Blending of agglomerates into powders 1: Quantification of abrasion rate

A very common situation in the pharmaceutical arena is that a small amount of cohesive drug substance needs to be distributed in a large bulk of free-flowing filler such as lactose. The key topic of attention is that aggregates of a cohesive drug substance need to be sufficiently broken up in an acceptable time-frame. This implies that there is need for a better mechanistic understanding of the blending process and the reduction in size of the aggregates. The purpose of this study is to obtain more insight in the mechanisms that lead to the break up of assemblies of powder particles in a moving powder bed. The break up of aggregates was studied by application of so-called brittle Calibrated Test Particles (bCTPs). These are well-defined aggregates with brittle fracture properties. The dominant mechanism of the break up of these aggregates is abrasion by multiple impacts. There is evidence of a relationship between strength (expressed as porosity) of the bCTPs and rate of abrasion. This is often a slow process and the rate is determined not only by the (mechanical) properties of the agglomerates and process conditions, but also by the particle size distribution of the bulk filler.