Silica-Filled Polyacrylonitrile Solutions: Rheology, Morphology, Coagulation, and Fiber Spinning

Abstract

The fumed silica influence on the morphology, coagulation processes, and rheological properties of suspensions in dimethyl sulfoxide (DMSO) and polyacrylonitrile (PAN)–DMSO solutions has been studied for the production of composite films and fibers. It has been shown that silica–DMSO concentrated suspensions (24 wt%) form a weak gel with a yield point of about 200 Pa. At concentrations of ~5 wt% and above the dispersions, depending on the shear stress, are pseudoplastic or dilatant liquids. It has been found that the silica addition method into a PAN solution has a significant impact on the aggregates dispersibility and the rheological behavior of the obtained systems. A thixotropy appearance and a sharp increase in the relaxation time were observed for PAN solutions at a SiO2 content of more than 3−5 wt%, which indicates the formation of structures with a gel-like rheological behavior. Upon reaching the critical stress their destruction takes place and the system starts to behave like a viscoelastic liquid. Two spinning methods have been used for preparing fibers: standard wet and mechanotropic. By the mechanotropic method it is possible to achieve a higher draw ratio at spinning and to obtain fibers with better mechanical properties. It is possible to spin fibers from PAN solutions containing up to 15 wt% of silica per polymer with a tensile strength up to 600 MPa.

Electrospun Silica-Polyacrylonitrile Nanohybrids for Water Treatments

“…On the other hand, Ullah et al also reported good mechanical and thermal properties of PAN nanofibers, but the tensile strength decreased with the addition of silver sulfadiazine in PAN nanofibers during electrospinning [ 52 ]. When testing the strength of PAN fibers using a mechanotropic method, Varfolomeeva et al reported high-strength PAN fibers, but the addition of silica led to a decrease in fiber strength [ 53 ]. The addition of inorganic particles into a polymer matrix can improve the mechanical property of the membrane.…”

Polyacrylonitrile Fibers with a Gradient Silica Distribution as Precursors of Carbon-Silicon-Carbide Fibers

“…PAN solutions with TEOS additions were prepared at 70 • C on a laboratory opposing mixer [22], which allows homogenizing concentrated polymer solutions, protecting them from ingress of air and moisture from the outside.…”

“…SiO 2 is used as a silicon-containing modifier component, and composite fibers obtained by electrospinning [7,14,[18][19][20][21], often, simultaneously with achieving the required special characteristics demonstrate inhomogeneous morphology due to the formation of large aggregates [7,8,12,14,20], that could decrease mechanical properties [12,22].…”