Solution Spinning of PLLA

FIGURE 20.8 A schematic depiction of supramolecular fibrillar morphology in PLA fibers (adapted from Ref. 24 with permission from John Wiley Sons, Inc.). 

The spinneret plate used in solution spinning is made of a soft corrosion resistant material, such as special grade stainless steel or platinum. It is usually thin with the diameter of individual spinneret holes in the range of0.025-0.05 mm and l/d ratio of 1. Both the diameter and length of the spinneret are much smaller than those used for melt spinning. This is because the viscosity of the polymer solution is significantly lower (3000-7000 cP) and a high back pressure is not 

Temperature is another important parameter in wet spinning. The temperatures of the extmded fluid and of the coagulation bath are controlled separately. Usually, the dope temperature is kept higher to avoid fluid flow problems, while the coagulation bath temperature is kept lower to control the coagulation rate and improve the cohesiveness of the spinning line. 

---