Formation of hollow granules from liquid marbles: small scale experiments

Research into formation of hollow granules from liquid marbles is an emerging field in hydrophobic granulation. A liquid marble is formed by a network of self-assembled hydrophobic powder around a droplet, and this paper investigates the conditions required for forming hollow granules from a liquid marble precursor. Single drops of fluid were produced using a syringe and placed onto loosely packed powder beds of hydrophobic powders. Liquid marbles formed from several powder/liquid combinations were dried at several conditions to investigate the drying conditions required for formation of a stable hollow granule. The formation of stable hollow granules was found to depend on drying temperature and binder concentration. For HPMC and PVP binder, formation of hollow granule is proportional to binder viscosity and for HPC binder, this relationship is constant. Different combinations of powder and binder at both drying temperatures - 60 °C and 100 °C - had mixed success rates in forming hollow granules, but generally the success rate was improved by using higher drying temperatures, smaller particles or higher viscosity binder fluids. © 2009 Elsevier B.V. All rights reserved.