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Keywords:

  • shear;
  • electrostatics;
  • charge density;
  • impedance;
  • dielectrophoresis;
  • powder flow;
  • composition

Abstract

This article examines the effects and interactions of shear rate, shear strain on electrical and flow properties of pharmaceutical blends. An unexpectedly strong relation between the 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 after they were subjected to a controlled shear environment. It was found that the increase in the shear strain intensified the electrical properties for blends that did not contain MgSt. The opposite effect was found in blends lubricated with MgSt. Different shear conditions resulted in different correlations between flow index and dilation. Flow properties of powders were found to improve with continuous exposure to shear strain. It was also found that flow properties correlated to charge acquisition and impedance for different shear treatments. © 2009 American Institute of Chemical Engineers AIChE J, 2010