Relationship between mechanical properties and shape descriptors of granules obtained by fluidized bed wet granulation

This paper focuses on two mechanical properties of granules, the coefficient of restitution and the strength, and analyzes their sensitivity to granule geometric parameters. The granules were obtained by fluid bed granulation of glass beads with an aqueous solution of PEG1500. Collisions were arranged between granules, and for granules against two glass plates, the first of them a non-covered plate, whereas the second was a plate covered with a thin film of PEG1500. The coefficient of restitution and the strength were measured for the granules, the former for individual particles also. In the case of individual glass particles the coefficient of restitution was around 0.61 for impacts on the flat glass, and 0.5 on the covered glass; for the granules, this parameter was around 0.44 for both situations and for collisions between granules. Sphericity, lacunarity and fractal dimension of the granule projected area, as well as the granule porosity, were determined. Granules giving the highest values for strength had the largest fractal dimension and the smallest lacunarity values regardless of their sphericity, porosity and coefficient of restitution.