(663b) Effects of Shear and Electrical Properties On Flow Characteristics of Pharmaceutical Blends
The effects and interactions of shear rate, shear strain and electrostatics on flow properties of pharmaceutical blends are examined in this work. An unexpectedly strong relation between flow and passive electrical properties of powders is observed to depend on the shear history of the powder bed. Charge density, impedance, dielectrophoresis, flow index and dilation were measured for several pharmaceutical blends. All powders were subjected to a controlled shear environment and their flow and electrical properties were measured. Relationships between blend composition on shear, electrostatics and powder flow were investigated by examining the effect of adding lubricants and other types of pharmaceutical excipients. It was found that the increase in the shear strain increased the electrostatic charge density, impedance and dielectrophoresis blends that did not contain MgSt. The opposite effect was found in blends lubricated with MgSt, where the electrical properties decreased with an increase in the shear rate and strain. The effect on electrical properties due to shear strain and shear rate was found to be more strongly dependent on the presence of lubricant than other excipients and ionic additives. Different shear conditions resulted in different families of correlations between flow index and dilation. Flow properties of powders were found to improve with the continuous exposure to shear strain. It was also found that the flow index and dilation correlate to charge acquisition and impedance for different shear treatments.