4. Spinning from concentrated polymer solutions

This type of process, also known as collodion spinning or dope spinning, is mainly used, as we have already seen :

• on the one hand, multifilaments based on polyacrylonitrile, a polymer whose basic unit has the structural formula: $—{\mathrm{CH}}_{\mathrm{2}}—\mathrm{CH}—\left(\mathrm{C}\begin{array}{c}\\ \\ \end{array}\mathrm{N}\right)$ (so-called acrylic fibers);

• on the other hand, regenerated cellulose multifilaments, the archetype of which is rayon (or rayon-viscose), still used, albeit less and less,...