Melt spinning of polyamide 4

Polyamide 4 (PA 4), a biobased and biodegradable polymer, is firstly produced into fibers by melt spinning. PA 4 is a thermally‐sensitive polymer that is difficult to be processed by melting methods, while through mixing with an ionic liquid (IL)—1‐butyl‐3‐methylimidazolium chloride (BmimCl), the melting point of the PA 4 decreases 40°C when 30 wt% ILs are incorporated. Homogeneous and circular cross‐sectional PA 4 fibers are produced at winding speeds of 19, 79, 228 and 396 m/min. The as‐spun PA 4 fibers produced at 19 m/min winding speed can maximally be drawn four times in a water bath with temperatures ranging 60–75°C. The mechanical properties of the PA 4 fiber reach an optimum value as the fiber is drawn at 65°C. The ILs are fully removed when the fibers immerse in water for 3 min. In the meanwhile, the melting point of PA 4 is gradually enhanced with washing. Moreover, the crystallization of the washed PA 4 fibers increases, while the orientation of the crystals slightly decreases. The application of IL can be extended to improve the processibility of thermally‐sensitive polymers that cannot be directly manufactured by melt‐extrusion based technologies.