title: Study of radial die-wall pressure changes during pharmaceutical powder compaction.
abstract: BACKGROUND
  In tablet manufacturing, less attention is paid to the measurement of die-wall pressure than to force-displacement diagrams.
  
  
  OBJECTIVE
  Therefore, the aim of this study was to investigate radial stress change during pharmaceutical compaction.
  
  
  METHODS
  The Presster(TM), a tablet-press replicator, was used to characterize compaction behavior of microcrystalline cellulose (viscoelastic), calcium hydrogen phosphate dihydrate (brittle), direct compressible mannitol (plastic), pre-gelatinized starch (plastic/elastic), and spray dried lactose monohydrate (plastic/brittle) by measuring radial die-wall pressure; therefore powders were compacted at different (pre) compaction pressures as well as different speeds. Residual die-wall pressure (RDP) and maximum die-wall pressure (MDP) were measured. Various tablet physical properties were correlated to radial die-wall pressure.
  
  
  CONCLUSIONS
  With increasing compaction pressure, RDP and MDP (P < 0.0001) increased for all materials, with increasing precompaction RDP decreased for plastic materials (P < 0.05), whereas with increasing speed MDP decreased for all materials (P < 0.05). During decompression, microcrystalline cellulose and pre-gelatinized starch showed higher axial relaxation, whereas mannitol and lactose showed higher radial relaxation, calcium hydrogen phosphate showed high axial and radial relaxations. Plastic and brittle materials showed increased tendencies for friction because of high radial relaxation.
  
  
  CONCLUSIONS
  Die-wall monitoring is suggested as a valuable tool for characterizing compaction behavior of materials and detecting friction phenomena in the early stage of development.
authors: Department of Pharmaceutical Sciences, Industrial Pharmacy Research Group, University of Basel, Mülhauser Street 51, Basel, Switzerland.
authors: Sameh
authors: S
authors: Abdel-Hamid
authors: Gabriele
authors: G
authors: Betz
mesh_terms: D011208:Powders / Q000737:chemistry; D011312:Pressure; D013607:Tablets; D013678:Technology, Pharmaceutical
chemical_list: D011208:Powders; D013607:Tablets