In the course of the development of fibers for artificial hair, we found that the polyamide 6 (PA 6) based blend fibers with granular rough surface can be prepared through the melt spinning of PA 6/Poly (ethylene terephthalate) (PET) blend polymer under particular spinning conditions. The surface roughness was found to be enhanced with the decrease of extrusion temperature and the increase of PET composition. Observation of the surface and cross-section of fibers after the acid-and alkali-treatment revealed that the rough-surface of the fiber was composed of the sea component of PA 6 whereas PET was dispersed evenly in the cross-section to form island component. Observation of the fibers captured from the spinning line revealed that the development of rough surface proceeded between the spinning nozzle and the water-quenching bath, in that the surface roughness was enhanced as distance from the spinning nozzle increased. It was difficult to clarify the fundamental mechanism for the development of rough surface even after analyzing the variations of the temperature of molten polymer and the size of the dispersed PET component in the extrusion system and the variation of the die-swell ratio depending on the extrusion conditions. It was speculated that further investigation is necessary from the view point of the crystallization behavior of PET in the process.

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