The purpose of this study was to investigate the effects of the different surface properties of powders on granular agglomeration in a high-shear mixer. Polyethylene glycol 6000 (PEG 6000) was used as the melting binder. Three different powders, with mean granule sizes of 75-150 mu m were used as the raw materials: calcium carbonate, calcium sulfate, and sodium carbonate. The wetting properties of the raw materials were measured with a contact angle instrument. The results indicate that the speed at which the droplets sink into the powder bed and the contact angle of binder droplets on the powder surface play important roles in determining the progress of the agglomeration process. Several types of agglomeration were found: a slurry state, heterogeneous nucleation, snowballing, and induction growth behavior. Heterogeneous dispersion leads to induction behavior and subsequent growth, but a homogeneous dispersion leads to little or no nucleation and growth of agglomerate size. (C) 2011 Elsevier B.V. All rights reserved.
