Dokument: The Use of a Ring Shear Tester to Evaluate the Flowability
| Titel: | The Use of a Ring Shear Tester to Evaluate the Flowability | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=14045 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20100210-112424-8 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Jaeda , Hind [Autor] | |||||||
| Dateien: |
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| Stichwörter: | Ring shear tester, Powder, Flowability | |||||||
| Dewey Dezimal-Klassifikation: | 600 Technik, Medizin, angewandte Wissenschaften » 610 Medizin und Gesundheit | |||||||
| Beschreibung: | The assessment of flowability of powdered materials in the pharmaceutical industry is a
crucial step and a prerequisite for a cheap, successful and non-time consuming production. In this work a ring shear tester was employed as a tool for the quantitative evaluation and assessment of the flowability of pharmaceutical substances and mixtures. The flowability (ffc) is represented as the ratio of the consolidation stress to the unconfined yield strength. The larger the ffc is, the better a bulk solid flows. A comparison between the large (RST-01.pc) and small (RST-XS) Schulze testers was carried out. Regardless the differences in composition, size and shape of the substances examined, comparing the ffc values of both testers showed that the results were well correlated with a correlation coefficient, r = 0.97. However, the smaller tester showed slightly lower ffc values compared to the larger tester. For comparative tests this effect did not play a role as long as the same ring shear tester with the same shear cell size was used throughout the measurements. The influence of different types of Aerosil® on the flowability of Paracetamol was investigated by means of the ring shear tester. Other conventional easy applicable methods were also employed such as; angle of repose, Hausner ratio and flow rate. It was observed that the ffc values increased with the increase of Aerosil® percentage, and then they either decreased or remained constant with further increase in percentage. Aerosil percentage about 0.5% was enough to achieve a maximum flow improvement. The angle of repose decreased as we increased the percentage of Aerosil®. The angles of repose values were inversely proportional to the ffc values. The Hausner ratio did not show agreeable results to those of the ffc. The flow rate also could not be measured for all samples, and even the samples measured did not reveal any general trend. As a conclusion the ring shear tester can be applied as a quantitative comparative test to replace other inaccurate and operator influenced conventional methods. Besides, it was observed that the capsules containing different types and percentages of Aerosil possessed lower relative standard deviation values (RSD) compared to capsulesfilled with Paracetamol alone. The capsules containing Aerosil® showed higher fill weights compared to capsules filled with paracetamol alone, where Aerosil® reduces the interparticulate forces between paracetamol particles which consequently move closer reducing the space between each other and obtaining higher densities and fill weights. However, plotting the RSD versus the ffc showed that all samples prepared with Aerosil®, which have higher ffc values, showed lower RSD values with lower scattering values compared to those prepared with Paracetamol alone. Also the flow behaviour of binary mixtures was investigated. It was found that the flow profiles (the graphical presentation of the ffc values versus the percentage of the free flowing component in the mixture) for almost all mixtures examined were represented with two curve sections. The first section indicating the slight improvement in flowability at low concentrations of the free flowing component until reaching a concentration (the point of intersection between the two curve sections), after which a significant flowability improvement - represented with the second curve section - was noticed with the further addition of the free flowing component. In such mixtures the bulk properties of the fine poor flowing components dominated the flow behaviour of the binary mixtures. The intersection point differed from a mixture to another according to the particle sizes and shapes involved in the mixtures. On the other hand mixtures with Paracetamol as the fine poor flowing component were represented with only one curve indicating the flow improvement on the addition of very small concentrations of the free flowing component i.e.; about 20 % V/V free flowing component. However, in these mixtures the flow behaviour of the free flowing components dominated the flow behaviour of the binary mixture. Regarding the packing behaviour of the mixtures two profiles were noticed according to the shape of the fine poor flowing component in the mixture. Mixtures comprising fine spherical or irregular shaped components showed a profile with a maximum packing density, after which the density decreased with the further increase of percentage of free flowing component. Mixturescomprising fine needle or rod shaped components yielded a profile without a maximum packing density. In the second profile the densities are additive and can be predicted from the densities and volume fractions of the binary mixture components. Generally it can be concluded that the flowability of the binary mixtures was influenced by the shape and size of both components and whether the binary mixture achieved a maximum packing density or did not was influenced mainly by the shape of the fine component in the binary mixtures. However, the concentration at which maximum packing occurred depended on both parameters of each component. The flow behaviour of lipids in the presence and absence of Aerosil® was also examined. Most pharmaceutical substances investigated in this work established a maximum flow improvement with only 0.5% Aerosil, while lipids showed a different behaviour. The easy flowing lipids (ffc > 4) required percentages of Aerosil higher than 0.5% to achieve the intended flow improvement. However, the poor flowing lipids (ffc < 4) showed two different behaviours as observed in this study. They either showed significant flow improvement with 2% Aerosil (believed to decrease flowability of other substances as seen in paracetamol section), or did not show flow improvement even with very high concentrations of Aerosil i.e.; up to 15%. Comparing the influence of Aerosil on the flow behaviour of lipids with those observed in section 3.2 (influence of Aerosil on flow behaviour of Paracetamol), it may be high-lighted that besides the specific surface area, shape, size and surface morphology of substances, the hydrophobic nature of lipids plays an important role on the flow enhancing property of the glidant. This role differs from one lipid to another according to its degree of hydrophobicity. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät » WE Pharmazie » Pharmazeutische Technologie und Biopharmazie | |||||||
| Dokument erstellt am: | 10.02.2010 | |||||||
| Dateien geändert am: | 07.02.2010 | |||||||
| Promotionsantrag am: | 14.10.2009 | |||||||
| Datum der Promotion: | 14.12.2009 |
