Mathematical Modelling of the Pneumatic Melt Spinning of Isotactic Polypropylene. Part III. Computations of the Process Dynamics

Computer simulation of the pneumatic melt spinning of isotactic polypropylene based on the mathematical model of the process is presented. Two dynamic zones of the air jet-filament interactions along the melt blowing axis are predicted - a zone with a drawing activity of the air jets with aligned filaments in this zone, and a passive zone with the bending and coiling of the filaments. The diameter of the fibres and structures of the nonwoven should depend on the die-to-collector distance, and the zone in which the collector is located. Ranges of this zones are discussed as dependent on the initial velocity of the air jets, the melt extrusion temperature, and the molecular weight of the polymer. Axial profiles of the polymer velocity, diameter and temperature of the filament, the tensile force, tensile stress, and rheological pressure along the melt blowing axis are presented for a process with the collector located within the air-drawing zone at a fixed take-up distance. The dynamic profiles indicate a narrow axial range of air-drawing next to the spinneret.