Characterisation of flowability of cohesive powders by testing small quantities of weak compacts

摘要

Characterisation of flowability of small quantities of cohesive powders is of great industrial interest, particularly for the pharmaceutical sec- tors, where a limited amount of material is available or the material is not easily accessible. In this paper, ball indentation on a powder bed is evaluated for flow characterisation of small quantities of cohesive powders at low levels of consolidation pressures. In parallel, the bulk powder is subjected to the common test method of unconfined direct compression. Analogous to indentation hardness testing, for which the indentation pressure is related to the flow stress, a constraint factor (C) is defined relating the unconfined yield stress and indentation pres- sure. The constraint factors for the test powders have been evaluated, enabling an easy method to characterize the flow behaviour of cohesive powders.