Melt spinning of continuous fibers by cold air attenuation I: experimental studies

Traditionally ultrafine continuous fibers below 1 dpf are produced by extrusion followed by mechanical drawing. In this study, a modified melt spinning apparatus with a high-speed air nozzle was designed and fabricated to produce continuous polypropylene (PP) fibers by cold air drawing only. With this setup, the fiber is quenched and simultaneously attenuated by a symmetric cold air jet. Since the formation of the fiber structure is highly dependent on the processing conditions, the new process provides a unique operation window to study fiber attenuation and structural formation under high-speed cold air drawing. A parametric study was carried out under different process conditions which included processing temperature, air velocity and polymer volume flow rate. Effects of changes in processing variables on the fiber diameter, molecular orientation, tensile strength and other properties were studied. Findings from this study could lead to new processing technologies for producing innovative fiber products.