Hysteresis behaviors of poly (naphthalene quinone) radical electrorheological fluid

As a potential electrorheological(ER) material, poly(naphthalene quinone) r adical (PNQR) ER fluid was prepared, and its rheological behavior and hyste resis phenomenon were investigated. PNQR was synthesized by Friedel-Crafts acylation between naphthalene and phthalic anhydride, using zinc chloride a s a catalyst at 256 degrees C. A Physica rheometer equipped with a high vol tage generator was used to measure the rheological properties of the ER flu ids, which were prepared by dispersing PNQR in silicone oil at several part icle concentrations. Shear stresses were observed to decrease as shear rate increased in the region of slow deformation rate. It was further found tha t ER fluid showed different hysteresis behaviors according to the shear rat e ranges; thixotropy was observed in the low shear rate region (0.007 - 0.5 1/s) and anti-thixotropy in the high shear rate region (0.5 - 1000 1/s). C ontrolled shear stress mode was also applied to observe similar behaviors.