Melt spinning of continuous fibers by cold air attenuation: II. Theoretical modeling

A modified melt spinning apparatus with a high-speed air nozzle was designed and fabricated to produce continuous polypropylene fibers by cold air drawing only. The experimental studies based on this novel process were described in Part I of this paper series. In this succeeding paper, a one-dimensional non-isothermal Newtonian fluid model is formulated that can be used to analyze the fiber attenuation mechanisms. Unlike melt spinning, the position of the model geometry for the lower boundary is undetermined due to the unknown position of the fiber freezing point. In this model, a method of iteration on the initial model geometry was used to determine the fiber freezing point at which the fiber temperature reaches its freezing point and the velocity gradient equals zero. The results showed good agreement between simulated results and experimental data for the relationship between processing conditions and resulting fiber diameter.