AN ASSESSMENT OF SUBSTRATE-BINDER INTERACTIONS IN MODEL GRANULE SYSTEMS .2. SCANNING ELECTRON-MICROSCOPY

Previous publications have demonstrated the importance of surface ener getic interactions between materials during wet granulation processes. In this paper the influence of such interactions on the morphology an d structure of the dry granular product is considered. Initially two m odel powders and two typical solution binding agents were selected and characterised to define their particulate and energetic properties. T he surface energetic interactions of these materials were then predict ed from these properties using a method first developed for estimating interactions in molten polymer blends. Considerable differences were noted in the wetting, spreading and adhesion tendencies of the various substrate-binder combinations. The structural and morphological prope rties of dry granules produced from the model materials using a contro lled wet granulation process were then assessed using scanning electro n microscopy. In each system studied the properties of the dry granula r product were markedly affected by the substrate-binder energetic int eractions occurring during wet granulation, and these effects could be accurately predicted from the surface energetic properties of the raw materials.