Development of a New Aqueous Solution Highly Sensitive to Flow Birefringence

An aqueous solution, highly sensitive to flow birefringence and showing Newtonian viscosity is developed from the standpoint of material design to make the flow measurement easier using the flow birefringence method. The highly sensitive solution to flow birefringence is obtained by dissolving Congo Red (CR), which has a large optical anisotropy, into the aqueous solution of polyvinyl alcohol (PVA) of the average degree of polymerization 500 and of the average degree of saponification 98.8%, which can be easily oriented under the action of shear rate. The birefringence and viscosity of PVA–CR aqueous solutions are measured for a range of shear rate from 0 to 2000 s -1 . The dispersion of flow birefringence with various wavelengths is also determined. The sensitivity of flow birefringence for shear rate is higher by one or two orders of magnitude than that in aqueous solutions employed by previous investigators. The relation between viscosity and shear rate in the solution is Newtonian.