Davies, Peter Neil;
(1992)
The influence of shape on the strength of tablets.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
The effect of the compact perimeter shape on the compressional properties of pharmaceutical excipients has been examined. Compacts of a deforming material, Avicel PH-102 and a fragmenting material, Emcompress were prepared. The compacts were prepared on single punch and rotary machines using flat faced circular, hexagonal and square tooling. The mechanical strengths of the compacts were determined using the diametral compression test and an axial compression test. The validity of using the diametral compression test for shaped compacts was assessed using shaped casts of gypsum. It was shown that with the appropriate selection of platens the test could reliably induce tensile failure in square and hexagonal specimens as well as in conventional circular specimens. The diametral compression test did not reveal any differences in the tensile strengths of different shaped compacts prepared with the same compaction pressure. Visual inspection of Emcompress compacts did reveal flaws present on the lower surface of square compacts produced on the single punch machine that were not evident on circular compacts. Further evidence of such structural differences was seen when comparing the axial compression test results for square and circular compacts of Emcompress. The differences are due to poor force transmission at the comers of the squares and may be prevented by improving lubrication. No such differences are seen between square and circular compacts of Avicel. Large differences were detected in the compaction pressure/ tensile strength profiles of Avicel compacts produced on different tablet machines. The compacts prepared using the rotary machine had lower tensile strengths and exhibited a lower capping pressure. The pressure at which capping commenced was greater for the square compacts than the circles. The differences are attributed to the material being compressed between two moving punches on the rotary machine as opposed to one moving punch on the single punch machine.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | The influence of shape on the strength of tablets |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Thesis digitised by ProQuest. |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10124024 |
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