Compression of anisometric granular materials

Granular particles of anisometric shape are common in many technologies and the knowledge of their compression response is needed for their handling, storage, transport and flow. Despite its importance, a little attention has been paid to this problem so far. Therefore, our contribution is an experimental study focused on the uniaxial compression of random layers of dry anisometric (prolonged) particles of various kinds with a broad spectrum of properties. Eight different materials were tested, both organic and inorganic, both regular model-shaped and irregular real-shaped (hollow plastic beads, graphite rods, rod-like pasta, hair-like pasta, glass fibres, crystals of: terephthalic acid, KMnO4, PbCl2). Compressibility curves were measured using the tablet press Gamlen GTP-1 (our working range 0–9 MPa). The data were fitted with four compression models (Kawakita, Heckel, Shapiro, Adams). All these models worked satisfactorily well within the range of their validity. The results show that the powder-compaction models, originally suggested for fine general powders, can be applied also to coarse anisometric particles. Different granular materials were compared by their location in the model parameter planes, and the difference between anisometric particles and general powders was highlighted.