REGENERATED PROTEIN FIBERS .2. VISCOELASTIC BEHAVIOR OF SILK FIBROIN SOLUTIONS

The dynamic viscoelastic behavior of a concentrated solution of silk f ibroin dissolved in the ''MU'' solvent is measured. The dynamic viscos ity eta' and dynamic elasticity G' increase with increasing concentrat ion of silk fibroin at constant frequency; however, the increasing fre quency decreases eta' and G' at a constant concentration of silk fibro in. When the mixing ratio of C2H5OH/H2O in the ''MU'' solvent is incre ased at a constant concentration of LiBr . H2O, eta' and G' sharply in crease at constant frequency. If the LiBr . H2O concentration is varie d in the ''MU'' solvents whose ratio of C2H5OH/H2O is kept constant at 100:0, both eta' and G' are greater for LiBr . H2O concentrations of 50% by weight compared to concentrations of 40% by weight. The depende nce of eta' on the temperature of the solution can be predicted by And rade's viscosity equation. Spinnability improves when the SF concentra tion is increased. (C) 1997 John Wiley & Sons, Inc.