1.
Alderborn, Göran, et al.
(författare)
Mechanical strength of tablets
2008. - 3
Ingår i: Pharmaceutical Dosage Forms. - New York : Informa Healthcare. - 9780849390166 - 0849390168
Bokkapitel (övrigt vetenskapligt/konstnärligt)
2.
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.
3.
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.
4.
Nordström, Josefina, 1977-
(författare)
Compression analysis as a tool for technical characterization and classification of pharmaceutical powders
2008
Doktorsavhandling (övrigt vetenskapligt/konstnärligt) abstract
There are today strong incentives for an increased understanding of material properties and manufacturing processes to facilitate the development of new technologies in the pharmaceutical industry. The purpose of this thesis was to suggest methods requiring a low sample amount for characterization of technical properties of powders.Compression analysis was used to evaluate the formulation relevance of some compression equations. Using the mechanics of single granules to estimate powder functionality was part of this work. It was concluded that the formability of granular solids and the plasticity of single granules could be determined with compression analysis by using the Kawakita model for single components and binary mixtures of ductile granules.Further on, the fragmentation propensity of solid particles could be estimated from compression analysis by using the Shapiro equation, enabling indicators of both the fragmentation and the deformation propensity of particles to be derived in one single compression test.The interpretations of the compression parameters were only valid if the influence of particle rearrangement was negligible for the overall compression profile. An index indicating the extent of particle rearrangement was developed and a classification system of powders into groups dependent on the incidence of particle rearrangement was suggested as tools to enable rational interpretations of compression parameters.The application of compression analysis was demonstrated by investigating the relevance of the mechanics of granular solids for their tableting abilities. The plasticity of single gran-ules was suggested to influence both the rate of compactibility and the mode of deformation, and consequently the maximal tablet strength. The degree of granule bed deformation was shown to be a potential in line process indicator to describe the tableting forming ability.This thesis contributes to a scheme, suitable in formulation work and process control, to describe manufacturability of powders for an enhanced tablet formulation technology.
5.
Nordström, Josefina, et al.
(författare)
On the physical interpretation of the Kawakita and Adams parameters derived from confined compression of granular solids
2008
Ingår i: Powder Technology. - : Elsevier BV. - 0032-5910 .- 1873-328X. ; 182:3, s. 424-435
Tidskriftsartikel (refereegranskat) abstract
The objective of this paper was to investigate the physical significance of the Kawakita and Adams parameters derived from the compressionof some granular solids. Four model granules of different expected deformation behaviour were prepared by varying the composition and porosityof the granules. The granules were nearly spherical and of similar size and showed a variation in mechanical properties in terms of their elasticity,plasticity, fracture strength and brittleness. Due to the size and shape of the granules, compression due to granule rearrangement was generallylimited. The Kawakita a parameter approximated the maximal engineering strain of the granular solids and both the Kawakita a and b−1parameter reflected the plasticity of the granules. The Adams parameter τ0 seemed to reflect the initial cracking of granules. Thus, the combineduse of the Kawakita parameters a and b−1 and the Adams parameter τ0 may give a comprehensive representation of the compression behaviour ofgranular solids.
6.
Nordström, Josefina, et al.
(författare)
On the role of granule yield strength for the compactibility of granular solids
2008
Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0022-3549 .- 1520-6017. ; 97:11, s. 4807-4814
Tidskriftsartikel (refereegranskat) abstract
The objective of this article was to explore the relationship between mechanical properties of single granules and the evolution in tensile strength and tablet micro-structure. Granules of different expected deformation behavior were used as model materials. It is suggested that the role of plasticity in this context is twofold: firstly, to affect the rate of compactibility and thus the pressure range needed to reach the maximal attained tablet strength and, secondly, to affect the mode of deformation of the granules and thus the maximal attained tablet strength. A decrease in yield pressure of single granules increased the tablet tensile strength at a given compaction pressure. The yield pressure can be controlled by the granule composition and porosity.
