Characterization of Mechanical Property Distributions on Tablet Surfaces
Powder densification through uniaxial compaction is governed by a number of simultaneous processes taking place on a reduced time as the result of the stress gradients within the packing, as well as the frictional and adhesive forces between the powder and the die walls. As a result of that, a densi...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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MDPI AG
2018-10-01
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| Series: | Pharmaceutics |
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| Online Access: | http://www.mdpi.com/1999-4923/10/4/184 |
| _version_ | 1811279925258223616 |
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| author | Ramon Cabiscol Jan Henrik Finke Harald Zetzener Arno Kwade |
| author_facet | Ramon Cabiscol Jan Henrik Finke Harald Zetzener Arno Kwade |
| author_sort | Ramon Cabiscol |
| collection | DOAJ |
| description | Powder densification through uniaxial compaction is governed by a number of simultaneous processes taking place on a reduced time as the result of the stress gradients within the packing, as well as the frictional and adhesive forces between the powder and the die walls. As a result of that, a density and stiffness anisotropy is developed across the axial and radial directions. In this study, microindentation has been applied to assess and quantify the variation of the module of elasticity ( E m o d ) throughout the surface of cylindrical tablets. A representative set of deformation behaviors was analyzed by pharmaceutical excipients ranging from soft/plastic behavior (microcrystalline cellulose) over medium (lactose) to hard/brittle behavior (calcium phosphate) for different compaction pressures. The results of the local stiffness distribution over tablet faces depicted a linear and directly proportional tendency between a solid fraction and E m o d for the upper and lower faces, as well as remarkable stiffness anisotropy between the axial and radial directions of compaction. The highest extent of the stiffness anisotropy that was found for ductile grades of microcrystalline cellulose (MCC) in comparison with brittle powders has been attributed to the dual phenomena of overall elastic recovery and Poisson’s effect on the relaxation kinetics. As a reinforcement of this analysis, the evolution of the specific surface area elucidated the respective densification mechanism and its implementations toward anisotropy. For ductile excipients, the increase in the contact surface area as well as the reduction and closing of interstitial pores explain the reduction of surface area with increasing compaction pressure. For brittle powders, densification evolves through fragmentation and the subsequent filling of voids. |
| first_indexed | 2024-04-13T01:05:53Z |
| format | Article |
| id | doaj.art-b98b990e0ead4b03a65a656d3e2d455a |
| institution | Directory Open Access Journal |
| issn | 1999-4923 |
| language | English |
| last_indexed | 2024-04-13T01:05:53Z |
| publishDate | 2018-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Pharmaceutics |
| spelling | doaj.art-b98b990e0ead4b03a65a656d3e2d455a2022-12-22T03:09:22ZengMDPI AGPharmaceutics1999-49232018-10-0110418410.3390/pharmaceutics10040184pharmaceutics10040184Characterization of Mechanical Property Distributions on Tablet SurfacesRamon Cabiscol0Jan Henrik Finke1Harald Zetzener2Arno Kwade3Institute for Particle Technology (iPAT), Technische Universität Braunschweig, 38104 Braunschweig, GermanyInstitute for Particle Technology (iPAT), Technische Universität Braunschweig, 38104 Braunschweig, GermanyInstitute for Particle Technology (iPAT), Technische Universität Braunschweig, 38104 Braunschweig, GermanyInstitute for Particle Technology (iPAT), Technische Universität Braunschweig, 38104 Braunschweig, GermanyPowder densification through uniaxial compaction is governed by a number of simultaneous processes taking place on a reduced time as the result of the stress gradients within the packing, as well as the frictional and adhesive forces between the powder and the die walls. As a result of that, a density and stiffness anisotropy is developed across the axial and radial directions. In this study, microindentation has been applied to assess and quantify the variation of the module of elasticity ( E m o d ) throughout the surface of cylindrical tablets. A representative set of deformation behaviors was analyzed by pharmaceutical excipients ranging from soft/plastic behavior (microcrystalline cellulose) over medium (lactose) to hard/brittle behavior (calcium phosphate) for different compaction pressures. The results of the local stiffness distribution over tablet faces depicted a linear and directly proportional tendency between a solid fraction and E m o d for the upper and lower faces, as well as remarkable stiffness anisotropy between the axial and radial directions of compaction. The highest extent of the stiffness anisotropy that was found for ductile grades of microcrystalline cellulose (MCC) in comparison with brittle powders has been attributed to the dual phenomena of overall elastic recovery and Poisson’s effect on the relaxation kinetics. As a reinforcement of this analysis, the evolution of the specific surface area elucidated the respective densification mechanism and its implementations toward anisotropy. For ductile excipients, the increase in the contact surface area as well as the reduction and closing of interstitial pores explain the reduction of surface area with increasing compaction pressure. For brittle powders, densification evolves through fragmentation and the subsequent filling of voids.http://www.mdpi.com/1999-4923/10/4/184indentationtabletsinhomogeneityBETporosity |
| spellingShingle | Ramon Cabiscol Jan Henrik Finke Harald Zetzener Arno Kwade Characterization of Mechanical Property Distributions on Tablet Surfaces Pharmaceutics indentation tablets inhomogeneity BET porosity |
| title | Characterization of Mechanical Property Distributions on Tablet Surfaces |
| title_full | Characterization of Mechanical Property Distributions on Tablet Surfaces |
| title_fullStr | Characterization of Mechanical Property Distributions on Tablet Surfaces |
| title_full_unstemmed | Characterization of Mechanical Property Distributions on Tablet Surfaces |
| title_short | Characterization of Mechanical Property Distributions on Tablet Surfaces |
| title_sort | characterization of mechanical property distributions on tablet surfaces |
| topic | indentation tablets inhomogeneity BET porosity |
| url | http://www.mdpi.com/1999-4923/10/4/184 |
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