Investigation of elastic powder properties using analytical powder decompression : Effects of tablet compaction parameters, pressure, speed, and lubrication

Aim: The objective of this project was to use analytical powder decompression (APDC) in tablet compaction processes to study the elastic behavior of powders. Background: During powder compaction, the particles undergo four stages of rearrangement, plastic deformation or particle fracture, and elastic deformation. The analytical powder compression protocol considers the loading phase and the elastic deformation during the unloading phase is neglected (Nordström et al., 2012). Using APDC analysis may give access to the underlying elastic characteristics of powders including tablet elastic recovery and powder modulus of elasticity (Persson et al., 2018). Methods: Two materials with different elasticity properties, NaCl and maize starch, were selected. After standard powder characterization, the powders were used in tablet compaction experiments with various pressures, compression and decompression rates, and lubrication. The resulting powder elastic modulus (EM) and tablet elastic recovery during unloading (ERin-die) and after ejection (ERout-of-die) up to 24 h were evaluated. Results: EM for NaCl was reduced by increased pressure or addition of internal lubrication, but no impact was seen from the compaction speeds. ERin-die for NaCl was doubled by the internal lubrication. For maize starch, EM increased at higher pressure, but it was not affected by the speeds or internal lubrication. ERout-of-die was negligible for NaCl, but it increased for maize starch with time. Conclusion: The larger nonlinear profile during unloading for maize starch can be a sign of mixed elastic and inelastic phenomena. The ascending trend for EM vs pressure for maize starch can be attributed to a larger interparticle cohesion and lower porosity. Addition of internal lubrication to NaCl lowered the tablet strengths which led to extensive relaxation and therefore much larger ERin-die