Properties of solutions of the copolymer of acrylonitrile with vinylimidazole and fabrication of a fibre from it

Abstract

When chemically active vinylimidazole is incorporated in the macromolecular polyacrylonitrile chain, an anomalous deviation of the viscosity from Newtonian flow is observed with an increase in the shearThe fundamental conditions for synthesis of the copolymer of acrylonitrile (AN) and vinylimidazole (VIM) for fabrication of fibres with chemisorption properties with respect to platinum-group metals, whose extraction is extremely important for the national economy, were previously established in [1].Incorporation of bulky molecules of VIM in the macromolecular polyacrylonitrile chain affects the properties of solutions of the copolymer, which in turn affects the physicomechanical indexes of the fibre [2]. We attempted to evaluate the properties of concentrated solutions of the copolymer as a function of the ratio of its components and to determine the effect of the conditions of spinning the fibre on its characteristics in use.AN--VIM copolymer with a concentration of VIM of under 40 wt. % and intrinsic viscosity [17] of 1.25-2.30 dl/g was investigated. The intrinsic viscosity of solutions of the copolymer in dimethyt sulfoxide (DMSO) was determined on a Ubbelohde viscometer. The rheological properties of the concentrated solutions were investigated on a VPN-0.1 constant shear stress viscometer. The composition of the AN-VIM copolymer was determined based on the concentration of saponified nitrogen [3]. The fibre was spun on a laboratory microbench with solution feed of 0.794 errra/min and a rate of 3.14 m/min using a spinneret with 40 openings 0.08 mm in diameter. In measuring the maximum rate of separating the fibre from the spinning bath, a spinneret with one opening 0.1 mm in diameter was used. A three-dimensional chemical network was formed in the fibre during thermal drawing using ED-20 epoxy--bisphenol A oligomer added to the spinning solution.The data on the flow of equiviscous solutions with a different concentration of chemically active monomer in the chain in reduced coordinates (Fig. 1, curves 1 and 3) were compared to determine the effect of the composition of the copolymer on the rheological properties of its solutions. The ratio of the effective r/e f tO the initial ~70 viscosity and the product of the shear rate gradient ~ and 7/0 were used as variables. For comparison, the curve of flow of a more viscous solution of the copolymer containing 33.3% VIM (curve 2) is also shown in Fig. 1. When the concentration of VIM in the copolymer is decreased to 11.5 % (curve 2), the deviation of the mode of flow of the solution from Newtonian appears for lower values of ~r/0. Index n in the following equation was used for evaluating the anomalous deviations of flow of the solutions of copolymer I~ = nlgr + lgk. where ~-is the shear stress; and k is a constant characterizing the effective viscosity of solutions of the polymer.All-Russian Scientific-Research Institute of Polymer Fibres, Mytishchi.

Poly (acrylonitrile – co -1-vinylimidazole): A new melt processable carbon fiber precursor

“…The objective of our study is to synthesize melt processable carbon fiber precursors which have the capability of thermal stabilization in air which would make them cost-effective and widen their applications. AN/VIM copolymers [33,34] have been reported by several researchers, but to the best of our knowledge none of AN/VIM copolymer compositions has been reported for carbon fiber applications. VIM comonomer can disrupt PAN crystallinity to make it melt-processable, while the unsaturated pendant imidazole groups enable the precursor to be thermally cross-linkable.…”

Plasticization for melt viscosity reduction of melt processable carbon fiber precursor

“…Poly(acrylonitrile-co-1-vinylimidazole) (AN/VIM) copolymers [25,26] have been reported by several researchers, especially of recent publications by Deng, et. al., where they reported the possibility of these copolymers could be used as precursors for carbon fibers without using UV treatment [28].…”