AbstractA study is carried out to investigate the effects of spinning conditions on fiber formation in the wet‐spinning process. The spinning conditions studied are free velocity (and hence free diameter), throughput rate, maximum take‐up velocity, jet stretch (the ratio of take‐up velocity to free velocity), and filament tension. The coagulating bath temperature and concentration are varied, and three spinnerette diameters are used. The spinning dope is an aqueous solution of polyacrylonitrile in sodium thiocyanate. The present study shows that the coagulating bath concentration influences the spinning tension and maximum take‐up velocity. Two thread breakage mechanisms are postulated which take into account the rate of coagulation, spinning tension, and thread velocity. An attempt is made to predict the concentration profile of solvent in the moving filament by simultaneously solving the mass and force balance equations, in which the increase in elongational viscosity along the spinning way is assumed to be mainly due to the hardening
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