Effects of particle surface roughness on in-die flow and tableting behavior of lactose

Particle rearrangement takes place during the initial phase of tablet compaction. In this study, rough lactose particles were prepared by roller compaction, and their surface roughness modified by partial surface dissolution using a fluidized bed processor. Flow characteristics of the particles were determined using various flow methods, and their compaction characteristics studied using a compaction simulator with punches of different geometry and compaction pressure. Rougher particles demonstrated poorer compressibility and powder flow due to the higher interparticulate frictional forces required for particle movement. Rearrangement energy during tablet compaction was found to be correlated with compressibility (R² = 0.92) and increased with surface roughness of the particles. Particle rearrangement was found to be dependent on interparticulate frictional forces, which could be measured using FT4 powder rheometer variable flow rate test and compressibility test. Plastic energy decreased as a result of the increased rearrangement energy requirements. Decrease in tensile strength as a result of decrease in plastic energy was not significantly different. Roller-compacted lactose particles produced tablets of higher tensile strength than crystalline lactose because of prefragmentation of the crystalline structure during roller compaction.