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Valery Kulichikhin

Institute of Petrochemical Synthesis-RAS, Russia

Title: Uniaxial extension of polymer solutions as the main rheological factor in fiber spinning procedure

Biography

Biography: Valery Kulichikhin

Abstract

Fiber spinning processes from polymer solutions are the most difficult for practical realization compared to the melt spinning. They involve necessity to know the shear rheology of solutions (flow through the spinneret channels), the phase state of the initial solutions and their transformation during contact with coagulation bath, the extension rheology in the air gap (dry-wet method) or in liquid medium (wet method), accompanying with transition from non-Newtonian liquid to the gel-like system and, finally, to the solid viscoelastic product. Nevertheless, such polymers as aramides, polyimides, PAN and its copolymers, cellulose and others cannot be processed in fibers from melts, and only spinning from solutions remains the unique way to obtain textile and technical yarns. This lecture is devoted to development of the specific devices allowing combining rheological, optical and structural tests and analysis of the obtained results at extension of solutions PAN in DMSO, aramides in DMAA and cellulose in N-methylmorpholine-N-oxide. In addition, the role of such nanofillers as carbon nanotubes and clay in dopes was considered. The traditional way of removing a solvent from extended solution jet is contact with precipitator in coagulation bath. Due to an interdiffusion, the solvent is going away from the jet and non-solvent is coming into jet resulting in as-spun fiber formation. We have shown that at strong extension the phase transition in solution jet takes place and solvent passed away on periphery of jet/fiber. Calculations based on elaborated models for dilute and concentrated solutions have shown that less than 0.1% of solvent remains in resulting fibers. This process was realized in laboratory spinning stand and prepared fibers were investigated by different methods. The skin-core effect is missed for such fibers with diameter of 5-10 m and their structure is closed to oriented para-crystalline phase. Mechanical characteristics of such fibers are higher than of fibers obtained by traditional methods, and behavior at thermolysis at carbonization is very promising.