Solution spinning
Also searched as: wet spinning, dry spinning, dry-jet wet spinning, air-gap spinning, dope, spinning dope, coagulation bath
Solution spinning makes fibers from polymers that cannot be melted without degrading, by dissolving them into a viscous dope, extruding it and removing the solvent by evaporation or coagulation.
In detail
There are three main variants. In wet spinning the spinneret sits in a coagulation bath of nonsolvent, where the polymer precipitates as filaments; acrylic, modacrylic, viscose rayon and some aramids are made this way. In dry spinning the dope is extruded into a heated, gas-filled chamber and the solvent evaporates; cellulose acetate is traditionally dry spun from acetone, and spandex is generally dry spun. In dry-jet wet (air-gap) spinning the jets cross a short air gap before entering the bath, so they can be stretched while still fluid; para-aramid and lyocell are made this way.
The science and numbers
In wet spinning, solvent diffuses out while nonsolvent diffuses in, so a skin forms before the core solidifies; this diffusion balance controls voids and cross-section. Dry spinning is limited by evaporation rate and requires solvent recovery. Dry-jet wet spinning separates spinneret and bath by an air gap, typically about 0.1 to 10 cm in aramid patents, and stretching in the gap orients the molecules. Para-aramid dope in concentrated sulfuric acid is liquid crystalline: rodlike chains align into a nematic phase, and viscosity can fall as concentration rises. Lyocell dissolves cellulose in N-methylmorpholine N-oxide and water, and solvent recovery above 99 percent is reported for the process.
A practical example
A student compares fiber cross-sections under a microscope. Regular viscose shows a serrated outline, formed as its skin set first in the bath; dry-spun acetate shows a lobed outline; air-gap-spun lyocell is close to round. Each shape records how quickly, and from which direction, solvent left the forming filament.
What to distinguish
Solution spinning names a family of processes, not a fiber. The solvent, its hazards and its recovery rate shape much of the environmental profile, and they vary widely: amine oxide for lyocell, acetone for acetate, amide solvents such as dimethylacetamide for spandex, concentrated sulfuric acid for para-aramid. Do not confuse it with solution dyeing, which adds pigment to the dope.
Origins and history
Solution spinning predates melt spinning: the first artificial silks of the late nineteenth century were extruded from cellulose solutions. A key later advance came at DuPont, where Stephanie Kwolek found in 1965 that a para-aramid formed an unusual cloudy, liquid-crystalline solution, and Herbert Blades developed the dry-jet wet process that spun such dopes into high-modulus fiber. Lyocell later applied the air-gap method to cellulose dissolved directly in an organic solvent.
Related terms
Sources & further reading
- US EPA AP-42 Section 6.9: Synthetic fibers
- Polymers (PMC): Effect of high molecular weight PPTA on liquid crystalline phase and spinning process of aramid fibers
- Google Patents: US5393477A, Air gap spinning process for aramids
- ACS Omega: Optimization of dry-jet wet spinning of regenerated cellulose fibers
Technical references reviewed 2026-09-22. Examples are illustrative. Industry organizations and manufacturers describe their own fields; their references are not independent product endorsements. Figures are approximate and depend on the stated test conditions.