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Pore Direction in Relation to Anisotropy of Mechanical Strength in a Cubic Starch Compact

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Abstract

The purpose of this research was to evaluate the relation between preferential direction of pores and mechanical strength of cubic starch compacts. The preferential pore direction was quantified in SEM images of cross sections of starch compacts using a previously described algorithm for determination of the quotient of transitions (Q). This parameter and the mechanical strength were evaluated in compacts of different porosities. Starch was chosen as a model compound for materials with ductile behaviour of which tablets with low porosities can be made and which shows some elastic recovery after compaction. At medium and high porosity Q was significantly higher in the images providing a side view of the compact than in the images providing a top view (0.973 vs. 0.927 and 0.958 vs. 0.874 at 0 mm from the side of the compact and 0.956 vs. 0.854 and 0.951 vs. 0.862 at 3.5 mm), indicating that the pores were mainly oriented in the direction perpendicular to the direction of compression. This was accompanied by a lower crushing force in this direction. This could be explained by considering the pores as cracks which propagate through the sample during crushing. For both directions the crushing force decreased with increasing porosity. The yield strength of the compacts also decreased with increasing porosity, but this parameter was not dependent on the direction of crushing when the porosity was below 10%. The results show that pore direction significantly influences the crushing force but does not influence the yield strength, at porosities below 10%.

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Authors and Affiliations

  1. Department of Pharmaceutical Technology and Biopharmacy, University of Groningen, Groningen, The Netherlands

    Yu San Wu, Henderik W. Frijlink & Kees van der Voort Maarschalk

  2. Quantitative Imaging Group, Department of Imaging Science & Technology, Faculty of Applied Sciences, Delft University of Technology, Delft, The Netherlands

    Lucas J. van Vliet

  3. Laboratory for Cell Biology and Electron Microscopy, University of Groningen, Groningen, The Netherlands

    Ietse Stokroos

  4. Department of Pharmaceutics, NV Organon, part of Schering-Plough, Oss, The Netherlands

    Kees van der Voort Maarschalk

  5. Solvay Pharmaceuticals, Building WNH, C.J. van Houtenlaan 36, 1381 CP, Weesp, The Netherlands

    Yu San Wu

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  1. Yu San Wu
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  2. Lucas J. van Vliet
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  3. Henderik W. Frijlink
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  4. Ietse Stokroos
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  5. Kees van der Voort Maarschalk
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Correspondence to Yu San Wu.

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Wu, Y.S., van Vliet, L.J., Frijlink, H.W. et al. Pore Direction in Relation to Anisotropy of Mechanical Strength in a Cubic Starch Compact. AAPS PharmSciTech 9, 528–535 (2008). https://doi.org/10.1208/s12249-008-9074-4

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  • DOI: https://doi.org/10.1208/s12249-008-9074-4

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