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the role of intra-granular porosity in powder compaction - sciencedirect

the role of intra-granular porosity in powder compaction - sciencedirect

A common property of direct-compression (DC) tabletting vehicles used in the pharmaceutical industry is high intra-granular porosity. This high porosity leads to increased interparticulate friction on compaction and subsequently an increased extent of bonding compared with the compaction of the parent crystals. Granules formed by the irreversible agglomeration of ground particles in a rotary ball mill exhibit considerably higher porosity and friability leading to stronger compact strength than DC vehicles of the same compound that do not contain a binder. This effect is limited, as increased surface area leads to increased elastic deformation and bond breakage during subsequent elastic recovery. Consequently, optimum energy of compaction utilization in the production of strong tablets is obtained when materials possessing high intra-granular porosity are combined with an efficient binder.

anomalous particle size shift during post-milling storage | springerlink

anomalous particle size shift during post-milling storage | springerlink

Crystallised and ball-milled adipic acid were stored under different humidity conditions. Analyses were carried out to characterise changes in particle size distribution (laser diffraction), morphology (SEM), bulk flow properties (annular shear tester), surface adhesion forces (AFM) and crystallinity (PXRD and DVS).

It was observed that the particle size distribution of milled adipic acid can shift to finer fractions, remain unchanged, or even shift to coarser fractions depending on storage conditions. SEM analysis showed that milled adipic acid is composed of agglomerates, which can undergo de-aggregation or further agglomeration via re-crystallisation. Empirical analysis ruled out the effects of electrostatic charges on the particle size shift. In addition, an improvement in powder flow in terms of bulk tensile strength was seen for milled adipic acid stored under high relative humidity but not under low humidity.

Storage of milled adipic acid below the critical relative humidity led to localised disintegration from the agglomerate surface and particle size reduction, which was not influenced by moisture sorption or loss. This evidence supports that stress relaxation mechanism behind particle breakage of post-milled particles. Appropriate storage conditions are important in maintaining the stability of milled powders.

M. D. Ticehurst, P. A. Basford, C. I. Dallman, T. M. Lukas, P. V. Marshall, G. Nichols, and D. Smith. Characterisation of the influence of micronisation on the crystallinity and physical stability of revatropate hydrobromide. Int. J. Pharm. 193:247259 (2000).

L. Mackin, S. Sartnurak, I. Thomas, and S. Moore. The impact of low levels of amorphous material (<5%) on the blending characteristics of a direct compression formulation. Int. J. Pharm. 231:213226 (2002).

L. Mackin, R. Zanon, J. M. Park, K. Foster, H. Opalenik, and M. Demonte. Quantification of low levels (<10%) of amorphous content in micronised active batches using dynamic vapour sorption and isothermal microcalorimetry. Int. J. Pharm. 231:227236 (2002).

P. Begat, P. M. Young, S. Edge, J. S. Kaerger, and R. Price. The effect of mechanical processing on surface stability of pharmaceutical powders: visualization by atomic force microscopy. J. Pharm. Sci. 92:611619 (2003).

K. Y. Chow, J. Go, M. Mehdizadeh, and D. J. W. Grant. Modification of adipic acid crystals: influence of growth in the presence of fatty acid additives on crystal properties. Int. J. Pharm. 20:324 (1984).

G. Steele. Preformulation as an aid to product design in early drug development. In M. Gibson (ed.), Pharmaceutical Preformulation and Formulation: A Practical Guide from Candidate Drug Selection to Commercial Dosage Form, Interpharm/CRC, Boca Raton, 2004, pp. 175289.

T. R. Keel, C. Thompson, M. C. Davies, S. J. B. Tendler, and C. J. Roberts. AFM studies of the crystallization and habit modification of an excipient material, adipic acid. Int. J. Pharm 280:185198 (2004).

T. E. Tarara, M. S. Hartman, H. Gill, A. A. Kennedy, and J. G. Weers. Characterization of suspension-based metered dose inhaler formulations composed of spray dried budesonide microcrystals dispersed in HFA-134a. Pharm. Res. 21:16071614 (2004).

The authors would like to thank Junwei, Chin Lee, Ron Lim, Ai Tee, Prashant, Lay Yong, Gary Liu and Wenyi for their contribution in particle characterisation and Aaron Yuen for assisting in theoretical calculations.

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