Wet-spinning of regenerated silk fiber from aqueous silk fibroin solution: discussion of spinning parameters.

Regenerated silk fibroin (RSF) fibers were obtained by extruding a concentrated aqueous silk fibroin solution into an ammonium sulfate coagulation bath. A custom-made simplified industrial-type wet-spinning device with continuous mechanical postdraw was used. The effect of dope concentration, coagulation bath, extrusion rate, and postdraw treatment on the morphology of RSF fiber was examined. The results showed that although RSF fiber could be formed with dope concentration between 13 and 19% (w/w), the ones spun from 15% RSF solution showed the most regular morphology being dense and homogeneous in cross-section with a smooth surface and a uniform cylindrical shape. Though it had little effect on morphology, postdraw treatment especially under steam, significantly improved the mechanical properties of the RSF fibers.