1.
Fichtner, Frauke, et al.
(författare)
Effect of surface energy on powder compactibility
2008
Ingår i: Pharmaceutical research. - : Springer Science and Business Media LLC. - 0724-8741 .- 1573-904X. ; 25:12, s. 2750-9
Tidskriftsartikel (refereegranskat) abstract
PURPOSE: The influence of surface energy on the compactibility of lactose particles has been investigated. MATERIALS AND METHODS: Three powders were prepared by spray drying lactose solutions without or with low proportions of the surfactant polysorbate 80. Various powder and tablet characterisation procedures were applied. The surface energy of the powders was characterized by Inverse Gas Chromatography and the compressibility of the powders was described by the relationship between tablet porosity and compression pressure. The compactibility of the powders was analyzed by studying the evolution of tablet tensile strength with increasing compaction pressure and porosity. RESULTS: All powders were amorphous and similar in particle size, shape, and surface area. The compressibility of the powders and the microstructure of the formed tablets were equal. However, the compactibility and dispersive surface energy was dependent of the composition of the powders. CONCLUSION: The decrease in tablet strength correlated to the decrease in powder surface energy at constant tablet porosities. This supports the idea that tablet strength is controlled by formation of intermolecular forces over the areas of contact between the particles and that the strength of these bonding forces is controlled by surface energy which, in turn, can be altered by the presence of surfactants.
2.
Frenning, Göran, et al.
(författare)
Spectral analysis of force fluctuations during probe penetration into cohesive powders
2008
Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 187:1, s. 62-67
Tidskriftsartikel (refereegranskat) abstract
We investigate force fluctuations during probe penetration into cohesive powders consisting of ∼5 μm lactose particles with varying surfaceproperties prepared by spray drying. The results obtained for the more cohesive powders were remarkably similar to those previously reported fororders of magnitude larger noncohesive particles. For the less cohesive powders, the spectral densities were instead found to exhibit two distinctpower-law regions. Furthermore, the spectra were found to be independent of the geometry of the penetrating probe and dimensions of the diecavity. These findings suggest that the response is dominated by particle aggregate or agglomerate movement for the more cohesive powders,whereas the behaviour of the less cohesive ones is consistent with a response dominated by relatively weak force chains, with the fluctuations resulting from the recurring creation and collapse of jammed states being damped for length scales N0.1 mm.
