Influence of guest and host particle sizes on dry coating effectiveness: When not to use high mixing intensity

Abstract

The effects of material stiffness, host and guest particle sizes, and mixing intensity on dry coating quality were investigated using a high-intensity vibrational mixer, using KCl, cornstarch, aluminum silicate and nano-sized silica. The coating quality deteriorated with larger guest particle size at high process intensity, and high material stiffness. Coarse guest particles detached from host particles above certain mixing intensity, indicating higher intensity is not recommended; e.g., the best coating quality for cornstarch was for medium-sized hosts below 30 Gs intensity. However, for nano-silica guests, higher processing intensity did not lead to their detachment, but decreased their agglomeration. Such behavior was explained using the energy-based stick/bounce model and two indices. The coating quality index (Kc), the ratio of total detachment energy to relative kinetic energy, assessed the guest particle attachment tendency. The deagglomeration index (Kd), the ratio of deagglomeration energy to relative kinetic energy, assessed the guest particle agglomeration tendency.