Polyacrylonitrile (PAN) fibres of high porosity and hygroscopicity .1. Pan fibres formed from solutions in dimethylformamide (DMF)

The conditions of forming highly porous and hygroscopic PAN fibres from an acrylonitrile/methyl methacrylate copolymer (96.45 mass-% acrylonitrile) were established. Fibres were formed from a DMF solution upon introducing into a water-DMF coagulating bath. Optimum drawing ratio from the spinning nozzle and temperature and composition of the coagulating bath were determined. Under such conditions the resulting fibres had a differentiated shell-core structure, an internal surface area of about 97 cm(2)/g and a total volume of pores 1.22 cm(3)/g. They revealed water sorption at 100% relative humidity and water retention, respectively, 14 and 12 times as high as those of conventional PAN fibres, with mechanical strength properties preserved at the level required for the textile-grade PAN fibres.