different solvent diffusion behaviors in DMSO/water and methanol baths led to different structures of as‐spun PAN fibers. It was observed that the tensile properties of final drawn fibers strongly depended on the coagulation conditions. When methanol was used as coagulation bath and the bath temperature was −20 °C, PAN fibers was found to possess the best tensile properties, a tensile strength of 0.89 GPa and young modulus of 20.4 GPa. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 44390.

A comparison of coagulation and gelation on the structures and stabilization behaviors of polyacrylonitrile fibers

“…The quick solidification of PAN dope leads to the formation of a solid and hard sheath when spinning dope passes the coagulation bath, which would further collapse and form kidney‐shaped cross section as shown in Figure (a). By comparison, methanol was used as gelation bath component in dry‐jet gel spinning, and our previous studies have proven that the solidification of PAN dope is minimized inside low‐temperature gelation bath and a round cross section would be formed …”

“…PAN/DMSO solution with a weight fraction of 20% was prepared according to a reported dissolution procedure . The PAN solution (dope temperature 50~60 °C) was spun using a stainless steel syringe equipped a 1.27 cm long blunt tip (hole diameter 510 μm) and self‐made high pressure injection pump, which was the same spinning equipment in our previous studies . A thin layer of air gap (12 mm) was used.…”

“…Nowadays, it is widely recognized that the mechanical properties of carbon fibers are determined by the quality and structures of raw PAN fibers . The physical structures of PAN fibers are developed during fiber spinning, and many researches have been carried out . Since 1970s, (dry‐jet) wet spinning methods have been widely adopted by carbon fiber manufacturers.…”

Structural changes of polyacrylonitrile fibers in the process of wet spinning

“…Every stage of wet spinning is important for achieving homogenous PFs. In contrast to the comprehensive studies on the structural characteristics of PAN‐based PFs, only limited reports were made on its formation process . James et al .…”

Effects of the coagulation temperature on the properties of wet‐spun poly(vinyl alcohol)–graphene oxide fibers

“…Many recent studies have also shown that fibers produced by gel spinning at low temperature and thermal stretching at high temperature always presents excellent mechanical properties because most of the holes inside the fiber could be removed to form dense fibers . Hao et al . investigated the effects of the coagulation temperature and its components on solvent diffusions on the structures and tensile properties of solution‐spun PAN fibers.…”