Instead of the traditional wet spinning approach of producing fibers from chitosan, a pseudo-dry spinning approach was used by Notin et al. Deacetylated chitosan (degree of acetylation, 2.7 %) with molecular weight of 540,000 g/mol was dissolved using aqueous acetic acid solution. After extrusion, the fibers were exposed to gaseous ammonia rather than coagulating the fibers for precipitation. Upon exposure to ammonia, ammonium acetate was produced that could be easily eliminated. This approach of pseudo-dry spinning did not result in severe damage to the molecular weight of chitosan even after storing the fibers for 2 months. SEM images showed that the chitosan was completely coagulated, and the fibers obtained had a smooth and regular surface. Fibers produced had tenacity between 0.9 and 5 g/den, elongation between 4 and 9 %, and modulus between 238 and 531 g/den [06Not1, 06Not2]. Further studies by the authors showed that post-drying of the fibers for 1 week under ambient atmosphere was necessary to stabilize the fibers [06Not1, 06Not2]. Optimizing the jet-stretch ratio during coagulation and the post­drying of the fibers lead to the production of fibers with a tenacity of 2 g/den and a modulus of 82 g/den. Aging of fibers under ambient condition was reported to assist the formation of anhydrous crystalline form with fibers containing large amounts of tendon forms and lesser amounts of annealed/anhydrous form. X-ray studies showed that the crystallinity index increased with aging time from 15 to 24 % after 5 months of aging. Morphologically, the fibers obtained had a fibrillated surface with an average fibril diameter of 140 ± 50 nm and between 100 and 175 nanofibrils/4 pm2 as seen in Fig. 25.1a, b. Although the fibers produced with this method had better tensile properties compared to fibers produced from other methods, it should be noted that the wet stability of the fibers was not reported. Chitosan fibers are inherently weak when wet and need to be cross-linked or chemically modified to improve stability in aqueous environments [06Not2].