2006 Volume 34 Issue 1 Pages 9-15
We have investigated structural rearrangement of an aqueous solution of hydroxypropylecellose (HPC) caused in a transient Couette flow between two parallel plates. After a pre-shear flow, a subsequent flow starts with a different direction. The flow induced structural changes were examined with the SALS (Small Angle Light Scattering) method and measurements of the dichroism and orientation angle. We have tested 9 patterns of flow direction change from acute to obtuse angle. After several strains in the subsequent flow, a streak obtained in the SALS method became clear and sharp, and then its direction was gradually turned to the final one. A corresponding peak and gradual change of the dichroism was obtained. A periodic isotropic scattering light was simultaneously observed in the SALS experiment and the damping oscillation in orientation angle was also measured. It is considered that the former shows the rearrangement of the flow structure includes a collapse and reconstruction of a macro structure and the latter means the synchronized tumbling motion was generated in this procedure.
