The use of surface energy values to predict optimum binder selection for granulations

Abstract

The surface energy of microcrystalline cellulose (Avicel PH101), was assessed using a Wilhelmy plate technique. Using values for the surface energy of binders that are available in the literature, it was possible to predict the spreading behaviour of binder over powder and vice versa. This was taken as a method by which the optimum binder for the powder might be selected. To test the prediction, granulations of microcrystalline cellulose were made using hydroxypropylmethylcellulose (HPMC), polyvinylpyrrolidone (PVP) and water as binding agents. The granulations were tested for friability, density, bulk density, tapped bulk density, angle of repose and size distribution. The variables that were considered were the binder used, the volume and concentration of binder solution, the particle size of the powder to be granulated and the quantity of powder to be granulated. The major conclusions were that the granulation was poor if a small quantity of powder was placed in the mixer, the particle size of the powder did not alter the size of the granules that were produced, but did alter the other properties (e.g. friability): an increase in concentration of the binder solution does not necessarily result in improved binder performance, but an increase in the volume of the binder solution produced a significant improvement in granule properties. The prediction of binder performance based on surface free energies and polarity proved reliable in that HPMC was superior to PVP as a binding agent for this powder.