Low to high shear rate powder rheology in a rotational rheometer

Characterization techniques are essential for understanding powders’ complex behavior. Among different devices, the Anton Paar Powder Rheometer (MCR-302) was used to characterize high-density polyethylene (HDPE). The powder has a 214 μm median diameter and is classified as free-flowing. The rheometer measures the torque required to rotate an impeller within the powder cell over a wide range of impeller rotation velocities from 0.6 rpm to 600 rpm. The steady-state torque dependence on the rotation velocities of the impeller follows a function (similar to shear thickening) as in the mu-I-rheology, reflecting that the torque is sensitive to inertial/viscous effects at higher rotation velocities (60 and 600 rpm) while quasi-static at lower rotation velocities (0.6 and 6 rpm). Our results indicate that the dry air fluidization at 600 rpm has a minimal effect on the steady-state torque.