Thesis
The role of tablet shape in the structural integrity of bilayer tablets during compaction and ejection
Master of Science (M.S.), Drexel University
Jul 2011
DOI:
https://doi.org/10.17918/00010134
Abstract
Bilayer tablet production faces many challenges dviring the tablet manufacturing process (compaction, unloading, and ejection). The main physical failure is delamination, but even micro cracking will have a significant effect on the integrity of the tablet after the maniffacturing process or on the consumer perception of quality. Prior work on flat tablets has highlighted some of the important issues that affect the mechanical performance of bilayer tablets. The majority of tablets are manufactured with a cvirvature to allow for ease of swallowing and meet production standards such as minimum strength. The use of concave punches changes the mechanics of compaction and alters the local stress state during imloading and ejection. Extensive tablet experiments were used to evaluate standard concave bilayer tablets made of a model pair of pharmaceutical excipients: microciystalline cellulose (MCC) and bibasic calcium phosphate (DCP). The tablets were evaluated by visual inspection, x-ray tomography, scanning electron microscopy, and optical microscopy. Visual inspection clearly showed that results from flat tablets cannot be transferred to curved tablets. The transition to a bilayer tablet produced a weaker or stronger tablet depending on tablet sequence. X-ray tomography provided information on surface and internal cracks where samples with no visible cracks were found to have cracks along the interface near the free surface. SEM imaging also provided rich surface detail, but drying of the samples within the sample chamber yielded biased results. Optical microscopy experiments with an extended field of view were promising but the results were very sensitive to lighting. The traditional models used for tableting simulations carmot predict the unloading behavior of powder compacts nor can they achieve numerical convergence due to difference in material parameters between layers. A rough model which attempted to estimate the effect of differential expansion of the two layers was pursued with mixed results. These results are the first step toward obtaining an in depth understanding of the design and optimization of bilayer tablets.
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Details
- Title
- The role of tablet shape in the structural integrity of bilayer tablets during compaction and ejection
- Creators
- Carly Lynn Snyder
- Contributors
- Antonios Zavaliangos (Advisor) - Drexel University, Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xii, 103 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) (1970-2026); College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991021889083404721