Regenerated protein fibers. II. Viscoelastic behavior of silk fibroin solutions

The dynamic viscoelastic behavior of a concentratedsolution of silk fibroindissolved in the MU solvent is measured. The dynamic viscosity η' and dynamic elasticity G' increase with increasing concentrationof silk fibroinat constant frequency; however, the increasing frequency decreases η' and G' at a constant concentrationof silk fibroin. When the mixing ratio of C 2 H 5 OH/H 2 O in the MU solvent is increased at a constant concentrationof LiBr.H 2 O, η' and G' sharply increase at constant frequency. If the LiBr. H 2 O concentrationis varied in the MU solvents whose ratio of C 2 H 5 OH/H 2 O is kept constant at 100: 0, both η' and G' are greater for LiBr.H 2 O concentrationsof 50% by weight compared to concentrationsof 40% by weight. The dependence of η' on the temperature of the solution can be predicted by Andrade's viscosity equation. Spinnability improves when the SF concentrationis increased.