If the
melting point of the polymer is higher than its degradation temperature, the polymer must undergo solution spinning techniques for fiber formation. The polymer is first dissolved in a
solvent, forming a spinning
solution (sometimes called a "
dope"). The spinning solution then undergoes dry, wet, dry-jet wet, gel, or electrospinning techniques.
Dry spinning A spinning solution consisting of polymer and a volatile solvent is extruded through a spinneret into an evaporating chamber. A stream of hot air impinges on the jets of spinning solution emerging from the spinneret, evaporating the solvent, and solidifying the filaments. Solution blow spinning is a similar technique where polymer solution is sprayed directly onto a target to produce a
nonwoven fiber mat.
Wet spinning Wet spinning is the oldest of the five processes. The polymer is dissolved in a spinning solvent where it is extruded out through a spinneret submerged in a coagulation bath composed of nonsolvents. The coagulation bath causes the polymer to
precipitate in fiber form.
Acrylic,
rayon,
aramid,
modacrylic, and
spandex are produced via this process. of fibers. The process does not require the use of coagulation chemistry or high temperatures to produce solid threads from solution. This makes the process particularly suited to the production of fibers using large and complex molecules.
Melt electrospinning is also practiced; this method ensures that no solvent can be carried over into the final product. ==Post-spin processes==