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Investigations of single microcrystalline cellulose-based granules subjected to confined triaxial compression
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
2016 (English)In: Powder Technology, ISSN 0032-5910, E-ISSN 1873-328X, Vol. 289, p. 79-87Article in journal (Refereed) Published
Resource type
Text
Abstract [en]

Confined triaxial compression of single granules was performed in order to assess the contact force development and modes of granule deformation under these conditions. In the study, four microcrystalline cellulose-based granule types of different characteristics were investigated. Results from triaxial single-granule compression experiments were evaluated using an analytical model as well as by comparison to unconfined single-granule compression and to confined bulk compression experiments. It was observed that single granules deform and densify, but tend to keep their integrity during confined triaxial compression, as evident from both compression data and from morphological analysis. Results from confined single granule compression were well represented by the analytical model. These results also largely reflected those from bulk compression experiments, including features of the force-displacement curves as well as rank order between the granule types in terms of contact stiffness. Furthermore, it was shown that intragranular porosity to a high extent governs the onset of plastic incompressibility.

Place, publisher, year, edition, pages
2016. Vol. 289, p. 79-87
Keywords [en]
Compression, Triaxial, Hydrostatic, Single granules, Confined conditions, Contact mechanics
National Category
Pharmaceutical Sciences
Identifiers
URN: urn:nbn:se:uu:diva-280895DOI: 10.1016/j.powtec.2015.11.051ISI: 000370095400012OAI: oai:DiVA.org:uu-280895DiVA, id: diva2:912338
Funder
Swedish Research Council, 621-2011-4049Available from: 2016-03-16 Created: 2016-03-16 Last updated: 2018-04-12Bibliographically approved
In thesis
1. Confined Compression of Single Particles: Development of a Novel Triaxial Testing Instrument and Particle-Scale Modelling
Open this publication in new window or tab >>Confined Compression of Single Particles: Development of a Novel Triaxial Testing Instrument and Particle-Scale Modelling
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

When predicting the performance of a powder compaction process, assessing the behaviour of the particles comprising the powder bed is of central relevance. Currently, however, no experimental methods are available for mimicking the multiaxial loading conditions imposed on the individual particles in a powder bed during compaction, and such analyses are therefore usually performed in silico. Thus, the purpose of this thesis is to introduce a novel experimental method that enables experimental evaluation of confined triaxial loading conditions on individual particles in the mm-scale.

The work underlying the thesis consists of three major parts. Firstly, the triaxial instrument was designed and developed, after which its performance was evaluated using nominally ideal elastic-plastic spheres as model materials. These initial experiments showed that the instrument was able to successfully impose confined triaxial conditions on the particles, something that was verified by finite element method (FEM) simulations.

Secondly, the triaxial instrument was used to investigate differences in deformation characteristics under uniaxial and triaxial loading conditions for four different microcrystalline cellulose (MCC)-based granules. It was shown that fragmentation, associated with unconfined uniaxial compression, was impeded under confined triaxial conditions, despite the emergence of cracks. In addition, it was observed that the primary crack always occurs in a plane parallel to the most deformed direction, and that the location of the largest pore has a pronounced influence on the path of the crack.

Thirdly, the influence of different triaxial loading ratios were evaluated on polymer spheres, after which a unified description of contact pressure development was devised. Data from these experiments were then successfully used to calibrate a contact model for simulating bulk powder compression with the discrete element method (DEM).

All in all, a novel experimental method has been established, which has proven useful as an alternative and complement to numerical studies when studying single particle deformation under confined triaxial conditions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 58
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 255
Keywords
Powder compaction, Compression, Single particle, Particle mechanics, Powder mechanics, Confined conditions, Triaxial, Apparatus design, Modelling
National Category
Pharmaceutical Sciences
Research subject
Pharmaceutics
Identifiers
urn:nbn:se:uu:diva-348091 (URN)978-91-513-0329-1 (ISBN)
Public defence
2018-10-31, B21, BMC, Husargatan 3, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-05-09 Created: 2018-04-12 Last updated: 2018-10-08

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Jonsson, HenrikFrenning, Göran

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