TIME-RESOLVED IN-SITU X-RAY-SCATTERING STUDIES OF AQUEOUS HYDROXYPROPYLCELLULOSE SOLUTIONS

The evolution of the global orientation parameter for a series of aque ous hydroxypropylcellulose solutions both during and following the ces sation of a steady-state shear Bow is reported. Time-resolved orientat ion measurements were made in situ through a novel X-ray rheometer cou pled with a two-dimensional electronic X-ray camera, and using an inte nse X-ray source at the LURE synchrotron. After the cessation of flow, the global orientation decreases from the steady state orientation le vel to zero following shear flow at a low shear rate or to a small but finite value after flow at a high shear rate. The decrease of orienta tion with time shows different behaviour, dependent upon the previousl y applied shear rate.