COAGULATION RATE STUDIES OF SPINNABLE CHITOSAN SOLUTIONS

The coagulation properties of some mixtures of 5% chitosan in 2% aqueo us acetic acid were investigated with the goal of determining the opti mal coagulation conditions for the spinning of chitosan fibers. The ch itosan was characterized and found to possess a deacetylation value of 84.9 +/- 0.2%. Molecular weight of the chitosan was also measured; ba sed on intrinsic viscosity, the M-V value was 7.73 x 10(5) g mol(-1), and based on high-pressure liquid chromatography, the M-w value was 1. 14 x 10(5) g mol(-1). Solutions of 5% chitosan/2% acetic acid were pre pared, filtered, and extruded through a large-diameter hole syringe in to coagulation baths of varying composition that were all strongly bas ic in nature, at least a pH of 12 or greater. For each coagulant, time was varied from between 22 s and 2 minutes at room temperature. A sec ond set of experiments was conducted where the temperature was varied from 20 degrees C to 70 degrees C at a constant time of 45 s. In a thi rd set of experiments, using a 1M NaOH coagulant, different chitosans were also analyzed. Throughout all of the experiments, a distinct movi ng boundary between coagulated and uncoagulated polymer was observed w ithin the cylindrical-shaped polymer fibers. Using a series of equatio ns based on Fick's 2nd Law, a straight line relationship has been demo nstrated between boundary motion and time and between boundary motion and temperature for each coagulant tested. The activation energy for e ach coagulant was also determined. (C) 1997 John Wiley & Sons, Inc.