A new approach to coagulation phenomena in wet‐spinning

Abstract A new physicochemical model was built to describe the phenomena occurring during wet‐spinning of polyacrylonitrile, in order to relate the integral time of coagulation to the major variables of the spinning bath. According to this model, counterdiffusion of solvent and coagulant leads the system to overcome the thermodynamic equilibrium conditions, so that precipitation of polymer occurs, at a distance from the fiber axis variable with time. This causes a moving‐interface dope‐coagulated polymer to build up. The integral time required by this interface to reach the fiber axis, i.e., the coagulation time, is related, by simple equations to initial radius, to temperature via diffusional coefficients, to “bath hardness” (i.e., coagulant content), and to thermodynamic phase equilibrium conditions.