External Coagulant in Fiber Preparation

External coagulant is a non-solvent liquid or a mixture of solvent/non-solvent in a collecting bath (coagulation bath) used for fabrication of fibers by the dry-/wet-spinning technique or the wet-spinning technique. Coagulation of the external surface of the nascent fiber can start immediately after its extrusion from the spinneret (wet spinning) or after the as-spun fiber crosses an air gap (i.e., distance between the spinneret and the coagulation bath) through which the external surface experiences coalescence and orientation of polymer aggregates (wet/dry spinning). In general, the nascent fiber is partially coagulated by the internal coagulant (bore liquid) and/or through the air gap by solvent evaporation, and finally the coagulation is completed in the coagulation bath by an external coagulant.

The type of the external coagulant affects considerably the structural morphology of the resulted fiber. Usually, water is the preferred external coagulant because of its low cost and...