Granule deformation and densification during compression of binary mixtures of granules

The purpose of this study was to investigate whether the deformation and de nsification during compression of one type of granules are affected by adja cent granules of a different porosity, corresponding to different mechanica l strength. Three mixtures were prepared, each consisting of two types of m icrocrystalline cellulose pellets (intermediate porosity study pellets plus low, intermediate or high porosity surrounding pellets) in the proportion 1:7. The mixtures were compressed and the study pellets were retrieved and analysed in terms of porosity, thickness, surface area and shape. It was sh own that the study pellets were compressed by deformation and densification . The degree of densification (decrease in porosity) of the study pellets w as independent of the porosity of the surrounding pellets but the deformabi lity (changes in the thickness, surface area and shape) of the study pellet s was linked with the porosity of the surrounding pellets. It is concluded that the mode of deformation of the study pellets was regulated by the poro sity of the surrounding granules; in a mixture containing granules with a l ow porosity, compression resulted in irregular study granules with regularl y positioned indentations caused by the surrounding granules. The compressi on properties of the surrounding granules affected the flattening of the st udy grannies to a lesser degree. (C) 2001 Elsevier Science B.V. All rights reserved.