Evaluation of three non-linear packing density models on micropowder mixtures

Abstract

The formulation of powders often requires an optimized packing density of the granular skeleton which takes into account the desired properties. More accurate than the conventional linear models, three non-linear packing density models are evaluated from published data on binary or ternary mixtures of alumina powders, glass microbeads, siliceous microaggregates: the Compressible Packing Model (CPM), the 3-parameter Particle Packing Model (3PPM), the Theoretical Packing Density Model (TPDM). Depending on the models, they involve a compaction index K and certain particle interactions: the loosening effect a and possibly the critical cavity size ratio x0 from which it appears, the wall effect b and the wedging effect c. The CPM (with a, b, K), by incorporating only 2 interaction functions for a and b, reduces its versatility but is efficient for siliceous. The 3PPM (with a, b, c), by incorporating 9 interaction functions, adapts well to the various micropowders with however a lower performance for the siliceous for which the packing densities predicted in “compacted” conditions are lower than in “uncompacted” conditions. The TPDM (with a, b, K, x0) is effective for all types of micropowders and generates the best statistical indicators.