The use of single particle mechanical properties for predicting the compressibility of pharmaceutical materials

Abstract

The study's primary goal was to examine the possible use of single particle mechanical properties to estimate the compressibility behaviour of a tablet's excipients during compaction. Nanoindentation was utilised to measure individual mechanical properties (Young's modulus, nanoindentation hardness, energy of elastic and plastic deformation). On the bulk scale, studied excipients' compressibility was determined by Heckel and Walker models. Single particle hardness was found to provide direct information regarding an excipient's plasticity since an excellent correlation was established with the Walker model on the bulk level. A moderate correlation was obtained with the Heckel model due to its lack of fit for brittle materials. The indentation energy on a single level effectively differentiates materials in which plastic deformation dominates from those materials in which brittle fractures prevail. Elastic properties of materials can be successfully predicted by measuring the energy of elastic deformation on a single scale since an excellent correlation was observed with the bulk parameters such as energy of elastic deformation and the tablets' elastic relaxation index.We found that individual mechanical properties of a tablet's excipients greatly control the materials' deformation behaviour during tablet production despite of numerous other processes occurring during compression in the tablet die such as friction, bonding and local mechanical stress.