wetspinning

Wet spinning is a fiber fabrication process in which a polymer is dissolved to form a viscous dope and extruded through a spinneret into a coagulation bath containing a non-solvent. In the bath, solvent exchange with the non-solvent causes the polymer to precipitate as a continuous filament, which is then drawn to increase orientation and collected on a take-up device. The coagulation bath composition, temperature, and draw ratio influence the fiber’s diameter, strength, and other properties.

Typical steps include preparing and filtering the dope, removing trapped air, extruding through the spinneret, allowing coagulation in the bath, washing to remove residual solvent and by-products, drawing to align polymer chains, and finally drying and finishing. Some systems incorporate an air gap between the spinneret and the bath to adjust fiber morphology before coagulation.

Common polymers processed by wet spinning include regenerated celluloses such as viscose rayon and certain synthetic polymers that are difficult to melt or dry, such as polyacrylonitrile (PAN) and aramids (for example, Kevlar). Wet spinning is also used for specialty fibers and for carbon fiber precursors, where the technique enables control over filament structure and properties.

Advantages of wet spinning lie in its ability to process polymers with low or non-volatile solvents and to produce continuous filaments with good strength and uniformity. Challenges include the handling of solvents and non-solvents, energy and equipment requirements for bath regeneration and solvent recovery, and environmental and safety considerations associated with coagulation chemistry.