The Development of a Rotary-intrusion-type Rheometer for a Powder Bed and the Measurement of the Dynamic Physical Properties of Powders

A rotary type of rheometer with a conical rotor has been applied to measure the flow characteristics of powders. The shearing torque as a function of the boundary area in the friction zone of the rotor was continuously measured during intrusion of the conical rotor into the powder bed. The effects of the rotor shape and operating conditions on the torque variation curves were investigated, and an empirical coefficient C including factors of stress and internal friction coefficient was proposed to express the change in the physical properties of the powders. The applicability of this testing method was confirmed by measuring two typical powder samples: a binary-component mixture of fine powders processed under different operating conditions, and polymer particles coated with different kinds of wax.