Coagulation rate studies of spinnable chitosan solutions

Abstract

The coagulation properties of some mixtures of 5% chitosan in 2% aqueous acetic acid were investigated with the goal of determining the optimal coagulation conditions for the spinning of chitosan fibers. The chitosan was characterized and found to possess a deacetylation value of 84.9 ± 0.2%. Molecular weight of the chitosan was also measured; based on intrinsic viscosity, the Mv value was 7.73 × 105 g mol−1, and based on high-pressure liquid chromatography, the Mw value was 1.14 × 105 g mol−1. Solutions of 5% chitosan/2% acetic acid were prepared, filtered, and extruded through a large-diameter hole syringe into coagulation baths of varying composition that were all strongly basic 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 second set of experiments was conducted where the temperature was varied from 20°C to 70°C at a constant time of 45 s. In a third set of experiments, using a 1M NaOH coagulant, different chitosans were also analyzed. Throughout all of the experiments, a distinct moving boundary between coagulated and uncoagulated polymer was observed within the cylindrical-shaped polymer fibers. Using a series of equations based on Fick's 2nd Law, a straight line relationship has been demonstrated between boundary motion and time and between boundary motion and temperature for each coagulant tested. The activation energy for each coagulant was also determined. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 117–127, 1997