Rheological properties of chitin/lithium chloride, N,N-dimethyl acetamide solutions

Rheological properties of 1, 2 and 3 wt% chitin/lithium chloride (LiCl), N,N-dimethyl acetamide (DMAc) (one part of LiCl in 20 parts of DMAc by mass) solutions were investigated using an advanced rheometric expansion system for the purpose of improving the properties of chitin fibre. The results from steady rheological testing showed that the 1, 2 and 3 wt% chitin/LiCl,DMAc solutions were non-Newtonian fluids with shear-thinning behaviour. The 2 wt% chitin/LiCl,DMAc solution formed lyotropic liquid crystals, as determined from the decreased apparent viscosity in contrast to the 1 wt% chitin/LiCl,DMAc common solution. The results also implied that the 2 wt% chitin/LiCl,DMAc liquid crystals should have best spinnability and give best quality of fibre after spinning among the three solutions. The 3 wt% chitin/LiCl,DMAc solution had a similar appearance to the 2 wt% chitin/LiCl,DMAc liquid crystals. Dynamic measurements on the 3 wt% chitin/LiCl,DMAc solution showed that the changes in its viscous and elastic properties with temperature were different from common polymer solutions, in that the first normal stress difference could be negative and higher temperature could give higher viscosity. These findings suggested the existence of liquid crystals in the 3 wt% chitin/LiCl,DMAc solution.