Compression characteristics of granulated materials: VI. Pore size distributions, assessed by mercury penetration, of compacts of two lactose granulations with different fragmentation propensities

Abstract

Tablets were compacted at a pressure of 50 MPa from two granulations which had identical composition (95% lactose and 5% PVP) but different physical properties, i.e., porosity, compressive strength and fragmentation propensity during compaction. The pore system of the tablets was assessed by mercury penetration measurements. A bimodal distribution in pore size was observed for compacts made from the granulation with the lower fragmentation propensity, while a unimodal and comparatively narrower pore size distribution was found for compacts made from the granulation with the higher fragmentation propensity. Thus, it was concluded that a tablet compacted from granules has a pore structure consisting of inter- and intragranular pores and that the degree of fragmentation of the granules during the compression phase especially affects the size of the intergranular pores. The results support the validity of using the air permeability technique for the characterisation of granule fragmentation.