title: The relation between granule size, granule stickiness, and torque in the high-shear granulation process.
abstract: OBJECTIVE
  To investigate the background of the observed relationship between measured torque and granule size in high-shear granulation processes.
  
  
  METHODS
  Torque was measured during the granulation process; the behavior of individual wet granules during compaction was investigated using micromanipulation. Surface properties of wet granules were manipulated by coating them with talc.
  
  
  RESULTS
  The torque-granule size relationship could not be explained by the rise in mass of the individual granules; it occurs rather through an increase in stickiness of the granules when the moisture content is increased. Obviously, the increased stickiness that causes the granules to grow also increases the torque. Increased stickiness was shown to be the result of an increased deformability of the granules at higher moisture contents, in combination with a change in surface properties. The elastic-plastic behavior (ratio of elastic to plastic deformation) was found to change at increasing moisture contents.
  
  
  CONCLUSIONS
  Our results imply that changes in the stickiness of the granular material that may be caused by changes in composition shift the torque-size relationship. This may be of particular importance when, for example, granulation results from placebo batches are used to predict the granule size of drug-containing batches.
authors.affiliation: Department of Pharmaceutical Technology and Biopharmacy, Groningen University Institute for Drug Exploration, Antonius Deusinglaan 1, 9713 AV, Groningen, The Netherlands. a.bouwman@farm.rug.nl
authors.forename: A M
authors.initials: AM
authors.lastname: Bouwman
authors.forename: M J
authors.initials: MJ
authors.lastname: Henstra
authors.forename: J J M E
authors.initials: JJ
authors.lastname: Hegge
authors.forename: Z
authors.initials: Z
authors.lastname: Zhang
authors.forename: A
authors.initials: A
authors.lastname: Ingram
authors.forename: J P K
authors.initials: JP
authors.lastname: Seville
authors.forename: H W
authors.initials: HW
authors.lastname: Frijlink
mesh_terms: D010316:Particle Size; D033081:Shear Strength; D013678:Technology, Pharmaceutical / Q000295:instrumentation* / Q000379:methods*; D019415:Torque