Preparation and characterization of citrate-crosslinked chitosan fiber /|cWannasiri Worakitkanchanakul

Abstract

Chitosan with a degree of deacetylation of 94.41% and molecular weight of 4.25 X 105 was wet-spun through a 50-hole (0.1-mm diameter) spinneret using a solution of 7% (w/v) chitosan in 4% (v/v) aqueous acetic acid. A sodium hydroxide (NaOH) coagulating system gave higher values of knot strength and elongation at break than a calcium chloride saturated aqueous methanol system. However, the tensile strength of chitosan fibers from both systems was not considerably different. Crosslinked chitosan fibers were prepared by adding citric acid to either a chitosan dope or to the first coagulation bath using NaOH coagulating system. The addition of citric acid in both cases appeared to increase the tensile strength of the fiber, while knot strength was not improved. An increase in elongation at break was found, especially with the addition of citric acid to the spinning dope. Interestingly, SEM micrographs showed rough, instead of smooth, fiber surface for fibers produced using high citric acid content in both chitosan dope and the first coagulation bath. An additional experiment was performed whereby glutaraldehyde was used instead of citric acid in chitosan dope. The glutaraldehyde-crosslinked chitosan fiber obtained showed quite similar trends in mechanical properties as for the citrate crosslinked fibers except that the concentration range of applied glutaraldehyde was lower.